TY  - JOUR
AU  - Stojanović, Jevrem
AU  - Krmar, Jovana
AU  - Otašević, Biljana
AU  - Protić, Ana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4976
AB  - High-pressure liquid chromatography (HPLC) is a technique of paramount importance in
the analysis of pharmaceuticals because of its ability to separate moderately polar to less polar
compounds, such as drugs and related substances. The concept of green analytical chemistry
(GAC) aims to provide more environmentally friendly and safer analytical methods in terms of
reagents, energy, and waste. One of the major challenges of GAC is to find an appropriate
approach to evaluate the greenness of analytical methods. An extension of GAC, called white
analytical chemistry (WAC), has been introduced to consider not only environmental friendliness,
but also other aspects that contribute to the sustainability of methods, such as analytical and
economic or practical efficiency. HPLC methods are intrinsically not green, due to the high
consumption of toxic organic solvents and the resulting generation of large amounts of toxic
waste. Fortunately, there are many approaches to overcome the non-green character of HPLC
methods. In this article, various modifications of the HPLC methods that increase its
environmental friendliness are presented, as well as the various tools used to evaluate
environmental friendliness. In addition, the new concept of white analytical chemistry is
presented.
AB  - Tečna hromatografija pod visokim pritiskom (HPLC) je tehnika od ogromne važnosti u analitici lekova zbog svoje mogućnosti da razdvoji umereno do manje polarna jedinjenja, kao što su aktivne farmaceutske i srodne supstance. Koncept zelene analitičke hemije (GAC) ima za cilj da obezbedi ekološki prihvatljivije i bezbednije metode u pogledu reagenasa, energije i otpada. Jedan od glavnih izazova GAC je da pronađe odgovarajući pristup za procenu "zelenosti" analitičkih metoda. Proširenje GAC, nazvano bela analitička hemija (WAC), uvedeno je kako bi se uzela u obzir ne samo ekološka prihvatljivost, već i drugi aspekti koji doprinose održivosti metoda, kao što su analitička i ekonomska ili praktična efikasnost. HPLC metode suštinski nisu "zelene" zbog obimne potrošnje toksičnih organskih rastvarača i posledičnog stvaranja velikih količina toksičnog otpada. Srećom, postoji mnogo pristupa za prevazilaženje ne-zelene prirode HPLC metoda. U ovom radu su predstavljene različite modifikacije HPLC metode koje povećavaju ekološku prihvatljivost, kao i različiti alati koji se koriste za procenu ekološke prihvatljivosti. Pored toga, predstavljen je novi koncept bele analitičke hemije.
PB  - Savez farmaceutskih udruženja Srbije (SFUS)
T2  - Arhiv za farmaciju
T1  - Resource management in HPLC: Unveiling a green face of pharmaceutical analysis
T1  - Upravljanje resursima u HPLC: Otkrivanje zelenog lica farmaceutske analize
VL  - 73
IS  - 2
SP  - 146
EP  - 171
DO  - 10.5937/arhfarm73-43479
ER  - 

@article{
author = "Stojanović, Jevrem and Krmar, Jovana and Otašević, Biljana and Protić, Ana",
year = "2023",
abstract = "High-pressure liquid chromatography (HPLC) is a technique of paramount importance in
the analysis of pharmaceuticals because of its ability to separate moderately polar to less polar
compounds, such as drugs and related substances. The concept of green analytical chemistry
(GAC) aims to provide more environmentally friendly and safer analytical methods in terms of
reagents, energy, and waste. One of the major challenges of GAC is to find an appropriate
approach to evaluate the greenness of analytical methods. An extension of GAC, called white
analytical chemistry (WAC), has been introduced to consider not only environmental friendliness,
but also other aspects that contribute to the sustainability of methods, such as analytical and
economic or practical efficiency. HPLC methods are intrinsically not green, due to the high
consumption of toxic organic solvents and the resulting generation of large amounts of toxic
waste. Fortunately, there are many approaches to overcome the non-green character of HPLC
methods. In this article, various modifications of the HPLC methods that increase its
environmental friendliness are presented, as well as the various tools used to evaluate
environmental friendliness. In addition, the new concept of white analytical chemistry is
presented., Tečna hromatografija pod visokim pritiskom (HPLC) je tehnika od ogromne važnosti u analitici lekova zbog svoje mogućnosti da razdvoji umereno do manje polarna jedinjenja, kao što su aktivne farmaceutske i srodne supstance. Koncept zelene analitičke hemije (GAC) ima za cilj da obezbedi ekološki prihvatljivije i bezbednije metode u pogledu reagenasa, energije i otpada. Jedan od glavnih izazova GAC je da pronađe odgovarajući pristup za procenu "zelenosti" analitičkih metoda. Proširenje GAC, nazvano bela analitička hemija (WAC), uvedeno je kako bi se uzela u obzir ne samo ekološka prihvatljivost, već i drugi aspekti koji doprinose održivosti metoda, kao što su analitička i ekonomska ili praktična efikasnost. HPLC metode suštinski nisu "zelene" zbog obimne potrošnje toksičnih organskih rastvarača i posledičnog stvaranja velikih količina toksičnog otpada. Srećom, postoji mnogo pristupa za prevazilaženje ne-zelene prirode HPLC metoda. U ovom radu su predstavljene različite modifikacije HPLC metode koje povećavaju ekološku prihvatljivost, kao i različiti alati koji se koriste za procenu ekološke prihvatljivosti. Pored toga, predstavljen je novi koncept bele analitičke hemije.",
publisher = "Savez farmaceutskih udruženja Srbije (SFUS)",
journal = "Arhiv za farmaciju",
title = "Resource management in HPLC: Unveiling a green face of pharmaceutical analysis, Upravljanje resursima u HPLC: Otkrivanje zelenog lica farmaceutske analize",
volume = "73",
number = "2",
pages = "146-171",
doi = "10.5937/arhfarm73-43479"
}

Stojanović, J., Krmar, J., Otašević, B.,& Protić, A.. (2023). Resource management in HPLC: Unveiling a green face of pharmaceutical analysis. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije (SFUS)., 73(2), 146-171.
https://doi.org/10.5937/arhfarm73-43479

Stojanović J, Krmar J, Otašević B, Protić A. Resource management in HPLC: Unveiling a green face of pharmaceutical analysis. in Arhiv za farmaciju. 2023;73(2):146-171.
doi:10.5937/arhfarm73-43479 .

Stojanović, Jevrem, Krmar, Jovana, Otašević, Biljana, Protić, Ana, "Resource management in HPLC: Unveiling a green face of pharmaceutical analysis" in Arhiv za farmaciju, 73, no. 2 (2023):146-171,
https://doi.org/10.5937/arhfarm73-43479 . .

TY  - DATA
AU  - Krmar, Jovana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4884
AB  - Data used in mixed QSPR modeling.
The data table used for modeling includes the following key components:
1. Experimental conditions: The experimental conditions encompass parameters such as methanol (MeOH) content in the mobile phase, flow rate of the mobile phase, discharge current , sheath gas pressure and vaporizer temperature. These parameters are systematically varied within specific ranges according to the experimental plan based on the Box-Behnken design (BBD).
2. Calculated molecular descriptors: An important aspect of the data table is the pool of molecular descriptors calculated by Dragon software. These descriptors provide valuable insights into the molecular characteristics of the compounds under investigation. They aid in understanding the relationship between the compounds' structural properties and their observed APCI ionization behavior.
3. Observed response: Response (that is, dependent variable used for QSPR modeling) was acquired as signal intensity (cps) of the m/z signal from the target ionic species in selected ion monitoring (SIM) mode. The responses for each of the eight analytes were measured under 41 different experimental conditions, designed using the BBD. The studied response was sqrt-transformed to eliminate the skewness of the ion signal distribution.
PB  - University of Belgrade - Faculty of Pharmacy
T2  - Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm
T1  - Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4884
ER  - 

@misc{
author = "Krmar, Jovana",
year = "2023",
abstract = "Data used in mixed QSPR modeling.
The data table used for modeling includes the following key components:
1. Experimental conditions: The experimental conditions encompass parameters such as methanol (MeOH) content in the mobile phase, flow rate of the mobile phase, discharge current , sheath gas pressure and vaporizer temperature. These parameters are systematically varied within specific ranges according to the experimental plan based on the Box-Behnken design (BBD).
2. Calculated molecular descriptors: An important aspect of the data table is the pool of molecular descriptors calculated by Dragon software. These descriptors provide valuable insights into the molecular characteristics of the compounds under investigation. They aid in understanding the relationship between the compounds' structural properties and their observed APCI ionization behavior.
3. Observed response: Response (that is, dependent variable used for QSPR modeling) was acquired as signal intensity (cps) of the m/z signal from the target ionic species in selected ion monitoring (SIM) mode. The responses for each of the eight analytes were measured under 41 different experimental conditions, designed using the BBD. The studied response was sqrt-transformed to eliminate the skewness of the ion signal distribution.",
publisher = "University of Belgrade - Faculty of Pharmacy",
journal = "Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm",
title = "Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4884"
}

Krmar, J.. (2023). Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm. in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm
University of Belgrade - Faculty of Pharmacy..
https://hdl.handle.net/21.15107/rcub_farfar_4884

Krmar J. Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm. in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm. 2023;.
https://hdl.handle.net/21.15107/rcub_farfar_4884 .

Krmar, Jovana, "Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm" in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithm (2023),
https://hdl.handle.net/21.15107/rcub_farfar_4884 .

TY  - DATA
AU  - Krmar, Jovana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4880
AB  - Data table for model building.

The data table used for modeling includes the following key components:

1. Chromatographic conditions: The chromatographic conditions encompass parameters such as the concentration of Brij L23, the pH of the micellar component of the mobile phase, and the volume fraction of acetonitrile. These parameters are systematically varied within specific ranges according to the experimental plan based on the Box-Behnken design.

2. Calculated molecular descriptors: An important aspect of the data table is the pool of calculated molecular descriptors. These descriptors provide valuable insights into the molecular characteristics of the compounds under investigation. They aid in understanding the relationship between the compounds' structural properties and their observed retention behavior.

3. Observed response: The observed response parameter consists of retention factors, a fundamental measure in chromatography. These retention factors were measured and recorded during the experimental process. They offer critical information about the compounds' affinity for the stationary phase and their overall behavior in the MLC system.
PB  - University of Belgrade - Faculty of Pharmacy
T2  - Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms
T1  - Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4880
ER  - 

@misc{
author = "Krmar, Jovana",
year = "2023",
abstract = "Data table for model building.

The data table used for modeling includes the following key components:

1. Chromatographic conditions: The chromatographic conditions encompass parameters such as the concentration of Brij L23, the pH of the micellar component of the mobile phase, and the volume fraction of acetonitrile. These parameters are systematically varied within specific ranges according to the experimental plan based on the Box-Behnken design.

2. Calculated molecular descriptors: An important aspect of the data table is the pool of calculated molecular descriptors. These descriptors provide valuable insights into the molecular characteristics of the compounds under investigation. They aid in understanding the relationship between the compounds' structural properties and their observed retention behavior.

3. Observed response: The observed response parameter consists of retention factors, a fundamental measure in chromatography. These retention factors were measured and recorded during the experimental process. They offer critical information about the compounds' affinity for the stationary phase and their overall behavior in the MLC system.",
publisher = "University of Belgrade - Faculty of Pharmacy",
journal = "Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms",
title = "Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4880"
}

Krmar, J.. (2023). Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms. in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms
University of Belgrade - Faculty of Pharmacy..
https://hdl.handle.net/21.15107/rcub_farfar_4880

Krmar J. Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms. in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms. 2023;.
https://hdl.handle.net/21.15107/rcub_farfar_4880 .

Krmar, Jovana, "Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms" in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms (2023),
https://hdl.handle.net/21.15107/rcub_farfar_4880 .

TY  - CHAP
AU  - Krmar, Jovana
AU  - Svrkota, Bojana
AU  - Đajić, Nevena
AU  - Stojanović, Jevrem
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4907
AB  - One-factor-at-a-time experimentation was used for a long time as gold-standard
optimization for liquid chromatographic (LC) method development. This approach
has two downsides as it requires a needlessly great number of experimental runs and it
is unable to identify possible factor interactions. At the end of the last century,
however, this problem could be solved with the introduction of new chemometric
strategies. This chapter aims at presenting quantitative structure–retention relationship
(QSRR) models with structuring possibilities, from the point of feature selection
through various machine learning algorithms that can be used in model building, for
internal and external validation of the proposed models. The presented strategies of
QSRR model can be a good starting point for analysts to use and adopt them as a good
practice for their applications. QSRR models can be used in predicting the retention
behavior of compounds, to point out the molecular features governing the retention,
and consequently to gain insight into the retention mechanisms. In terms of these
applications, special attention was drawn to modified chromatographic systems,
characterized by mobile or stationary phase modifications. Although chromatographic
methods are applied in a wide variety of fields, the greatest attention has been devoted
to the analysis of pharmaceuticals.
PB  - IntechOpen
T2  - Novel Aspects of Gas Chromatography and Chemometrics
T1  - QSRR Approach: Application to Retention Mechanism in Liquid Chromatography
SP  - 113
EP  - 141
DO  - 10.5772/intechopen.106245
ER  - 

@inbook{
author = "Krmar, Jovana and Svrkota, Bojana and Đajić, Nevena and Stojanović, Jevrem and Protić, Ana and Otašević, Biljana",
year = "2023",
abstract = "One-factor-at-a-time experimentation was used for a long time as gold-standard
optimization for liquid chromatographic (LC) method development. This approach
has two downsides as it requires a needlessly great number of experimental runs and it
is unable to identify possible factor interactions. At the end of the last century,
however, this problem could be solved with the introduction of new chemometric
strategies. This chapter aims at presenting quantitative structure–retention relationship
(QSRR) models with structuring possibilities, from the point of feature selection
through various machine learning algorithms that can be used in model building, for
internal and external validation of the proposed models. The presented strategies of
QSRR model can be a good starting point for analysts to use and adopt them as a good
practice for their applications. QSRR models can be used in predicting the retention
behavior of compounds, to point out the molecular features governing the retention,
and consequently to gain insight into the retention mechanisms. In terms of these
applications, special attention was drawn to modified chromatographic systems,
characterized by mobile or stationary phase modifications. Although chromatographic
methods are applied in a wide variety of fields, the greatest attention has been devoted
to the analysis of pharmaceuticals.",
publisher = "IntechOpen",
journal = "Novel Aspects of Gas Chromatography and Chemometrics",
booktitle = "QSRR Approach: Application to Retention Mechanism in Liquid Chromatography",
pages = "113-141",
doi = "10.5772/intechopen.106245"
}

Krmar, J., Svrkota, B., Đajić, N., Stojanović, J., Protić, A.,& Otašević, B.. (2023). QSRR Approach: Application to Retention Mechanism in Liquid Chromatography. in Novel Aspects of Gas Chromatography and Chemometrics
IntechOpen., 113-141.
https://doi.org/10.5772/intechopen.106245

Krmar J, Svrkota B, Đajić N, Stojanović J, Protić A, Otašević B. QSRR Approach: Application to Retention Mechanism in Liquid Chromatography. in Novel Aspects of Gas Chromatography and Chemometrics. 2023;:113-141.
doi:10.5772/intechopen.106245 .

Krmar, Jovana, Svrkota, Bojana, Đajić, Nevena, Stojanović, Jevrem, Protić, Ana, Otašević, Biljana, "QSRR Approach: Application to Retention Mechanism in Liquid Chromatography" in Novel Aspects of Gas Chromatography and Chemometrics (2023):113-141,
https://doi.org/10.5772/intechopen.106245 . .

TY  - JOUR
AU  - Krmar, Jovana
AU  - Tolić Stojadinović, Ljiljana
AU  - Đurkić, Tatjana
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4881
AB  - A priori estimation of analyte response is crucial for the efficient development of liquid chromatography–electrospray ionization/mass spectrometry (LC–ESI/MS) methods, but remains a demanding task given the lack of knowledge about the factors affecting the experimental outcome. In this research, we address the challenge of discovering the interactive relationship between signal response and structural properties, method parameters and solvent-related descriptors throughout an approach featuring quantitative structure–property relationship (QSPR) and design of experiments (DoE). To systematically investigate the experimental domain within which QSPR prediction should be undertaken, we varied LC and instrumental factors according to the Box-Behnken DoE scheme. Seven compounds, including aripiprazole and its impurities, were subjected to 57 different experimental conditions, resulting in 399 LC–ESI/MS data endpoints. To obtain a more standard distribution of the measured response, the peak areas were log-transformed before modeling. QSPR predictions were made using features selected by Genetic Algorithm (GA) and providing Gradient Boosted Trees (GBT) with training data. Proposed model showed satisfactory performance on test data with a RMSEP of 1.57 % and a of 96.48 %. This is the first QSPR study in LC–ESI/MS that provided a holistic overview of the analyte’s response behavior across the experimental and chemical space. Since intramolecular electronic effects and molecular size were given great importance, the GA–GBT model improved the understanding of signal response generation of model compounds. It also highlighted the need to fine-tune the parameters affecting desolvation and droplet charging efficiency.
PB  - Elsevier Inc.
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Predicting liquid chromatography−electrospray ionization/mass spectrometry signal from the structure of model compounds and experimental factors; case study of aripiprazole and its impurities
VL  - 233
DO  - 10.1016/j.jpba.2023.115422
ER  - 

@article{
author = "Krmar, Jovana and Tolić Stojadinović, Ljiljana and Đurkić, Tatjana and Protić, Ana and Otašević, Biljana",
year = "2023",
abstract = "A priori estimation of analyte response is crucial for the efficient development of liquid chromatography–electrospray ionization/mass spectrometry (LC–ESI/MS) methods, but remains a demanding task given the lack of knowledge about the factors affecting the experimental outcome. In this research, we address the challenge of discovering the interactive relationship between signal response and structural properties, method parameters and solvent-related descriptors throughout an approach featuring quantitative structure–property relationship (QSPR) and design of experiments (DoE). To systematically investigate the experimental domain within which QSPR prediction should be undertaken, we varied LC and instrumental factors according to the Box-Behnken DoE scheme. Seven compounds, including aripiprazole and its impurities, were subjected to 57 different experimental conditions, resulting in 399 LC–ESI/MS data endpoints. To obtain a more standard distribution of the measured response, the peak areas were log-transformed before modeling. QSPR predictions were made using features selected by Genetic Algorithm (GA) and providing Gradient Boosted Trees (GBT) with training data. Proposed model showed satisfactory performance on test data with a RMSEP of 1.57 % and a of 96.48 %. This is the first QSPR study in LC–ESI/MS that provided a holistic overview of the analyte’s response behavior across the experimental and chemical space. Since intramolecular electronic effects and molecular size were given great importance, the GA–GBT model improved the understanding of signal response generation of model compounds. It also highlighted the need to fine-tune the parameters affecting desolvation and droplet charging efficiency.",
publisher = "Elsevier Inc.",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Predicting liquid chromatography−electrospray ionization/mass spectrometry signal from the structure of model compounds and experimental factors; case study of aripiprazole and its impurities",
volume = "233",
doi = "10.1016/j.jpba.2023.115422"
}

Krmar, J., Tolić Stojadinović, L., Đurkić, T., Protić, A.,& Otašević, B.. (2023). Predicting liquid chromatography−electrospray ionization/mass spectrometry signal from the structure of model compounds and experimental factors; case study of aripiprazole and its impurities. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Inc.., 233.
https://doi.org/10.1016/j.jpba.2023.115422

Krmar J, Tolić Stojadinović L, Đurkić T, Protić A, Otašević B. Predicting liquid chromatography−electrospray ionization/mass spectrometry signal from the structure of model compounds and experimental factors; case study of aripiprazole and its impurities. in Journal of Pharmaceutical and Biomedical Analysis. 2023;233.
doi:10.1016/j.jpba.2023.115422 .

Krmar, Jovana, Tolić Stojadinović, Ljiljana, Đurkić, Tatjana, Protić, Ana, Otašević, Biljana, "Predicting liquid chromatography−electrospray ionization/mass spectrometry signal from the structure of model compounds and experimental factors; case study of aripiprazole and its impurities" in Journal of Pharmaceutical and Biomedical Analysis, 233 (2023),
https://doi.org/10.1016/j.jpba.2023.115422 . .

TY  - JOUR
AU  - Walther, Rasmus
AU  - Krmar, Jovana
AU  - Leistner, Adrian
AU  - Svrkota, Bojana
AU  - Otašević, Biljana
AU  - Malenović, Anđelija
AU  - Holzgrabe, Ulrike
AU  - Protić, Ana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4698
AB  - An alternative to the time-consuming and error-prone pharmacopoeial gas chromatography method for the analysis of fatty acids (FAs) is urgently needed. The objective was therefore to propose a robust liquid chromatography method with charged aerosol detection for the analysis of polysorbate 80 (PS80) and magnesium stearate. FAs with different numbers of carbon atoms in the chain necessitated the use of a gradient method with a Hypersil Gold C18 column and acetonitrile as organic modifier. The risk-based Analytical Quality by Design approach was applied to define the Method Operable Design Region (MODR). Formic acid concentration, initial and final percentages of acetonitrile, gradient elution time, column temperature, and mobile phase flow rate were identified as critical method parameters (CMPs). The initial and final percentages of acetonitrile were fixed while the remaining CMPs were fine-tuned using response surface methodology. Critical method attributes included the baseline separation of adjacent peaks (α-linolenic and myristic acid, and oleic and petroselinic acid) and the retention factor of the last compound eluted, stearic acid. The MODR was calculated by Monte Carlo simulations with a probability equal or greater than 90%. Finally, the column temperature was set at 33 °C, the flow rate was 0.575 mL/min, and acetonitrile linearly increased from 70 to 80% (v/v) within 14.2 min.
PB  - MDPI
T2  - Pharmaceuticals
T1  - Analytical Quality by Design: Achieving Robustness of an LC-CAD Method for the Analysis of Non-Volatile Fatty Acids
VL  - 16
IS  - 4
DO  - 10.3390/ph16040478
ER  - 

@article{
author = "Walther, Rasmus and Krmar, Jovana and Leistner, Adrian and Svrkota, Bojana and Otašević, Biljana and Malenović, Anđelija and Holzgrabe, Ulrike and Protić, Ana",
year = "2023",
abstract = "An alternative to the time-consuming and error-prone pharmacopoeial gas chromatography method for the analysis of fatty acids (FAs) is urgently needed. The objective was therefore to propose a robust liquid chromatography method with charged aerosol detection for the analysis of polysorbate 80 (PS80) and magnesium stearate. FAs with different numbers of carbon atoms in the chain necessitated the use of a gradient method with a Hypersil Gold C18 column and acetonitrile as organic modifier. The risk-based Analytical Quality by Design approach was applied to define the Method Operable Design Region (MODR). Formic acid concentration, initial and final percentages of acetonitrile, gradient elution time, column temperature, and mobile phase flow rate were identified as critical method parameters (CMPs). The initial and final percentages of acetonitrile were fixed while the remaining CMPs were fine-tuned using response surface methodology. Critical method attributes included the baseline separation of adjacent peaks (α-linolenic and myristic acid, and oleic and petroselinic acid) and the retention factor of the last compound eluted, stearic acid. The MODR was calculated by Monte Carlo simulations with a probability equal or greater than 90%. Finally, the column temperature was set at 33 °C, the flow rate was 0.575 mL/min, and acetonitrile linearly increased from 70 to 80% (v/v) within 14.2 min.",
publisher = "MDPI",
journal = "Pharmaceuticals",
title = "Analytical Quality by Design: Achieving Robustness of an LC-CAD Method for the Analysis of Non-Volatile Fatty Acids",
volume = "16",
number = "4",
doi = "10.3390/ph16040478"
}

Walther, R., Krmar, J., Leistner, A., Svrkota, B., Otašević, B., Malenović, A., Holzgrabe, U.,& Protić, A.. (2023). Analytical Quality by Design: Achieving Robustness of an LC-CAD Method for the Analysis of Non-Volatile Fatty Acids. in Pharmaceuticals
MDPI., 16(4).
https://doi.org/10.3390/ph16040478

Walther R, Krmar J, Leistner A, Svrkota B, Otašević B, Malenović A, Holzgrabe U, Protić A. Analytical Quality by Design: Achieving Robustness of an LC-CAD Method for the Analysis of Non-Volatile Fatty Acids. in Pharmaceuticals. 2023;16(4).
doi:10.3390/ph16040478 .

Walther, Rasmus, Krmar, Jovana, Leistner, Adrian, Svrkota, Bojana, Otašević, Biljana, Malenović, Anđelija, Holzgrabe, Ulrike, Protić, Ana, "Analytical Quality by Design: Achieving Robustness of an LC-CAD Method for the Analysis of Non-Volatile Fatty Acids" in Pharmaceuticals, 16, no. 4 (2023),
https://doi.org/10.3390/ph16040478 . .

TY  - JOUR
AU  - Svrkota, Bojana
AU  - Krmar, Jovana
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4414
AB  - Resolving complex sample mixtures by liquid chromatography in a single run is challenging. The so-called mixed-mode liquid chromatography (MMLC) which combines several retention mechanisms within a single column, can provide resource-efficient separation of solutes of diverse nature. The Acclaim Mixed-Mode WCX-1 column, encompassing hydrophobic and weak cation exchange interactions, was employed for the analysis of small drug molecules. The stationary phase's interaction abilities were assessed by analysing molecules of different ionisation potentials. Mixed Quantitative Structure-Retention Relationship (QSRR) models were developed for revealing significant experimental parameters (EPs) and molecular features governing molecular retention. According to the plan of Face-Centred Central Composite Design, EPs (column temperature, acetonitrile content, pH and buffer concentration of aqueous mobile phase) variations were included in QSRR modelling. QSRRs were developed upon the whole data set (global model) and upon discrete parts, related to similarly ionized analytes (local models) by applying gradient boosted trees as a regression tool. Root mean squared errors of prediction for global and local QSRR models for cations, anions and neutrals were respectively 0.131; 0.105; 0.102 and 0.042 with the coefficient of determination 0.947; 0.872; 0.954 and 0.996, indicating satisfactory performances of all models, with slightly better accuracy of local ones. The research showed that influences of EPs were dependant on the molecule's ionisation potential. The molecular descriptors highlighted by models pointed out that electrostatic and hydrophobic interactions and hydrogen bonds participate in the retention process. The molecule's conformation significance was evaluated along with the topological relationship between the interaction centres, explicitly determined for each molecular species through local models. All models showed good molecular retention predictability thus showing potential for facilitating the method development.
PB  - Elsevier B.V.
T2  - Journal of Chromatography A
T1  - The secret of reversed-phase/weak cation exchange retention mechanisms in mixed-mode liquid chromatography applied for small drug molecule analysis
VL  - 1690
DO  - 10.1016/j.chroma.2023.463776
ER  - 

@article{
author = "Svrkota, Bojana and Krmar, Jovana and Protić, Ana and Otašević, Biljana",
year = "2023",
abstract = "Resolving complex sample mixtures by liquid chromatography in a single run is challenging. The so-called mixed-mode liquid chromatography (MMLC) which combines several retention mechanisms within a single column, can provide resource-efficient separation of solutes of diverse nature. The Acclaim Mixed-Mode WCX-1 column, encompassing hydrophobic and weak cation exchange interactions, was employed for the analysis of small drug molecules. The stationary phase's interaction abilities were assessed by analysing molecules of different ionisation potentials. Mixed Quantitative Structure-Retention Relationship (QSRR) models were developed for revealing significant experimental parameters (EPs) and molecular features governing molecular retention. According to the plan of Face-Centred Central Composite Design, EPs (column temperature, acetonitrile content, pH and buffer concentration of aqueous mobile phase) variations were included in QSRR modelling. QSRRs were developed upon the whole data set (global model) and upon discrete parts, related to similarly ionized analytes (local models) by applying gradient boosted trees as a regression tool. Root mean squared errors of prediction for global and local QSRR models for cations, anions and neutrals were respectively 0.131; 0.105; 0.102 and 0.042 with the coefficient of determination 0.947; 0.872; 0.954 and 0.996, indicating satisfactory performances of all models, with slightly better accuracy of local ones. The research showed that influences of EPs were dependant on the molecule's ionisation potential. The molecular descriptors highlighted by models pointed out that electrostatic and hydrophobic interactions and hydrogen bonds participate in the retention process. The molecule's conformation significance was evaluated along with the topological relationship between the interaction centres, explicitly determined for each molecular species through local models. All models showed good molecular retention predictability thus showing potential for facilitating the method development.",
publisher = "Elsevier B.V.",
journal = "Journal of Chromatography A",
title = "The secret of reversed-phase/weak cation exchange retention mechanisms in mixed-mode liquid chromatography applied for small drug molecule analysis",
volume = "1690",
doi = "10.1016/j.chroma.2023.463776"
}

Svrkota, B., Krmar, J., Protić, A.,& Otašević, B.. (2023). The secret of reversed-phase/weak cation exchange retention mechanisms in mixed-mode liquid chromatography applied for small drug molecule analysis. in Journal of Chromatography A
Elsevier B.V.., 1690.
https://doi.org/10.1016/j.chroma.2023.463776

Svrkota B, Krmar J, Protić A, Otašević B. The secret of reversed-phase/weak cation exchange retention mechanisms in mixed-mode liquid chromatography applied for small drug molecule analysis. in Journal of Chromatography A. 2023;1690.
doi:10.1016/j.chroma.2023.463776 .

Svrkota, Bojana, Krmar, Jovana, Protić, Ana, Otašević, Biljana, "The secret of reversed-phase/weak cation exchange retention mechanisms in mixed-mode liquid chromatography applied for small drug molecule analysis" in Journal of Chromatography A, 1690 (2023),
https://doi.org/10.1016/j.chroma.2023.463776 . .

TY  - DATA
AU  - Krmar, Jovana
PY  - 2023
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4883
AB  - Dataset for mixed QSPR modeling.
The response modeling procedure, which simultaneously considered method parameters, solvent-related descriptors, and structural properties of the analytes, required organizing data into a matrix. The X matrix (Table A.1) refers to the (J × K) LC–ESI(+)/MS data collected for a set of analytes under different working conditions. The total number of rows (J) corresponds to the total number of endpoints (measurements performed). It refers to the number of rows (N) of the Box-Behnken (BBD) experimental matrix that are repeated over C analytes. The rows of the (N x S) BBD matrix show all possible combinations of settings for the factors represented in the columns S. The X matrix comprised a total of K columns, with S columns corresponding to experimental factors, P columns representing solvent-related properties, M columns representing molecular descriptors, and one L column corresponding to response-dependent variable. For the C compounds considered in our study, the molecular descriptors make up a (C x M) Q matrix. Repeated application of the BBD matrix over the C compounds augmented property matrix Q.
PB  - University of Belgrade - Faculty of Pharmacy
T2  - Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms
T1  - Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4883
ER  - 

@misc{
author = "Krmar, Jovana",
year = "2023",
abstract = "Dataset for mixed QSPR modeling.
The response modeling procedure, which simultaneously considered method parameters, solvent-related descriptors, and structural properties of the analytes, required organizing data into a matrix. The X matrix (Table A.1) refers to the (J × K) LC–ESI(+)/MS data collected for a set of analytes under different working conditions. The total number of rows (J) corresponds to the total number of endpoints (measurements performed). It refers to the number of rows (N) of the Box-Behnken (BBD) experimental matrix that are repeated over C analytes. The rows of the (N x S) BBD matrix show all possible combinations of settings for the factors represented in the columns S. The X matrix comprised a total of K columns, with S columns corresponding to experimental factors, P columns representing solvent-related properties, M columns representing molecular descriptors, and one L column corresponding to response-dependent variable. For the C compounds considered in our study, the molecular descriptors make up a (C x M) Q matrix. Repeated application of the BBD matrix over the C compounds augmented property matrix Q.",
publisher = "University of Belgrade - Faculty of Pharmacy",
journal = "Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms",
title = "Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4883"
}

Krmar, J.. (2023). Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms. in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms
University of Belgrade - Faculty of Pharmacy..
https://hdl.handle.net/21.15107/rcub_farfar_4883

Krmar J. Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms. in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms. 2023;.
https://hdl.handle.net/21.15107/rcub_farfar_4883 .

Krmar, Jovana, "Supplementary material for doctoral dissertation: Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms" in Prediction of Retention and Ionization Behavior of Selected Analytes in Micellar Liquid Chromatography and Mass Spectrometry Using Machine Learning Algorithms (2023),
https://hdl.handle.net/21.15107/rcub_farfar_4883 .

TY  - JOUR
AU  - Krmar, Jovana
AU  - Džigal, Merima
AU  - Stojković, Jovana
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4081
AB  - Predicting the response signal in Atmospheric Pressure Chemical Ionization - Mass Spectrometry (APCI-MS) systems appears to be considerably challenging due to a gap in knowledge of governing factors and nature of their relationship with response. In this regard, signal intensity is optimized for each analyte separately through trialand- error approach which impairs the method development and depletes numerous resources. To tackle the given issue, here we proposed the Quantitative Structure - Property Relationship (QSPR) model that estimated the ion signal based on molecular descriptors of tested compounds. In particular, the QSPR model was developed using APCI-MS data acquired for 8 chemical compounds under 41 different experimental conditions. Antipsychotics, namely, sulpiride, risperidone, aripiprazole, bifeprunox, ziprasidone and its three impurities, were selected as model substances to undergo APCI ionization. Experimental (instrumental and solventrelated) parameters were varied according to the scheme of Box-Behnken Design. Gradient Boosted Trees (GBT) technique was used to model sophisticated inputs – output relationships of the monitored system. The GBT algorithm with optimized hyper-parameters (16 estimators, learning rate set to 0.55 and maximal depth set to 7) built a so-called mixed model that yielded satisfactory predictive performance (Root Mean Square Error of Prediction: 5.98%; coefficient of determination: 97.1%). According to the built-in feature selection method, GBT identified experimental factors impacting nebulization and vaporization efficiency, i.e. descriptors related to hydrophobicity and molecular polarizability as the major determinants of observed APCI behavior. Therefore, the proposed model has shed light on the parameters and factors’ interactions that govern the generation of APCI ion signals for the analytes with diverse physical-chemical properties. The established QSPR patterns could be reliably used to predict APCI-MS signal in a variety of experimental environ
PB  - Elsevier B.V.
T2  - Chemometrics and Intelligent Laboratory Systems
T1  - Gradient Boosted Tree model: A fast track tool for predicting the Atmospheric Pressure Chemical Ionization-Mass Spectrometry signal of antipsychotics based on molecular features and experimental settings
VL  - 224
DO  - 10.1016/j.chemolab.2022.104554
ER  - 

@article{
author = "Krmar, Jovana and Džigal, Merima and Stojković, Jovana and Protić, Ana and Otašević, Biljana",
year = "2022",
abstract = "Predicting the response signal in Atmospheric Pressure Chemical Ionization - Mass Spectrometry (APCI-MS) systems appears to be considerably challenging due to a gap in knowledge of governing factors and nature of their relationship with response. In this regard, signal intensity is optimized for each analyte separately through trialand- error approach which impairs the method development and depletes numerous resources. To tackle the given issue, here we proposed the Quantitative Structure - Property Relationship (QSPR) model that estimated the ion signal based on molecular descriptors of tested compounds. In particular, the QSPR model was developed using APCI-MS data acquired for 8 chemical compounds under 41 different experimental conditions. Antipsychotics, namely, sulpiride, risperidone, aripiprazole, bifeprunox, ziprasidone and its three impurities, were selected as model substances to undergo APCI ionization. Experimental (instrumental and solventrelated) parameters were varied according to the scheme of Box-Behnken Design. Gradient Boosted Trees (GBT) technique was used to model sophisticated inputs – output relationships of the monitored system. The GBT algorithm with optimized hyper-parameters (16 estimators, learning rate set to 0.55 and maximal depth set to 7) built a so-called mixed model that yielded satisfactory predictive performance (Root Mean Square Error of Prediction: 5.98%; coefficient of determination: 97.1%). According to the built-in feature selection method, GBT identified experimental factors impacting nebulization and vaporization efficiency, i.e. descriptors related to hydrophobicity and molecular polarizability as the major determinants of observed APCI behavior. Therefore, the proposed model has shed light on the parameters and factors’ interactions that govern the generation of APCI ion signals for the analytes with diverse physical-chemical properties. The established QSPR patterns could be reliably used to predict APCI-MS signal in a variety of experimental environ",
publisher = "Elsevier B.V.",
journal = "Chemometrics and Intelligent Laboratory Systems",
title = "Gradient Boosted Tree model: A fast track tool for predicting the Atmospheric Pressure Chemical Ionization-Mass Spectrometry signal of antipsychotics based on molecular features and experimental settings",
volume = "224",
doi = "10.1016/j.chemolab.2022.104554"
}

Krmar, J., Džigal, M., Stojković, J., Protić, A.,& Otašević, B.. (2022). Gradient Boosted Tree model: A fast track tool for predicting the Atmospheric Pressure Chemical Ionization-Mass Spectrometry signal of antipsychotics based on molecular features and experimental settings. in Chemometrics and Intelligent Laboratory Systems
Elsevier B.V.., 224.
https://doi.org/10.1016/j.chemolab.2022.104554

Krmar J, Džigal M, Stojković J, Protić A, Otašević B. Gradient Boosted Tree model: A fast track tool for predicting the Atmospheric Pressure Chemical Ionization-Mass Spectrometry signal of antipsychotics based on molecular features and experimental settings. in Chemometrics and Intelligent Laboratory Systems. 2022;224.
doi:10.1016/j.chemolab.2022.104554 .

Krmar, Jovana, Džigal, Merima, Stojković, Jovana, Protić, Ana, Otašević, Biljana, "Gradient Boosted Tree model: A fast track tool for predicting the Atmospheric Pressure Chemical Ionization-Mass Spectrometry signal of antipsychotics based on molecular features and experimental settings" in Chemometrics and Intelligent Laboratory Systems, 224 (2022),
https://doi.org/10.1016/j.chemolab.2022.104554 . .

TY  - JOUR
AU  - Đajić, Nevena
AU  - Krmar, Jovana
AU  - Rmandić, Milena
AU  - Rašević, Marija
AU  - Otašević, Biljana
AU  - Zečević, Mira
AU  - Malenović, Anđelija
AU  - Protić, Ana
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4995
AB  - Most commonly used analytical technique for determination of active pharmaceutical ingredients and their impurities in quality control throughout all phases of drug research, development and manufacture is definitely reversed-phase high performance liquid chromatography (RP-HPLC). However, pharmaceutical industry professionals are often faced with various challenges in RP mode, which cannot be resolved with common variations in the composition of the mobile phase. These challenges often occur when analyzing compounds that contain basic ionizable groups, possess large differences in polarities and require consumption of high amounts of toxic organic solvents. Among available strategies for addressing the aforementioned issues, the most convenient one includes RP-HPLC mobile phase modifications by an addition of the proper chemical compounds. In that respect, RP-HPLC method can be easily adapted to the needs of the analysis without time-consuming and expensive equipment procurement. In this review the chaotropic chromatography, micellar liquid chromatography, and cyclodextrin modified RP-HPLC systems are presented and discussed in details. Special attention is devoted to the theoretical background, the possibility of retention modeling and applications in various fields of pharmacy, as well as their prospective in further research.
PB  - Elsevier B.V.
T2  - Journal of Chromatography Open
T1  - Modified aqueous mobile phases: A way to improve retention behavior of active pharmaceutical compounds and their impurities in liquid chromatography
VL  - 2
DO  - 10.1016/j.jcoa.2021.100023
ER  - 

@article{
author = "Đajić, Nevena and Krmar, Jovana and Rmandić, Milena and Rašević, Marija and Otašević, Biljana and Zečević, Mira and Malenović, Anđelija and Protić, Ana",
year = "2022",
abstract = "Most commonly used analytical technique for determination of active pharmaceutical ingredients and their impurities in quality control throughout all phases of drug research, development and manufacture is definitely reversed-phase high performance liquid chromatography (RP-HPLC). However, pharmaceutical industry professionals are often faced with various challenges in RP mode, which cannot be resolved with common variations in the composition of the mobile phase. These challenges often occur when analyzing compounds that contain basic ionizable groups, possess large differences in polarities and require consumption of high amounts of toxic organic solvents. Among available strategies for addressing the aforementioned issues, the most convenient one includes RP-HPLC mobile phase modifications by an addition of the proper chemical compounds. In that respect, RP-HPLC method can be easily adapted to the needs of the analysis without time-consuming and expensive equipment procurement. In this review the chaotropic chromatography, micellar liquid chromatography, and cyclodextrin modified RP-HPLC systems are presented and discussed in details. Special attention is devoted to the theoretical background, the possibility of retention modeling and applications in various fields of pharmacy, as well as their prospective in further research.",
publisher = "Elsevier B.V.",
journal = "Journal of Chromatography Open",
title = "Modified aqueous mobile phases: A way to improve retention behavior of active pharmaceutical compounds and their impurities in liquid chromatography",
volume = "2",
doi = "10.1016/j.jcoa.2021.100023"
}

Đajić, N., Krmar, J., Rmandić, M., Rašević, M., Otašević, B., Zečević, M., Malenović, A.,& Protić, A.. (2022). Modified aqueous mobile phases: A way to improve retention behavior of active pharmaceutical compounds and their impurities in liquid chromatography. in Journal of Chromatography Open
Elsevier B.V.., 2.
https://doi.org/10.1016/j.jcoa.2021.100023

Đajić N, Krmar J, Rmandić M, Rašević M, Otašević B, Zečević M, Malenović A, Protić A. Modified aqueous mobile phases: A way to improve retention behavior of active pharmaceutical compounds and their impurities in liquid chromatography. in Journal of Chromatography Open. 2022;2.
doi:10.1016/j.jcoa.2021.100023 .

Đajić, Nevena, Krmar, Jovana, Rmandić, Milena, Rašević, Marija, Otašević, Biljana, Zečević, Mira, Malenović, Anđelija, Protić, Ana, "Modified aqueous mobile phases: A way to improve retention behavior of active pharmaceutical compounds and their impurities in liquid chromatography" in Journal of Chromatography Open, 2 (2022),
https://doi.org/10.1016/j.jcoa.2021.100023 . .

TY  - CONF
AU  - Protić, Ana
AU  - Milenković, Milan
AU  - Rašević, Marija
AU  - Otašević, Biljana
AU  - Zečević, Mira
AU  - Krmar, Jovana
AU  - Malenović, Anđelija
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4446
AB  - Nowadays, one of the ultimate requirements in drug analysis is rapid method
development, prompt chromatographic run time and long lasting method’s lifecycle. Special
attention should be paid to development of gradient elution (U)HPLC methods that are
commonly related to troubleshooting during the inter-laboratory method transfer. The dwell
volume difference between (U)HPLC systems is the main reason for this issue (1). The aim of
this study was to propose new gradient method development methodology with integrated
dwell volumes values in the optimization process. This is especially useful approach for
industry where is frequently known which (U)HPLC instruments will be applied for drug
analysis. Proposed methodology was tested on the model mixture which encompassed
dabigatran etexilate mesylate and its nine impurities. Experimental design methodology and
three different (U)HPLC instruments with significant dwell volume differences were utilized.
Statistically significant variables were selected with Plackett-Burman design, and along with
dwell volume values were included in D-optimal design. The separation criteria s between
adjacent peaks was selected as output for method optimization. Indirect modelling together
with Monte Carlo simulations enabled selection of optimal and robust chromatographic
conditions joint for all instruments. The optimal conditions included 24% (v/v) of initial
amount of acetonitrile, 54% (v/v) of the final amount of acetonitrile, 15 min of gradient
elution run time and pH value equal to 4.9. The proposed method utility was proved since it
was successfully validated and met all validation criteria (2).
AB  - U današnje vreme, jedan od važnih zahteva prilikom razvoja hromatografskih metoda
jeste da se razvoj uradi brzo, da vreme trajanja hromatografske analize bude kratko i da se
obezbedi dug životni ciklus metode. Posebnu pažnju treba obratiti na (U)HPLC metode sa
gradijentnim eluiranjem kod kojih se često javljaju problemi prilikom međulaboratorijskog
transfera. Glavni razlog za zahtevan transfer gradijentnih (U)HPLC metoda je razlika u
vrednostima dwell volume između (U)HPLC uređaja (1). Cilj ovog rada je bio da predloži
novu metodologiju razvoja gradijentnih (U)HPLC metoda, pri čemu će vrednosti dwell
volumes biti integrisane sa drugim ulaznim promenljivama u fazi optimizacije. Ovo bi bio
posebno koristan pristup u industriji gde se obično zna na kojim će sve (U)HPLC
instrumentima metoda biti korišćena. Metodologija je testirana na smeši dabigatran eteksilat
mezilata i njegovih devet nečistoća. Za razvoj metode korišćen je eksperimentalni dizajn i tri
različita (U)HPLC instrumenta sa značajnim razlikama u dwell volume vrednostima.
Statistički značajne ulazne promenljive su dobijene primenom Plackett‐Burman dizajna, i
zajedno sa vrednostima dwell volume su bile uključene u D‐opimal dizajn. Kriterijum
razdvajanja s između susednih parova pikova odabran je kao odgovor u odnosu na koji je
metoda optimizovana. Indirektno modelovanje zajedno sa Monte Karlo simulacijom
omoguć ilo je izbor optimalnih i robusnih hromatografskih uslova zajedničkih za sva tri
instrumenta. Oni su uključivali 24% (v/v) početnog udela acetonitrila, 54% (v/v) finalnog
udela acetonitrila, vreme trajanja gradijenta od 15 minuta i pH vrednost 4,9. Primenljivost
predložene metodologije je dokazana, jer je dobijena metoda uspešno validirana na sva tri
(U)HPLC instrumenta (2).
PB  - Savez farmaceutskih udruženja Srbije (SFUS)
C3  - Arhiv za farmaciju
T1  - Novel Gradient Elution (U)HPLC Method Development that Enables Successful Method Transfer
T1  - Novi pristup u razvoju (U)HPLC gradijentnih metoda koji bi omogućio uspešan transfer
VL  - 72
IS  - 4 suplement
SP  - S55
EP  - S56
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4446
ER  - 

@conference{
author = "Protić, Ana and Milenković, Milan and Rašević, Marija and Otašević, Biljana and Zečević, Mira and Krmar, Jovana and Malenović, Anđelija",
year = "2022",
abstract = "Nowadays, one of the ultimate requirements in drug analysis is rapid method
development, prompt chromatographic run time and long lasting method’s lifecycle. Special
attention should be paid to development of gradient elution (U)HPLC methods that are
commonly related to troubleshooting during the inter-laboratory method transfer. The dwell
volume difference between (U)HPLC systems is the main reason for this issue (1). The aim of
this study was to propose new gradient method development methodology with integrated
dwell volumes values in the optimization process. This is especially useful approach for
industry where is frequently known which (U)HPLC instruments will be applied for drug
analysis. Proposed methodology was tested on the model mixture which encompassed
dabigatran etexilate mesylate and its nine impurities. Experimental design methodology and
three different (U)HPLC instruments with significant dwell volume differences were utilized.
Statistically significant variables were selected with Plackett-Burman design, and along with
dwell volume values were included in D-optimal design. The separation criteria s between
adjacent peaks was selected as output for method optimization. Indirect modelling together
with Monte Carlo simulations enabled selection of optimal and robust chromatographic
conditions joint for all instruments. The optimal conditions included 24% (v/v) of initial
amount of acetonitrile, 54% (v/v) of the final amount of acetonitrile, 15 min of gradient
elution run time and pH value equal to 4.9. The proposed method utility was proved since it
was successfully validated and met all validation criteria (2)., U današnje vreme, jedan od važnih zahteva prilikom razvoja hromatografskih metoda
jeste da se razvoj uradi brzo, da vreme trajanja hromatografske analize bude kratko i da se
obezbedi dug životni ciklus metode. Posebnu pažnju treba obratiti na (U)HPLC metode sa
gradijentnim eluiranjem kod kojih se često javljaju problemi prilikom međulaboratorijskog
transfera. Glavni razlog za zahtevan transfer gradijentnih (U)HPLC metoda je razlika u
vrednostima dwell volume između (U)HPLC uređaja (1). Cilj ovog rada je bio da predloži
novu metodologiju razvoja gradijentnih (U)HPLC metoda, pri čemu će vrednosti dwell
volumes biti integrisane sa drugim ulaznim promenljivama u fazi optimizacije. Ovo bi bio
posebno koristan pristup u industriji gde se obično zna na kojim će sve (U)HPLC
instrumentima metoda biti korišćena. Metodologija je testirana na smeši dabigatran eteksilat
mezilata i njegovih devet nečistoća. Za razvoj metode korišćen je eksperimentalni dizajn i tri
različita (U)HPLC instrumenta sa značajnim razlikama u dwell volume vrednostima.
Statistički značajne ulazne promenljive su dobijene primenom Plackett‐Burman dizajna, i
zajedno sa vrednostima dwell volume su bile uključene u D‐opimal dizajn. Kriterijum
razdvajanja s između susednih parova pikova odabran je kao odgovor u odnosu na koji je
metoda optimizovana. Indirektno modelovanje zajedno sa Monte Karlo simulacijom
omoguć ilo je izbor optimalnih i robusnih hromatografskih uslova zajedničkih za sva tri
instrumenta. Oni su uključivali 24% (v/v) početnog udela acetonitrila, 54% (v/v) finalnog
udela acetonitrila, vreme trajanja gradijenta od 15 minuta i pH vrednost 4,9. Primenljivost
predložene metodologije je dokazana, jer je dobijena metoda uspešno validirana na sva tri
(U)HPLC instrumenta (2).",
publisher = "Savez farmaceutskih udruženja Srbije (SFUS)",
journal = "Arhiv za farmaciju",
title = "Novel Gradient Elution (U)HPLC Method Development that Enables Successful Method Transfer, Novi pristup u razvoju (U)HPLC gradijentnih metoda koji bi omogućio uspešan transfer",
volume = "72",
number = "4 suplement",
pages = "S55-S56",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4446"
}

Protić, A., Milenković, M., Rašević, M., Otašević, B., Zečević, M., Krmar, J.,& Malenović, A.. (2022). Novel Gradient Elution (U)HPLC Method Development that Enables Successful Method Transfer. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije (SFUS)., 72(4 suplement), S55-S56.
https://hdl.handle.net/21.15107/rcub_farfar_4446

Protić A, Milenković M, Rašević M, Otašević B, Zečević M, Krmar J, Malenović A. Novel Gradient Elution (U)HPLC Method Development that Enables Successful Method Transfer. in Arhiv za farmaciju. 2022;72(4 suplement):S55-S56.
https://hdl.handle.net/21.15107/rcub_farfar_4446 .

Protić, Ana, Milenković, Milan, Rašević, Marija, Otašević, Biljana, Zečević, Mira, Krmar, Jovana, Malenović, Anđelija, "Novel Gradient Elution (U)HPLC Method Development that Enables Successful Method Transfer" in Arhiv za farmaciju, 72, no. 4 suplement (2022):S55-S56,
https://hdl.handle.net/21.15107/rcub_farfar_4446 .

TY  - CONF
AU  - Svrkota, Bojana
AU  - Krmar, Jovana
AU  - Đajić, Nevena
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4692
AB  - Introduction: Active pharmaceutical ingredients
(APIs) are often used in salt form, which is why the
inclusion of weak cation exchange (WCX), in
addition to reverse-phased (RP) hydrophobic
interactions, could improve APIs’ separation (1).
Due to the limited knowledge about the RP/WCX
bimodal system, the aim was to elucidate the
experimental factors’ influence on the retention of
diverse ionized APIs, and provide efficient method
optimization.
Materials and Methods: Acidic (ibuprofen (IB),
aceclofenac (AC)) and basic (escitalopram (ES),
aripiprazole (AR), atomoxetine (AT)) analytes were
tested. Chromatography experiments were
performed on Thermo Acclaim Mixed Mode WCX-
1 (5 μm, 3x10 mm) column. Mobile phase
consisted of ACN (30-50% (v/v)) and acetic buffer
(pH 3.8 - 5.6; ionic strength (I) 20-40 mM).
Temperature (T) was varied in range 30–38 °C.
Variations of these factors were conducted
according to Full Factorial Design 24. Optimization
phase was executed by using face-centered
Central Composite Design (Design-Expert 7.0.0).
Results: Screening results showed that %ACN
had the greatest impact on analytes’ retention
factors (k), so increasing in %ACN caused a
decrease in k. T had the same effect, but much less
pronounced. Changes in mobile phase pH affected
k, with the opposite effect on anionic and cationic species. This is attributed to greater ionization of
stationary phases’ carboxylic groups at higher pH.
As consequence, repulsive interactions with
anionic and attractive interactions with the cationic
analytes, are enhanced, vice versa (2). Ionic
strength had much more influence on cationic
analytes than on anionic ones. Due to all the
above, all of four factors were included during
optimization phase. Optimization goals were set so
that k values were in range 1–10 (k(AR)<10,
k(AC)>10, k(IB) in range) and selectivity of critical
peak pair α(AT/ES)>1.3. All derived mathematical
models were statistically estimated (R2, adj. R2,
pred. R2>0.95). Set of optimal conditions which is
47% (v/v) ACN, acetic buffer (40 mМ, pH 3.8) and
temperature 30 °C was determined using
Derringer’s desirability function.
Conclusions: Experimental parameters with
significant influence on retention in bimodal
RP/WCX system were evaluated, and upon that
method was successfully optimized.
PB  - Ankara University Faculty of Pharmacy
C3  - 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey
T1  - Chemometrically supported optimization of RP/WCX-HPLC method
SP  - 228
EP  - 229
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4692
ER  - 

@conference{
author = "Svrkota, Bojana and Krmar, Jovana and Đajić, Nevena and Protić, Ana and Otašević, Biljana",
year = "2022",
abstract = "Introduction: Active pharmaceutical ingredients
(APIs) are often used in salt form, which is why the
inclusion of weak cation exchange (WCX), in
addition to reverse-phased (RP) hydrophobic
interactions, could improve APIs’ separation (1).
Due to the limited knowledge about the RP/WCX
bimodal system, the aim was to elucidate the
experimental factors’ influence on the retention of
diverse ionized APIs, and provide efficient method
optimization.
Materials and Methods: Acidic (ibuprofen (IB),
aceclofenac (AC)) and basic (escitalopram (ES),
aripiprazole (AR), atomoxetine (AT)) analytes were
tested. Chromatography experiments were
performed on Thermo Acclaim Mixed Mode WCX-
1 (5 μm, 3x10 mm) column. Mobile phase
consisted of ACN (30-50% (v/v)) and acetic buffer
(pH 3.8 - 5.6; ionic strength (I) 20-40 mM).
Temperature (T) was varied in range 30–38 °C.
Variations of these factors were conducted
according to Full Factorial Design 24. Optimization
phase was executed by using face-centered
Central Composite Design (Design-Expert 7.0.0).
Results: Screening results showed that %ACN
had the greatest impact on analytes’ retention
factors (k), so increasing in %ACN caused a
decrease in k. T had the same effect, but much less
pronounced. Changes in mobile phase pH affected
k, with the opposite effect on anionic and cationic species. This is attributed to greater ionization of
stationary phases’ carboxylic groups at higher pH.
As consequence, repulsive interactions with
anionic and attractive interactions with the cationic
analytes, are enhanced, vice versa (2). Ionic
strength had much more influence on cationic
analytes than on anionic ones. Due to all the
above, all of four factors were included during
optimization phase. Optimization goals were set so
that k values were in range 1–10 (k(AR)<10,
k(AC)>10, k(IB) in range) and selectivity of critical
peak pair α(AT/ES)>1.3. All derived mathematical
models were statistically estimated (R2, adj. R2,
pred. R2>0.95). Set of optimal conditions which is
47% (v/v) ACN, acetic buffer (40 mМ, pH 3.8) and
temperature 30 °C was determined using
Derringer’s desirability function.
Conclusions: Experimental parameters with
significant influence on retention in bimodal
RP/WCX system were evaluated, and upon that
method was successfully optimized.",
publisher = "Ankara University Faculty of Pharmacy",
journal = "13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey",
title = "Chemometrically supported optimization of RP/WCX-HPLC method",
pages = "228-229",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4692"
}

Svrkota, B., Krmar, J., Đajić, N., Protić, A.,& Otašević, B.. (2022). Chemometrically supported optimization of RP/WCX-HPLC method. in 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey
Ankara University Faculty of Pharmacy., 228-229.
https://hdl.handle.net/21.15107/rcub_farfar_4692

Svrkota B, Krmar J, Đajić N, Protić A, Otašević B. Chemometrically supported optimization of RP/WCX-HPLC method. in 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey. 2022;:228-229.
https://hdl.handle.net/21.15107/rcub_farfar_4692 .

Svrkota, Bojana, Krmar, Jovana, Đajić, Nevena, Protić, Ana, Otašević, Biljana, "Chemometrically supported optimization of RP/WCX-HPLC method" in 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey (2022):228-229,
https://hdl.handle.net/21.15107/rcub_farfar_4692 .

TY  - CONF
AU  - Krmar, Jovana
AU  - Tolić-Stojadinović, Ljiljana
AU  - Vukićević, Milan
AU  - Đurkić, Tatjana
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4691
PB  - University of Mons (Belgium)
C3  - 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book
T1  - The modern age of chemomometrics: What is the secret behind LC–ESI(+)/MS response generation?
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4691
ER  - 

@conference{
author = "Krmar, Jovana and Tolić-Stojadinović, Ljiljana and Vukićević, Milan and Đurkić, Tatjana and Protić, Ana and Otašević, Biljana",
year = "2022",
publisher = "University of Mons (Belgium)",
journal = "12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book",
title = "The modern age of chemomometrics: What is the secret behind LC–ESI(+)/MS response generation?",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4691"
}

Krmar, J., Tolić-Stojadinović, L., Vukićević, M., Đurkić, T., Protić, A.,& Otašević, B.. (2022). The modern age of chemomometrics: What is the secret behind LC–ESI(+)/MS response generation?. in 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book
University of Mons (Belgium)..
https://hdl.handle.net/21.15107/rcub_farfar_4691

Krmar J, Tolić-Stojadinović L, Vukićević M, Đurkić T, Protić A, Otašević B. The modern age of chemomometrics: What is the secret behind LC–ESI(+)/MS response generation?. in 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book. 2022;.
https://hdl.handle.net/21.15107/rcub_farfar_4691 .

Krmar, Jovana, Tolić-Stojadinović, Ljiljana, Vukićević, Milan, Đurkić, Tatjana, Protić, Ana, Otašević, Biljana, "The modern age of chemomometrics: What is the secret behind LC–ESI(+)/MS response generation?" in 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book (2022),
https://hdl.handle.net/21.15107/rcub_farfar_4691 .

TY  - CONF
AU  - Svrkota, Bojana
AU  - Krmar, Jovana
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4689
PB  - University of Mons (Belgium)
C3  - 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book
T1  - Mixed-mode RP/WCX chromatographic system evaluation using QSRR modelling approach
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4689
ER  - 

@conference{
author = "Svrkota, Bojana and Krmar, Jovana and Protić, Ana and Otašević, Biljana",
year = "2022",
publisher = "University of Mons (Belgium)",
journal = "12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book",
title = "Mixed-mode RP/WCX chromatographic system evaluation using QSRR modelling approach",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4689"
}

Svrkota, B., Krmar, J., Protić, A.,& Otašević, B.. (2022). Mixed-mode RP/WCX chromatographic system evaluation using QSRR modelling approach. in 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book
University of Mons (Belgium)..
https://hdl.handle.net/21.15107/rcub_farfar_4689

Svrkota B, Krmar J, Protić A, Otašević B. Mixed-mode RP/WCX chromatographic system evaluation using QSRR modelling approach. in 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book. 2022;.
https://hdl.handle.net/21.15107/rcub_farfar_4689 .

Svrkota, Bojana, Krmar, Jovana, Protić, Ana, Otašević, Biljana, "Mixed-mode RP/WCX chromatographic system evaluation using QSRR modelling approach" in 12th International Symposium on Drug Analysis & 32nd International Symposium on Pharmaceutical and Biomedical Analysis, From 11th to 14th September 2022, Mons, Belgium, Abstract book (2022),
https://hdl.handle.net/21.15107/rcub_farfar_4689 .

TY  - CONF
AU  - Otašević, Biljana
AU  - Svrkota, Bojana
AU  - Krmar, Jovana
AU  - Protić, Ana
AU  - Zečević, Mira
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4688
AB  - Liquid chromatography which implies that an analyte interacts through several
separation mechanisms (modes) with a stationary phase packed in a single chromatographic
column is called multimodal or mixed-mode chromatography (MMC). Based on the combined
modes, MMC is seen as bimodal (RP/HILIC, RP/IEX, HILIC/IEX) or trimodal (different
RP/HILIC/IEXcombinations) system. Consequently, compounds that encompass wide
spectra of properties (nonpolar, polar, organic, inorganic, ionized and/or non-ionized) can
be chromatographed in a single chromatographic run. The main practical achievement of this
is the reduction of the number of required analyses needed per one complex sample
compared to unimodal chromatographic systems. Therefore, the popularity of MMC grows
rapidly in recent years together with the number of its applications (1). Beside common
quality control issues that include active pharmaceutical ingredients and related substances
analysis and impurity profiling, the range of different analytes which MMC successfully
handles extends to the analyses of drugs in environmental and biological samples, peptides
and proteins. Since nearly half of recently FDA approved pharmaceutical substances are in
the form of a salt, the focus of MMC turned to pharmaceutical counterions analyses as well
(2). However, separations are governed by numerous intermolecular interactions resulting
from specific analyteʼs properties (size, charge, polarity) and mobile phase composition
(aqueous phase ionic strength and pH value, organic solvent content) while the quality of
separation can also be affected by column temperature and mobile phase flow rate.
Eventually, analytical method development is challenging and demands the assistance of
multifactorial optimization strategies such as the design of experiments.
AB  - Tečna hromatografija koja podrazumeva da analit interaguje putem nekoliko
mehanizama razdvajanja (modova) sa stacionarnom fazom upakovanom u jednu istu
hromatografsku kolonu naziva se multimodalna hromatografija (MMC). Na osnovu
kombinovanih modova, MMC se posmatra kao bimodalni (RP/HILIC, RP/IEX, HILIC/IEX) ili
trimodalni (različite RP/HILIC/IEX kombinacije) sistem. Ovo za posledicu ima da jedinjenja
širokog spektra svojstava (nepolarna, polarna, organska, neorganska, jonizovana i/ili
nejonizovana) mogu se hromatografisati u jednom ciklusu hromatografije. Glavni praktični
doprinos ovoga je smanjenje broja potrebnih analiza po jednom složenom uzorku u
poređenju sa unimodalnim hromatografskim sistemima. Zbog toga, popularnost MMC naglo
raste poslednjih godina zajedno sa brojem njenih aplikacija (1). Pored uobičajenih pitanja
kontrole kvaliteta koja uključuju analizu aktivnih farmaceutskih sastojaka i srodnih
supstanci i profilisanje nečistoća, opseg različitih analita sa kojima MMC uspešno pokriva
proširen je analitikom lekova iz prirodnog okruženja i bioloških uzoraka, peptidima i
proteinima. Pošto je skoro polovina farmaceutskih supstanci koje je nedavno FDA odobrila u
obliku soli, fokus MMC je orjentisan i ka analizi farmaceutskih kontrajona (2). Međutim,
hromatografsko razdvajanje je vođeno brojnim intermolekularnim interakcijima koje su
rezultat specifičnih svojstava analita (veličina, naelektrisanje, polaritet) i mobilne faze
(jonska jačina i pH vrednost vodene faze, sadržaj organskog rastvarača), dok na kvalitet
razdvajanja može uticati i temperatura kolone i brzina protoka mobilne faze. Na kraju, razvoj
analitičkih metoda predstavlja izazov i zahteva podršku u strategijama multifaktorske
optimizacije kao što je dizajn eksperimenata.
PB  - Savez farmaceutskih udruženja Srbije (SFUS)
C3  - Arhiv za farmaciju
T1  - The use of multimodal chromatography in the control of pharmaceutical products: New possibilities and new challenges
T1  - Primena multimodalne hromatografije u kontroli farmaceutskih proizvoda: Nove mogućnosti i novi izazovi
VL  - 72
IS  - suppl. 4
SP  - 57
EP  - 58
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4688
ER  - 

@conference{
author = "Otašević, Biljana and Svrkota, Bojana and Krmar, Jovana and Protić, Ana and Zečević, Mira",
year = "2022",
abstract = "Liquid chromatography which implies that an analyte interacts through several
separation mechanisms (modes) with a stationary phase packed in a single chromatographic
column is called multimodal or mixed-mode chromatography (MMC). Based on the combined
modes, MMC is seen as bimodal (RP/HILIC, RP/IEX, HILIC/IEX) or trimodal (different
RP/HILIC/IEXcombinations) system. Consequently, compounds that encompass wide
spectra of properties (nonpolar, polar, organic, inorganic, ionized and/or non-ionized) can
be chromatographed in a single chromatographic run. The main practical achievement of this
is the reduction of the number of required analyses needed per one complex sample
compared to unimodal chromatographic systems. Therefore, the popularity of MMC grows
rapidly in recent years together with the number of its applications (1). Beside common
quality control issues that include active pharmaceutical ingredients and related substances
analysis and impurity profiling, the range of different analytes which MMC successfully
handles extends to the analyses of drugs in environmental and biological samples, peptides
and proteins. Since nearly half of recently FDA approved pharmaceutical substances are in
the form of a salt, the focus of MMC turned to pharmaceutical counterions analyses as well
(2). However, separations are governed by numerous intermolecular interactions resulting
from specific analyteʼs properties (size, charge, polarity) and mobile phase composition
(aqueous phase ionic strength and pH value, organic solvent content) while the quality of
separation can also be affected by column temperature and mobile phase flow rate.
Eventually, analytical method development is challenging and demands the assistance of
multifactorial optimization strategies such as the design of experiments., Tečna hromatografija koja podrazumeva da analit interaguje putem nekoliko
mehanizama razdvajanja (modova) sa stacionarnom fazom upakovanom u jednu istu
hromatografsku kolonu naziva se multimodalna hromatografija (MMC). Na osnovu
kombinovanih modova, MMC se posmatra kao bimodalni (RP/HILIC, RP/IEX, HILIC/IEX) ili
trimodalni (različite RP/HILIC/IEX kombinacije) sistem. Ovo za posledicu ima da jedinjenja
širokog spektra svojstava (nepolarna, polarna, organska, neorganska, jonizovana i/ili
nejonizovana) mogu se hromatografisati u jednom ciklusu hromatografije. Glavni praktični
doprinos ovoga je smanjenje broja potrebnih analiza po jednom složenom uzorku u
poređenju sa unimodalnim hromatografskim sistemima. Zbog toga, popularnost MMC naglo
raste poslednjih godina zajedno sa brojem njenih aplikacija (1). Pored uobičajenih pitanja
kontrole kvaliteta koja uključuju analizu aktivnih farmaceutskih sastojaka i srodnih
supstanci i profilisanje nečistoća, opseg različitih analita sa kojima MMC uspešno pokriva
proširen je analitikom lekova iz prirodnog okruženja i bioloških uzoraka, peptidima i
proteinima. Pošto je skoro polovina farmaceutskih supstanci koje je nedavno FDA odobrila u
obliku soli, fokus MMC je orjentisan i ka analizi farmaceutskih kontrajona (2). Međutim,
hromatografsko razdvajanje je vođeno brojnim intermolekularnim interakcijima koje su
rezultat specifičnih svojstava analita (veličina, naelektrisanje, polaritet) i mobilne faze
(jonska jačina i pH vrednost vodene faze, sadržaj organskog rastvarača), dok na kvalitet
razdvajanja može uticati i temperatura kolone i brzina protoka mobilne faze. Na kraju, razvoj
analitičkih metoda predstavlja izazov i zahteva podršku u strategijama multifaktorske
optimizacije kao što je dizajn eksperimenata.",
publisher = "Savez farmaceutskih udruženja Srbije (SFUS)",
journal = "Arhiv za farmaciju",
title = "The use of multimodal chromatography in the control of pharmaceutical products: New possibilities and new challenges, Primena multimodalne hromatografije u kontroli farmaceutskih proizvoda: Nove mogućnosti i novi izazovi",
volume = "72",
number = "suppl. 4",
pages = "57-58",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4688"
}

Otašević, B., Svrkota, B., Krmar, J., Protić, A.,& Zečević, M.. (2022). The use of multimodal chromatography in the control of pharmaceutical products: New possibilities and new challenges. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije (SFUS)., 72(suppl. 4), 57-58.
https://hdl.handle.net/21.15107/rcub_farfar_4688

Otašević B, Svrkota B, Krmar J, Protić A, Zečević M. The use of multimodal chromatography in the control of pharmaceutical products: New possibilities and new challenges. in Arhiv za farmaciju. 2022;72(suppl. 4):57-58.
https://hdl.handle.net/21.15107/rcub_farfar_4688 .

Otašević, Biljana, Svrkota, Bojana, Krmar, Jovana, Protić, Ana, Zečević, Mira, "The use of multimodal chromatography in the control of pharmaceutical products: New possibilities and new challenges" in Arhiv za farmaciju, 72, no. suppl. 4 (2022):57-58,
https://hdl.handle.net/21.15107/rcub_farfar_4688 .

TY  - CONF
AU  - Svrkota, Bojana
AU  - Krmar, Jovana
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4524
AB  - Mixed-Mode Liquid Chromatography (MMLC) includes several separation
mechanisms in a single column, which is why MMLC can analyze compounds in a broad
range of polarities and ionization potentials in a single run (1). Acclaim Mixed-Mode WCX-1
column with the ability to expose hydrophobic and weak cation exchange interactions was
thus selected to analyse a challenging mixture of neutral and cationic forms: ergotamine,
mecloxamine, camylofin, caffeine and propyphenazone, used as a fixed combination. MMLC
method was developed in line with Analytical Quality by Design (AQbD) approach implying
the scientifically-based understanding of process properties and risk-based management of
the method life cycle. AQbD refers to pre-definition of the method’s Analytical Target Profile
(ATP) by means of baseline separations within the shortest possible time, as well as
definition of Critical Method Attributes (CMAs) as a measure of method quality and Critical
Method Parameters (CMPs) affecting CMAs (2). Acetonitrile content, pH and acetate buffer
concentration were selected as CMPs since retention mechanism expression in MMLC
strongly depends on the mobile phase characteristics. The dependence of CMAs on CMPs was
revealed following a face-centred central composition design plan of experiments and
accompanying mathematical models, coefficients and standard error values. Design Space in
which ATP is achieved with a high level of reliability (π = 90%), was determined by Monte
Carlo simulations taking error distribution into account. Its margins pointed out to the
working point that assures proper method robustness (pH 5.2, 90 mM acetate buffer solution
and 48% (v/v) of acetonitrile).
AB  - Multimodalna tečna hromatografija (Mixed‐Mode Liquid Chromatography – MMLC)
uključuje nekoliko mehanizama razdvajanja u jednoj koloni, zbog čega se ova tehnika može
koristiti za simultanu analizu jedinjenja širokog opsega polarnosti i jonizacionog potencijala
(1). Acclaim Mixed‐Mode WCX‐1 kolona sa sposobnošću ekspresije hidrofobnih i interakcija
slabe katjonske izmene, je odabrana za analizu izazovne smeše neutralnih i katjonskih oblika
analita: ergotamina, mekloksamina, kamilofina, kofeina i propifenazona, koji se primenjuju u
fiksnoj kombinaciji. MMLC metoda je razvijena u skladu sa pristupom ugradnje kvaliteta kroz
dizajn (Analytical Quality by Design – AQbD) koji podrazumeva naučno zasnovano
razumevanje svojstava procesa i upravljanje životnim ciklusom metode prema riziku. AQbD
se odnosi na unapred definisanje analitičkog ciljanog profila metode (Analytical Target
Profile - ATP) odnosno razdvajanje na baznoj liniji za što kraće vreme, kao i na definisanje
kritičnih osobina metode (Critical Method Attributes - CMA) kao mere kvaliteta metode i
kritičnih parametara metode (Critical Method Parameters - CMP) koji utiču na CMA (2).
Sadržaj acetonitrila, pH i koncentracija acetatnog pufera izabrani su kao CMP, pošto
ekspresija MMLC retencionih mehanizma zavisi od karakteristika mobilne faze. Zavisnost
CMA od CMP definisana je pomoću plana eksperimenata usklađenim sa centralnim
kompozicionim dizajnom, ka centru orijentisanim i pratećim matematičkim modelima,
koeficijentima i vrednostima standardne greške. Prostor dizajna u kome se ATP postiže sa
visokim nivoom pouzdanosti (π = 90%) određen je Monte Karlo simulacijama uzimajuć i u
obzir distribuciju grešaka. Njegov okvir ukazuje na radnu tačku koja obezbeđuje
odgovarajuć u robusnost metode (pH 5,2, 90 mM rastvor acetatnog pufera i 48% (v/v)
acetonitrila).
PB  - Savez farmaceutskih udruženja Srbije (SFUS)
C3  - Arhiv za farmaciju
T1  - Robust mixed-mode chromatography method development using Analytical Quality by Design approach for analysis of selected drugs
T1  - Robustan razvoj metode multimodalne hromatografije primenom principa ugrađivanja kvaliteta kroz dizajn za analizu odabarnih lekova
VL  - 72
IS  - 4 suplement
SP  - S243
EP  - S244
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4524
ER  - 

@conference{
author = "Svrkota, Bojana and Krmar, Jovana and Protić, Ana and Otašević, Biljana",
year = "2022",
abstract = "Mixed-Mode Liquid Chromatography (MMLC) includes several separation
mechanisms in a single column, which is why MMLC can analyze compounds in a broad
range of polarities and ionization potentials in a single run (1). Acclaim Mixed-Mode WCX-1
column with the ability to expose hydrophobic and weak cation exchange interactions was
thus selected to analyse a challenging mixture of neutral and cationic forms: ergotamine,
mecloxamine, camylofin, caffeine and propyphenazone, used as a fixed combination. MMLC
method was developed in line with Analytical Quality by Design (AQbD) approach implying
the scientifically-based understanding of process properties and risk-based management of
the method life cycle. AQbD refers to pre-definition of the method’s Analytical Target Profile
(ATP) by means of baseline separations within the shortest possible time, as well as
definition of Critical Method Attributes (CMAs) as a measure of method quality and Critical
Method Parameters (CMPs) affecting CMAs (2). Acetonitrile content, pH and acetate buffer
concentration were selected as CMPs since retention mechanism expression in MMLC
strongly depends on the mobile phase characteristics. The dependence of CMAs on CMPs was
revealed following a face-centred central composition design plan of experiments and
accompanying mathematical models, coefficients and standard error values. Design Space in
which ATP is achieved with a high level of reliability (π = 90%), was determined by Monte
Carlo simulations taking error distribution into account. Its margins pointed out to the
working point that assures proper method robustness (pH 5.2, 90 mM acetate buffer solution
and 48% (v/v) of acetonitrile)., Multimodalna tečna hromatografija (Mixed‐Mode Liquid Chromatography – MMLC)
uključuje nekoliko mehanizama razdvajanja u jednoj koloni, zbog čega se ova tehnika može
koristiti za simultanu analizu jedinjenja širokog opsega polarnosti i jonizacionog potencijala
(1). Acclaim Mixed‐Mode WCX‐1 kolona sa sposobnošću ekspresije hidrofobnih i interakcija
slabe katjonske izmene, je odabrana za analizu izazovne smeše neutralnih i katjonskih oblika
analita: ergotamina, mekloksamina, kamilofina, kofeina i propifenazona, koji se primenjuju u
fiksnoj kombinaciji. MMLC metoda je razvijena u skladu sa pristupom ugradnje kvaliteta kroz
dizajn (Analytical Quality by Design – AQbD) koji podrazumeva naučno zasnovano
razumevanje svojstava procesa i upravljanje životnim ciklusom metode prema riziku. AQbD
se odnosi na unapred definisanje analitičkog ciljanog profila metode (Analytical Target
Profile - ATP) odnosno razdvajanje na baznoj liniji za što kraće vreme, kao i na definisanje
kritičnih osobina metode (Critical Method Attributes - CMA) kao mere kvaliteta metode i
kritičnih parametara metode (Critical Method Parameters - CMP) koji utiču na CMA (2).
Sadržaj acetonitrila, pH i koncentracija acetatnog pufera izabrani su kao CMP, pošto
ekspresija MMLC retencionih mehanizma zavisi od karakteristika mobilne faze. Zavisnost
CMA od CMP definisana je pomoću plana eksperimenata usklađenim sa centralnim
kompozicionim dizajnom, ka centru orijentisanim i pratećim matematičkim modelima,
koeficijentima i vrednostima standardne greške. Prostor dizajna u kome se ATP postiže sa
visokim nivoom pouzdanosti (π = 90%) određen je Monte Karlo simulacijama uzimajuć i u
obzir distribuciju grešaka. Njegov okvir ukazuje na radnu tačku koja obezbeđuje
odgovarajuć u robusnost metode (pH 5,2, 90 mM rastvor acetatnog pufera i 48% (v/v)
acetonitrila).",
publisher = "Savez farmaceutskih udruženja Srbije (SFUS)",
journal = "Arhiv za farmaciju",
title = "Robust mixed-mode chromatography method development using Analytical Quality by Design approach for analysis of selected drugs, Robustan razvoj metode multimodalne hromatografije primenom principa ugrađivanja kvaliteta kroz dizajn za analizu odabarnih lekova",
volume = "72",
number = "4 suplement",
pages = "S243-S244",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4524"
}

Svrkota, B., Krmar, J., Protić, A.,& Otašević, B.. (2022). Robust mixed-mode chromatography method development using Analytical Quality by Design approach for analysis of selected drugs. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije (SFUS)., 72(4 suplement), S243-S244.
https://hdl.handle.net/21.15107/rcub_farfar_4524

Svrkota B, Krmar J, Protić A, Otašević B. Robust mixed-mode chromatography method development using Analytical Quality by Design approach for analysis of selected drugs. in Arhiv za farmaciju. 2022;72(4 suplement):S243-S244.
https://hdl.handle.net/21.15107/rcub_farfar_4524 .

Svrkota, Bojana, Krmar, Jovana, Protić, Ana, Otašević, Biljana, "Robust mixed-mode chromatography method development using Analytical Quality by Design approach for analysis of selected drugs" in Arhiv za farmaciju, 72, no. 4 suplement (2022):S243-S244,
https://hdl.handle.net/21.15107/rcub_farfar_4524 .

TY  - JOUR
AU  - Svrkota, Bojana
AU  - Krmar, Jovana
AU  - Protić, Ana
AU  - Zečević, Mira
AU  - Otašević, Biljana
PY  - 2022
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4330
AB  - A new optimization strategy based on the mixed quantitative struc- ture–retention relationship (QSRR) model is proposed for improving the RP- HPLC separation of aripiprazole and its impurities (IMP A-E). Firstly, experi- mental parameters (EPs), namely mobile phase composition and flow rate, were varied according to Box–Behnken design and thereafter, an artificial neural network (ANN) as a QSRR model was built correlating EPs and sel- ected molecular descriptors (ovality, torsion energy and non-1,4-van der Waals energy) with the log-transformed retention times of the analytes. Values of the root mean square error (RMSE) were used for an estimation of the quality of the ANNs (0.0227, 0.0191 and 0.0230 for the training, verification and test set, respectively). The separations of critical peak pairs on chromatogram (IMP A- B and IMP D-C) were optimized using ANNs for which the EPs served as inputs and the log-transformed separation criteria s as the outputs. They were validated by application of leave-one-out cross-validation (RMSE values 0.065 and 0.056, respectively). The obtained ANNs were used for plotting response surfaces upon which the analyses chromatographic conditions resulting in optimal analytes retention behaviour and the optimal values of the separation criteria s were defined. The optimal conditions were 54 % of methanol at the beginning and 79 % of methanol at the end of gradient elution programme with a mobile phase flow rate of 460 μL min-1
AB  - Нова оптимизациона стратегија заснована на грађењу мешовитих модела за кван- тификовање односа структуре и ретенционог понашања (QSRR) предложена је за уна- пређење RP-HPLC раздвајања арипипразола и његових нечистоћа (IMP А-Е). Експери- ментални параметри (EP), састав мобилне фазе и брзина протока, варирани су најпре у складу са Box–Behnken дизајном, а затим је награђена вештачка неуронска мрежа као QSRR модел који повезује ЕP и одабране молекуларне дескрипторе (овалност, торзиона енергија и не-1,4-ван дер Валсова енергија) са логаритамски трансформисаним ретен- ционим временом аналита. Вредности средње квадратне грешке (RMSE) коришћене су за процену квалитета мреже (0,0227, 0,0191 и 0,0230 за тренинг, верификацију и тест сет, редом). Раздвајање критичних парова пикова на хроматограму (IMP А-B и IMP D-C) оптимизовано је коришћењем мрежа за које су ЕP послужили као улази, а логаритамски трансформисани критеријуми сепарације s као излази. Ове мреже су валидиране при- меном унакрсне валидације изостанка (RMSE вредности, редом, 0,065 и 0,056). На основу награђених мрежа, конструисани су дијаграми површина одговора чијом ана- лизом су дефинисани услови при којима се постиже оптимална ретенција аналита, односно вредности критеријума сепарације s, а који су подразумевали 54 % метанола на почетку и 79 % на крају програма градијентног елуирања са брзином протока мобилне фазе од 460 mL min -1
PB  - Serbian Chemical Society
T2  - Journal of the Serbian Chemical Society
T1  - Optimization of chromatographic separation of aripiprazole and impurities: Quantitative structure-retention relationship approach
T1  - Оптимизација хроматографског раздвајања арипипразола и нечистоћа: приступ квантификовања односа структуре и ретенционог понашања
VL  - 87
IS  - 5
SP  - 615
EP  - 628
DO  - 10.2298/JSC210709092S
ER  - 

@article{
author = "Svrkota, Bojana and Krmar, Jovana and Protić, Ana and Zečević, Mira and Otašević, Biljana",
year = "2022",
abstract = "A new optimization strategy based on the mixed quantitative struc- ture–retention relationship (QSRR) model is proposed for improving the RP- HPLC separation of aripiprazole and its impurities (IMP A-E). Firstly, experi- mental parameters (EPs), namely mobile phase composition and flow rate, were varied according to Box–Behnken design and thereafter, an artificial neural network (ANN) as a QSRR model was built correlating EPs and sel- ected molecular descriptors (ovality, torsion energy and non-1,4-van der Waals energy) with the log-transformed retention times of the analytes. Values of the root mean square error (RMSE) were used for an estimation of the quality of the ANNs (0.0227, 0.0191 and 0.0230 for the training, verification and test set, respectively). The separations of critical peak pairs on chromatogram (IMP A- B and IMP D-C) were optimized using ANNs for which the EPs served as inputs and the log-transformed separation criteria s as the outputs. They were validated by application of leave-one-out cross-validation (RMSE values 0.065 and 0.056, respectively). The obtained ANNs were used for plotting response surfaces upon which the analyses chromatographic conditions resulting in optimal analytes retention behaviour and the optimal values of the separation criteria s were defined. The optimal conditions were 54 % of methanol at the beginning and 79 % of methanol at the end of gradient elution programme with a mobile phase flow rate of 460 μL min-1, Нова оптимизациона стратегија заснована на грађењу мешовитих модела за кван- тификовање односа структуре и ретенционог понашања (QSRR) предложена је за уна- пређење RP-HPLC раздвајања арипипразола и његових нечистоћа (IMP А-Е). Експери- ментални параметри (EP), састав мобилне фазе и брзина протока, варирани су најпре у складу са Box–Behnken дизајном, а затим је награђена вештачка неуронска мрежа као QSRR модел који повезује ЕP и одабране молекуларне дескрипторе (овалност, торзиона енергија и не-1,4-ван дер Валсова енергија) са логаритамски трансформисаним ретен- ционим временом аналита. Вредности средње квадратне грешке (RMSE) коришћене су за процену квалитета мреже (0,0227, 0,0191 и 0,0230 за тренинг, верификацију и тест сет, редом). Раздвајање критичних парова пикова на хроматограму (IMP А-B и IMP D-C) оптимизовано је коришћењем мрежа за које су ЕP послужили као улази, а логаритамски трансформисани критеријуми сепарације s као излази. Ове мреже су валидиране при- меном унакрсне валидације изостанка (RMSE вредности, редом, 0,065 и 0,056). На основу награђених мрежа, конструисани су дијаграми површина одговора чијом ана- лизом су дефинисани услови при којима се постиже оптимална ретенција аналита, односно вредности критеријума сепарације s, а који су подразумевали 54 % метанола на почетку и 79 % на крају програма градијентног елуирања са брзином протока мобилне фазе од 460 mL min -1",
publisher = "Serbian Chemical Society",
journal = "Journal of the Serbian Chemical Society",
title = "Optimization of chromatographic separation of aripiprazole and impurities: Quantitative structure-retention relationship approach, Оптимизација хроматографског раздвајања арипипразола и нечистоћа: приступ квантификовања односа структуре и ретенционог понашања",
volume = "87",
number = "5",
pages = "615-628",
doi = "10.2298/JSC210709092S"
}

Svrkota, B., Krmar, J., Protić, A., Zečević, M.,& Otašević, B.. (2022). Optimization of chromatographic separation of aripiprazole and impurities: Quantitative structure-retention relationship approach. in Journal of the Serbian Chemical Society
Serbian Chemical Society., 87(5), 615-628.
https://doi.org/10.2298/JSC210709092S

Svrkota B, Krmar J, Protić A, Zečević M, Otašević B. Optimization of chromatographic separation of aripiprazole and impurities: Quantitative structure-retention relationship approach. in Journal of the Serbian Chemical Society. 2022;87(5):615-628.
doi:10.2298/JSC210709092S .

Svrkota, Bojana, Krmar, Jovana, Protić, Ana, Zečević, Mira, Otašević, Biljana, "Optimization of chromatographic separation of aripiprazole and impurities: Quantitative structure-retention relationship approach" in Journal of the Serbian Chemical Society, 87, no. 5 (2022):615-628,
https://doi.org/10.2298/JSC210709092S . .

TY  - CONF
AU  - Đajić, Nevena
AU  - Krmar, Jovana
AU  - Otašević, Biljana
AU  - Malenović, Anđelija
AU  - Protić, Ana
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4694
AB  - Introduction: Cyclodextrin (CD) added to RPHPLC
mobile phase interacts with analytes,
solvent components and stationary phase surface.
Therefore, the retention is influenced by the
analyte’s distribution between CD dissolved in the
mobile phase, free CD and formed inclusion
complex adsorbed onto the stationary phase, and
stationary phase itself (1, 2). The research goal
was to reveal the structural characteristics affecting
the inclusion complexation and retention in these
kinds of chromatographic systems by employing
QSRR-ANN models. Materials and Methods: Mixed QSRR model
included large pool of molecular descriptors,
complex association constants and experimental
parameters towards the retention factor of
risperidone, olanzapine and structurally related
impurities. The experimental space was
adequately covered with central composite design,
while experiments were conducted on Dionex
Ultimate 3000 (U) HPLC. QSRR-ANN modelling
was performed in STATISTICA Neural Networks.
Results: To evaluate the individual influence of
each of the descriptors, the difference in the
highest and lowest retention factor value across
the investigated range of the descriptor’s values
was calculated. The highest ratios were associated
with the following descriptors RDF075m, UE,
Mor04v and CATS2D_08_PL, making them the
most contributing towards the selected output.
RDF075m descriptor shows the three-dimensional
mass distribution calculated at a distance of 7.5 Å
from the geometrical centre of the molecule and it
refers to steric factors at the same distance.
Groups approximately 7.5 Å distant from the
geometrical centre of risperidone, olanzapine and
related compounds in their optimized
conformations were determined. These groups
were the same ones involved in the complexation
process according to previously performed NMR
study. Identified groups and their steric factors are
the most important for the formation of inclusion
complexes, and, in this way, the value of RDF075m
contributes to the retention of the selected
compounds. The importance of Mor04v confirms
the influence of molecular size and shape in
retention in these kinds of chromatographic
systems, while CATS2D_08_PL accounts for
lipophilicity.
Conclusions: The current study resulted in
development of QSRR-ANN with remarkable
performances, which enabled the elucidation of the
molecular features significantly influencing the
retention in β-CD-modified RP-HPLC. The
pronounced effect of molecular structure on
retention was best described through RDF075m,
followed by UE, Mor04v and CATS2D_08_PL.
Retention behaviour is also highly affected by
molecular size and shape, as well as lipophilicity of
the investigated compounds. Moreover, the size
and polarity of the chosen CD should not be
neglected, due to the consequent structural fit.
PB  - Ankara University Faculty of Pharmacy
C3  - The 13th International Symposium on Pharmaceutical Sciences, Ankara, Turkey, 22-25. June 2021, Virtual event
T1  - QSRR-ANN modelling in β-CD-modified RP-HPLC
SP  - 104
EP  - 105
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4694
ER  - 

@conference{
author = "Đajić, Nevena and Krmar, Jovana and Otašević, Biljana and Malenović, Anđelija and Protić, Ana",
year = "2021",
abstract = "Introduction: Cyclodextrin (CD) added to RPHPLC
mobile phase interacts with analytes,
solvent components and stationary phase surface.
Therefore, the retention is influenced by the
analyte’s distribution between CD dissolved in the
mobile phase, free CD and formed inclusion
complex adsorbed onto the stationary phase, and
stationary phase itself (1, 2). The research goal
was to reveal the structural characteristics affecting
the inclusion complexation and retention in these
kinds of chromatographic systems by employing
QSRR-ANN models. Materials and Methods: Mixed QSRR model
included large pool of molecular descriptors,
complex association constants and experimental
parameters towards the retention factor of
risperidone, olanzapine and structurally related
impurities. The experimental space was
adequately covered with central composite design,
while experiments were conducted on Dionex
Ultimate 3000 (U) HPLC. QSRR-ANN modelling
was performed in STATISTICA Neural Networks.
Results: To evaluate the individual influence of
each of the descriptors, the difference in the
highest and lowest retention factor value across
the investigated range of the descriptor’s values
was calculated. The highest ratios were associated
with the following descriptors RDF075m, UE,
Mor04v and CATS2D_08_PL, making them the
most contributing towards the selected output.
RDF075m descriptor shows the three-dimensional
mass distribution calculated at a distance of 7.5 Å
from the geometrical centre of the molecule and it
refers to steric factors at the same distance.
Groups approximately 7.5 Å distant from the
geometrical centre of risperidone, olanzapine and
related compounds in their optimized
conformations were determined. These groups
were the same ones involved in the complexation
process according to previously performed NMR
study. Identified groups and their steric factors are
the most important for the formation of inclusion
complexes, and, in this way, the value of RDF075m
contributes to the retention of the selected
compounds. The importance of Mor04v confirms
the influence of molecular size and shape in
retention in these kinds of chromatographic
systems, while CATS2D_08_PL accounts for
lipophilicity.
Conclusions: The current study resulted in
development of QSRR-ANN with remarkable
performances, which enabled the elucidation of the
molecular features significantly influencing the
retention in β-CD-modified RP-HPLC. The
pronounced effect of molecular structure on
retention was best described through RDF075m,
followed by UE, Mor04v and CATS2D_08_PL.
Retention behaviour is also highly affected by
molecular size and shape, as well as lipophilicity of
the investigated compounds. Moreover, the size
and polarity of the chosen CD should not be
neglected, due to the consequent structural fit.",
publisher = "Ankara University Faculty of Pharmacy",
journal = "The 13th International Symposium on Pharmaceutical Sciences, Ankara, Turkey, 22-25. June 2021, Virtual event",
title = "QSRR-ANN modelling in β-CD-modified RP-HPLC",
pages = "104-105",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4694"
}

Đajić, N., Krmar, J., Otašević, B., Malenović, A.,& Protić, A.. (2021). QSRR-ANN modelling in β-CD-modified RP-HPLC. in The 13th International Symposium on Pharmaceutical Sciences, Ankara, Turkey, 22-25. June 2021, Virtual event
Ankara University Faculty of Pharmacy., 104-105.
https://hdl.handle.net/21.15107/rcub_farfar_4694

Đajić N, Krmar J, Otašević B, Malenović A, Protić A. QSRR-ANN modelling in β-CD-modified RP-HPLC. in The 13th International Symposium on Pharmaceutical Sciences, Ankara, Turkey, 22-25. June 2021, Virtual event. 2021;:104-105.
https://hdl.handle.net/21.15107/rcub_farfar_4694 .

Đajić, Nevena, Krmar, Jovana, Otašević, Biljana, Malenović, Anđelija, Protić, Ana, "QSRR-ANN modelling in β-CD-modified RP-HPLC" in The 13th International Symposium on Pharmaceutical Sciences, Ankara, Turkey, 22-25. June 2021, Virtual event (2021):104-105,
https://hdl.handle.net/21.15107/rcub_farfar_4694 .

TY  - CONF
AU  - Svrkota, Bojana
AU  - Krmar, Jovana
AU  - Protić, Ana
AU  - Zečević, Mira
AU  - Otašević, Biljana
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4697
AB  - One of widely used drug group refers to drugs that act through adrenergic system. In following
research, the intent was to develop High Performance Liquid Chromatography (HPLC) method for
separation of adrenergic drugs. Therefore, selected mixture of analytes contained bisoprolol (BP),
fenoterole (FT), doxazosin (DOX), tetrahydrazoline (TH) and lofexidine (LOF). One of the
advantages of this method reflects in expanding knowledge about the analytical behaviour of
lofexidine, which is limited. Since all of selected analytes are basic in nature, mixed-mode column,
which includes reverse phase (RP) and weak cation exchange (WCX) interactions, was considered as
adequate for this HPLC analysis. The pronunciation one of two separation mechanisms depends on
mobile phase content and pH, and as a consequence has the potential of selectivity modulation [1].
Analyses were performed on HPLC Thermo Acclaim Mixed Mode WCX-1 (3 μm, 2.1 x 150 mm)
column. During screening phase, factors of significant influence on cationic analytes behaviour were
determinated. For that reason, column temperature (30-38°C) and mobile phase composition
parameters (acetonitrile content (30-50% (v/v)), pH (3.8-5.6) and ionic strength (20-40 mM) of
aqueous part of mobile phase) were selected for optimization. Design of Experiments (DoE) was used
for simultaneous optimization of selected factors. Experimental plan was in line with face-centered
Central Composite Design. Optimization goals were set in order to adequately separate all critical
peak pairs, and execute the analysis in reasonable time. Since selectivity in mixed-mode HPLC can
be governed through mobile phase content, selectivity factor (α) values of critical peak pairs were set
as optimization goals (αBP/FT, αTH/BP, αLOF/DOX > 1.2). The retention factor of last eluting analyte (kDOX)
was desired not to be greater than 10, in order to assure the rational analysis time. Experimental plan
and mathematical models were obtained with Design-Expert 7.0.0 software. Obtained models were
statistically evaluated (R2, pred. R2 and adj. R2 > 0.99). The most pronounced effect on followed
responses had the organic solvent content, whose increase lead to αTH/BP
enhancing, and had the
opposite effect on αBP/FT, αLOF/DOX and kDOX. Higher ionic strength corresponded to better separation
of BP from both FT and TH. This can be assigned to competitive behaviour between analytes and
ions present in mobile phase [2]. Time analysis shortening resulted as a consequence of higher values
of organic solvent, ionic strength and temperature. However, mobile phase pH had the opposite effect,
which can be related to more expressed cationic interactions and greater retention of basic analytes
[2].
Taking into account effects of all factors, and according to generated Derringer’s desirability function
for multiobjective decision making, the values of the factors that give the optimal responses are
selected to be 44% of acetonitrile, ionic strength 36 mM, temperature of 38°C and mobile phase pH
of 5.1.
PB  - Aristotle University of Thessaloniki
PB  - National Technical University of Athens
C3  - IMA-2021, 12 International Conference on Instrumental Methods of Analysis, Modern Trends and Applications, 20-23 September 2021, Virtual event
T1  - Optimization of mixed-mode HPLC method intended for analysis of adrenergic drugs
SP  - 119
EP  - 119
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4697
ER  - 

@conference{
author = "Svrkota, Bojana and Krmar, Jovana and Protić, Ana and Zečević, Mira and Otašević, Biljana",
year = "2021",
abstract = "One of widely used drug group refers to drugs that act through adrenergic system. In following
research, the intent was to develop High Performance Liquid Chromatography (HPLC) method for
separation of adrenergic drugs. Therefore, selected mixture of analytes contained bisoprolol (BP),
fenoterole (FT), doxazosin (DOX), tetrahydrazoline (TH) and lofexidine (LOF). One of the
advantages of this method reflects in expanding knowledge about the analytical behaviour of
lofexidine, which is limited. Since all of selected analytes are basic in nature, mixed-mode column,
which includes reverse phase (RP) and weak cation exchange (WCX) interactions, was considered as
adequate for this HPLC analysis. The pronunciation one of two separation mechanisms depends on
mobile phase content and pH, and as a consequence has the potential of selectivity modulation [1].
Analyses were performed on HPLC Thermo Acclaim Mixed Mode WCX-1 (3 μm, 2.1 x 150 mm)
column. During screening phase, factors of significant influence on cationic analytes behaviour were
determinated. For that reason, column temperature (30-38°C) and mobile phase composition
parameters (acetonitrile content (30-50% (v/v)), pH (3.8-5.6) and ionic strength (20-40 mM) of
aqueous part of mobile phase) were selected for optimization. Design of Experiments (DoE) was used
for simultaneous optimization of selected factors. Experimental plan was in line with face-centered
Central Composite Design. Optimization goals were set in order to adequately separate all critical
peak pairs, and execute the analysis in reasonable time. Since selectivity in mixed-mode HPLC can
be governed through mobile phase content, selectivity factor (α) values of critical peak pairs were set
as optimization goals (αBP/FT, αTH/BP, αLOF/DOX > 1.2). The retention factor of last eluting analyte (kDOX)
was desired not to be greater than 10, in order to assure the rational analysis time. Experimental plan
and mathematical models were obtained with Design-Expert 7.0.0 software. Obtained models were
statistically evaluated (R2, pred. R2 and adj. R2 > 0.99). The most pronounced effect on followed
responses had the organic solvent content, whose increase lead to αTH/BP
enhancing, and had the
opposite effect on αBP/FT, αLOF/DOX and kDOX. Higher ionic strength corresponded to better separation
of BP from both FT and TH. This can be assigned to competitive behaviour between analytes and
ions present in mobile phase [2]. Time analysis shortening resulted as a consequence of higher values
of organic solvent, ionic strength and temperature. However, mobile phase pH had the opposite effect,
which can be related to more expressed cationic interactions and greater retention of basic analytes
[2].
Taking into account effects of all factors, and according to generated Derringer’s desirability function
for multiobjective decision making, the values of the factors that give the optimal responses are
selected to be 44% of acetonitrile, ionic strength 36 mM, temperature of 38°C and mobile phase pH
of 5.1.",
publisher = "Aristotle University of Thessaloniki, National Technical University of Athens",
journal = "IMA-2021, 12 International Conference on Instrumental Methods of Analysis, Modern Trends and Applications, 20-23 September 2021, Virtual event",
title = "Optimization of mixed-mode HPLC method intended for analysis of adrenergic drugs",
pages = "119-119",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4697"
}

Svrkota, B., Krmar, J., Protić, A., Zečević, M.,& Otašević, B.. (2021). Optimization of mixed-mode HPLC method intended for analysis of adrenergic drugs. in IMA-2021, 12 International Conference on Instrumental Methods of Analysis, Modern Trends and Applications, 20-23 September 2021, Virtual event
Aristotle University of Thessaloniki., 119-119.
https://hdl.handle.net/21.15107/rcub_farfar_4697

Svrkota B, Krmar J, Protić A, Zečević M, Otašević B. Optimization of mixed-mode HPLC method intended for analysis of adrenergic drugs. in IMA-2021, 12 International Conference on Instrumental Methods of Analysis, Modern Trends and Applications, 20-23 September 2021, Virtual event. 2021;:119-119.
https://hdl.handle.net/21.15107/rcub_farfar_4697 .

Svrkota, Bojana, Krmar, Jovana, Protić, Ana, Zečević, Mira, Otašević, Biljana, "Optimization of mixed-mode HPLC method intended for analysis of adrenergic drugs" in IMA-2021, 12 International Conference on Instrumental Methods of Analysis, Modern Trends and Applications, 20-23 September 2021, Virtual event (2021):119-119,
https://hdl.handle.net/21.15107/rcub_farfar_4697 .

TY  - JOUR
AU  - Stojanović, Jevrem
AU  - Krmar, Jovana
AU  - Protić, Ana
AU  - Svrkota, Bojana
AU  - Đajić, Nevena
AU  - Otašević, Biljana
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3951
AB  - Design of Experiments (DoE) is an indispensable tool in contemporary drug analysis as it
simultaneously balances a number of chromatographic parameters to ensure optimal separation
in High Pressure Liquid Chromatography (HPLC). This manuscript briefly outlines the theoretical
background of the DoE and provides step-by-step instruction for its implementation in HPLC
pharmaceutical practice. It particularly discusses the classification of various design types and
their possibilities to rationalize the different stages of HPLC method development workflow, such
as the selection of the most influential factors, factors optimization and assessment of the method
robustness. Additionally, the application of the DoE-based Analytical Quality by Design (AQbD)
concept in the LC method development has been summarized. Recent achievements in the use of
DoE in the development of stability-indicating LC and hyphenated LC-MS methods have also
been briefly reported. Performing of Quantitative structure retention relationship (QSRR) study
enhanced with DoE-based data collection was recomended as a future perspective in description
of retention in HPLC system.
AB  - Dizajn eksperimenata (DoE) je nezaobilazan alat u savremenoj analizi lekova budući da istovremeno balansira niz hromatografskih parametara kako bi se osiguralo optimalno razdvajanje u tečnoj hromatografiji pod visokim pritiskom (HPLC). Prikazana je teorijska osnova DOE i data su detaljna uputstva za njegovu primenu u HPLC ispitivanjima u farmaciji. Naročito se govori o klasifikaciji brojnih tipova dizajna i njihovim mogućnostima za racionalizaciju različitih faza tokom procesa razvoja HPLC metode, kao što su izbor najuticajnijih faktora, optimizacija faktora i procena robusnosti metode. Dodatno, sumirana je primena DOE kao sastavnog dela koncepta ugradnje kvaliteta u proizvod u domenu razvoja analitičkih metoda (AQbD) zasnovanih na HPLC tehnici. Takođe su prikazana i nedavna dostignuća u primeni DOE u razvoju LC metoda koje su pogodne za ispitivanje stabilnosti lekova, kao i LC-MS metoda. U budućoj perspektivi, preporučeno je izvođenje ispitivanja kvantitativnog odnosa između strukture i retencionog ponašanja (QSRR) analita u HPLC sistemu na osnovu podataka dobijenih primenom DOE.
PB  - Beograd : Savez farmaceutskih udruženja Srbije
T2  - Arhiv za farmaciju
T1  - Experimental design in HPLC separation of pharmaceuticals
T1  - Primena eksperimentalnog dizajna za razdvajanje lekova HPLC metodom
VL  - 71
IS  - 4
SP  - 279
EP  - 301
DO  - 10.5937/arhfarm71-32480
ER  - 

@article{
author = "Stojanović, Jevrem and Krmar, Jovana and Protić, Ana and Svrkota, Bojana and Đajić, Nevena and Otašević, Biljana",
year = "2021",
abstract = "Design of Experiments (DoE) is an indispensable tool in contemporary drug analysis as it
simultaneously balances a number of chromatographic parameters to ensure optimal separation
in High Pressure Liquid Chromatography (HPLC). This manuscript briefly outlines the theoretical
background of the DoE and provides step-by-step instruction for its implementation in HPLC
pharmaceutical practice. It particularly discusses the classification of various design types and
their possibilities to rationalize the different stages of HPLC method development workflow, such
as the selection of the most influential factors, factors optimization and assessment of the method
robustness. Additionally, the application of the DoE-based Analytical Quality by Design (AQbD)
concept in the LC method development has been summarized. Recent achievements in the use of
DoE in the development of stability-indicating LC and hyphenated LC-MS methods have also
been briefly reported. Performing of Quantitative structure retention relationship (QSRR) study
enhanced with DoE-based data collection was recomended as a future perspective in description
of retention in HPLC system., Dizajn eksperimenata (DoE) je nezaobilazan alat u savremenoj analizi lekova budući da istovremeno balansira niz hromatografskih parametara kako bi se osiguralo optimalno razdvajanje u tečnoj hromatografiji pod visokim pritiskom (HPLC). Prikazana je teorijska osnova DOE i data su detaljna uputstva za njegovu primenu u HPLC ispitivanjima u farmaciji. Naročito se govori o klasifikaciji brojnih tipova dizajna i njihovim mogućnostima za racionalizaciju različitih faza tokom procesa razvoja HPLC metode, kao što su izbor najuticajnijih faktora, optimizacija faktora i procena robusnosti metode. Dodatno, sumirana je primena DOE kao sastavnog dela koncepta ugradnje kvaliteta u proizvod u domenu razvoja analitičkih metoda (AQbD) zasnovanih na HPLC tehnici. Takođe su prikazana i nedavna dostignuća u primeni DOE u razvoju LC metoda koje su pogodne za ispitivanje stabilnosti lekova, kao i LC-MS metoda. U budućoj perspektivi, preporučeno je izvođenje ispitivanja kvantitativnog odnosa između strukture i retencionog ponašanja (QSRR) analita u HPLC sistemu na osnovu podataka dobijenih primenom DOE.",
publisher = "Beograd : Savez farmaceutskih udruženja Srbije",
journal = "Arhiv za farmaciju",
title = "Experimental design in HPLC separation of pharmaceuticals, Primena eksperimentalnog dizajna za razdvajanje lekova HPLC metodom",
volume = "71",
number = "4",
pages = "279-301",
doi = "10.5937/arhfarm71-32480"
}

Stojanović, J., Krmar, J., Protić, A., Svrkota, B., Đajić, N.,& Otašević, B.. (2021). Experimental design in HPLC separation of pharmaceuticals. in Arhiv za farmaciju
Beograd : Savez farmaceutskih udruženja Srbije., 71(4), 279-301.
https://doi.org/10.5937/arhfarm71-32480

Stojanović J, Krmar J, Protić A, Svrkota B, Đajić N, Otašević B. Experimental design in HPLC separation of pharmaceuticals. in Arhiv za farmaciju. 2021;71(4):279-301.
doi:10.5937/arhfarm71-32480 .

Stojanović, Jevrem, Krmar, Jovana, Protić, Ana, Svrkota, Bojana, Đajić, Nevena, Otašević, Biljana, "Experimental design in HPLC separation of pharmaceuticals" in Arhiv za farmaciju, 71, no. 4 (2021):279-301,
https://doi.org/10.5937/arhfarm71-32480 . .

TY  - CONF
AU  - Milenković, Milan
AU  - Đajić, Nevena
AU  - Krmar, Jovana
AU  - Rašević, Marija
AU  - Malenović, Anđelija
AU  - Otašević, Biljana
AU  - Protić, Ana
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4696
AB  - Introduction: Gradient elution HPLC finds its
purpose in simultaneous analyses of solutes
covering wide range of polarities. However, the
instrument related factors, especially dwell volume, are frequently responsible for fizzy transfer and
short life cycle of the gradient elution method.
Therefore, it is advisable to incorporate dwell
volume into the optimization stage and avoid
transfer related failures. The chemometric
approach would enable selection of optimal
chromatographic conditions for different HPLC
instruments. The aim of this study was to propose
and test this approach in gradient elution method’s
development.
Materials and Methods: The experiments were
carried out on three chromatographic systems
(UPLC, UHPLC and HPLC), while the separation
was achieved on Kinetex C18 Core-shell column
(100 mm × 2.1 mm, 2.6 μm particle size). Design
of experiments was constructed in Design-Expert
11.0. Indirect modeling, grid point search and
graphical presentations were done in Matlab
7.10.0.
Results: Dabigatrane etexilate mesylate and nine
structurally related compounds were selected as
suitable model mixture due to its complexity and
polarity. Method development was supported with
experimental design methodology, Placket –
Burman for screening and D-optimal design for
optimization purposes. Dwell volumes were
included in the optimization phase and in this way
the same optimal chromatographic conditions for
all three instruments were selected. They included 10 mM ammonium acetate buffer
with pH set to 4.9 using acetic acid, and
acetonitrile. The components of the mobile phase
were pumped into chromatographic system with
flow rate of 400 μL min-1 in a linear gradient mode:
at 0 minutes 24% (v/v) acetonitrile and 76% (v/v) of
buffer solution, at 15 minutes 54% (v/v) acetonitrile
and 46% (v/v) buffer solution. At 16 minutes the
acetonitrile content was back to 24% (v/v) and 76%
(v/v) of buffer solution. The re-equilibration time
was set to 5 minutes. The examined
chromatographic region is graphically presented
and optimal conditions are noticed as the cross
sections (yellow dots). The method was validated
and confirmed its utility on all instruments.
Conclusions: The proposed methodology
demonstrated its ability to predict joint optimal
chromatographic conditions for instruments with different values of dwell volume. The potential was
confirmed on complex model mixture and
instruments significantly differing in dwell volume
values. In this way the gap between developing
and routine needs could be overwhelmed, followed
by facilitated transfer of methods.
PB  - Ankara University Faculty of Pharmacy
C3  - 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey
T1  - The novel approach towards gradient elution HPLC method development
SP  - 227
EP  - 228
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4696
ER  - 

@conference{
author = "Milenković, Milan and Đajić, Nevena and Krmar, Jovana and Rašević, Marija and Malenović, Anđelija and Otašević, Biljana and Protić, Ana",
year = "2021",
abstract = "Introduction: Gradient elution HPLC finds its
purpose in simultaneous analyses of solutes
covering wide range of polarities. However, the
instrument related factors, especially dwell volume, are frequently responsible for fizzy transfer and
short life cycle of the gradient elution method.
Therefore, it is advisable to incorporate dwell
volume into the optimization stage and avoid
transfer related failures. The chemometric
approach would enable selection of optimal
chromatographic conditions for different HPLC
instruments. The aim of this study was to propose
and test this approach in gradient elution method’s
development.
Materials and Methods: The experiments were
carried out on three chromatographic systems
(UPLC, UHPLC and HPLC), while the separation
was achieved on Kinetex C18 Core-shell column
(100 mm × 2.1 mm, 2.6 μm particle size). Design
of experiments was constructed in Design-Expert
11.0. Indirect modeling, grid point search and
graphical presentations were done in Matlab
7.10.0.
Results: Dabigatrane etexilate mesylate and nine
structurally related compounds were selected as
suitable model mixture due to its complexity and
polarity. Method development was supported with
experimental design methodology, Placket –
Burman for screening and D-optimal design for
optimization purposes. Dwell volumes were
included in the optimization phase and in this way
the same optimal chromatographic conditions for
all three instruments were selected. They included 10 mM ammonium acetate buffer
with pH set to 4.9 using acetic acid, and
acetonitrile. The components of the mobile phase
were pumped into chromatographic system with
flow rate of 400 μL min-1 in a linear gradient mode:
at 0 minutes 24% (v/v) acetonitrile and 76% (v/v) of
buffer solution, at 15 minutes 54% (v/v) acetonitrile
and 46% (v/v) buffer solution. At 16 minutes the
acetonitrile content was back to 24% (v/v) and 76%
(v/v) of buffer solution. The re-equilibration time
was set to 5 minutes. The examined
chromatographic region is graphically presented
and optimal conditions are noticed as the cross
sections (yellow dots). The method was validated
and confirmed its utility on all instruments.
Conclusions: The proposed methodology
demonstrated its ability to predict joint optimal
chromatographic conditions for instruments with different values of dwell volume. The potential was
confirmed on complex model mixture and
instruments significantly differing in dwell volume
values. In this way the gap between developing
and routine needs could be overwhelmed, followed
by facilitated transfer of methods.",
publisher = "Ankara University Faculty of Pharmacy",
journal = "13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey",
title = "The novel approach towards gradient elution HPLC method development",
pages = "227-228",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4696"
}

Milenković, M., Đajić, N., Krmar, J., Rašević, M., Malenović, A., Otašević, B.,& Protić, A.. (2021). The novel approach towards gradient elution HPLC method development. in 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey
Ankara University Faculty of Pharmacy., 227-228.
https://hdl.handle.net/21.15107/rcub_farfar_4696

Milenković M, Đajić N, Krmar J, Rašević M, Malenović A, Otašević B, Protić A. The novel approach towards gradient elution HPLC method development. in 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey. 2021;:227-228.
https://hdl.handle.net/21.15107/rcub_farfar_4696 .

Milenković, Milan, Đajić, Nevena, Krmar, Jovana, Rašević, Marija, Malenović, Anđelija, Otašević, Biljana, Protić, Ana, "The novel approach towards gradient elution HPLC method development" in 13th International Symposium on Pharmaceutical Sciences (ISOPS), June 22-25, 2021, Ankara, Turkey (2021):227-228,
https://hdl.handle.net/21.15107/rcub_farfar_4696 .

TY  - CONF
AU  - Đajić, Nevena
AU  - Krmar, Jovana
AU  - Otašević, Biljana
AU  - Protić, Ana
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4680
AB  - Burden of potentially harmful effects of analytical techniques used in pharmaceutical analysis
on human health and environment has recently shown a dramatic increase (1). Therefore, analytical
methods able to minimize the production of hazardous waste and use less energy are developing.
Reversed-phase high performance liquid chromatography (RP-HPLC) is the most frequently used
technique in determination of various compounds, due to its representative analytical features (2).
However, RP-HPLC is associated with a substantial amount of waste. Simultaneously, pharmaceutical
industry seeks for technologies that produce high resolution within a reduced analysis time without
loss of separation efficiency (3). Using fully porous sub-2-μm stationary phase particles provides better
resolution in comparison to traditional HPLC stationary phases. However, it causes high column
backpressure and thus initiated development of ultra high performance liquid chromatography
(UHPLC) instruments. Along with reduced particle size, UHPLC uses shorter columns, which leads to
diminished analysis time and minimized production of waste comparing to HPLC. In that respect,
UHPLC method for separation of dronedarone hydrochloride and its degradation products was
developed utilizing experimental design methodology. Model mixture was selected to cover diversity in
physicochemical characteristics. Compounds’ varying polarity represents a challenge from the
analytical point of view. Dronedarone hydrochloride is lipophilic, thus requires substantial amounts of
organic solvent for its elution. In that respect, there is a recognized need for developing a
chromatographic method able to separate the aforementioned compounds with reduced organic
solvent consumption and/or analysis time. Preliminary experiments determined factors with
significant influence on retention. These factors, namely the initial and final content of acetonitrile and
time of gradient were varied according to central composite design. The goal was to achieve satisfying
separation between critical peak pairs. Firstly, mathematical models for the time of start and end of
peak of each critical pair were obtained. Afterwards, the separation factor (S) standing for the distance
between peaks in one critical pair was indirectly modelled. An appropriate separation is achieved if S is
higher than zero, which was accomplished with the initial content of acetonitrile of 6% (v/v), the final
content of acetonitrile of 50% (v/v), and the gradient duration of 5 min. Ecological acceptability of
UHPLC method was evaluated with green analytical procedure index (GAPI), which confirmed eco-
friendliness. GAPI showed that the most critical segment is the sample collection and that the
advantage should be given to UHPLC over HPLC in terms of energy saving.
AB  - Opterećenje štetnim uticajem analitičkih tehnika koje se koriste u farmaceutskoj
analizi na zdravlje ljudi i životnu sredinu je doživelo dramatičan porast (1). Iz tog razloga,
razvijaju se metode koje generišu manje štetnog otpada i koriste manje energije. Reverzno-
fazna tečna hromatografija pod visokim pritiskom (RP-HPLC) je najčešće korišćena tehnika u
određivanju različitih jedinjenja, zahvaljujući svojim reprezentativnim analitičkim
osobinama (2). Sa druge strane, primenom RP-HPLC proizvode se značajne količine otpada.
U isto vreme, farmaceutska industrija je u potrazi za tehnikama, koje će obezbediti visoku
rezoluciju u redukovanom vremenu trajanja analize, bez gubitka efikasnosti razdvajanja (3).
Korišćenjem stacionarnih faze sa potpuno poroznim česticama veličine ispod 2 μm
obezbeđuje bolju rezoluciju u poređenju sa tradicionalnim HPLC stacionarnim fazama.
Međutim, one dovode do visokih pritisaka, koji su kompatibilni sa instrumentima za
izvođenje hromatografije pod veoma visokim pritiskom (UHPLC). UHPLC instrumenti koriste
više pritiske u kraćim kolona sa smanjenom veličinom čestica, što dovodi do kraćeg trajanja
analize i manje produkcije otpada nego kod HPLC. UHPLC metoda za razdvajanje dronedaron
hidrohlorida i degradacionih proizvoda razvijena je korišćenjem metodologije
eksperimentalnog dizajna. Model smeša je odbrana kako bi se pokrile raznovrsne fizičko-
hemijske osobine. Različita polarnost ispitivanih jedinjenja predstavljala izazov sa aspekta
analitike. Dronedaron hidrohlorid je lipofilan, pa je za njegovo eluiranje potrebna značajna
količina organskog rastvarača. Prema tome, postoji potreba za razvojem hromatografske
metode za razdvajanje ovih jedinjenja sa redukovanom upotrebom organskog rastvarača i/ili
smanjenim trajanjem analize. Preliminarni eksperimenti su odredili faktore sa značajnim
uticajem na retenciju. Ovi faktori, početni i krajnji udeo acetonitrila i vreme trajanja
gradijenta su varirani prema centralnom kompozicionom dizajnu. Cilj je bio da se postigne
zadovoljavajuće razdvajanje između kritičnih parova. Prvo su dobijeni matematički modeli
za vreme početka i kraja pika svakog kritičnog para. Nakon toga, indirektno je modelovan
separacioni faktor (S), koji predstavlja razdaljinu između dva pika jednog kritičnog para. Do
odgovarajućeg razdvajanja dolazi ukoliko je S veći od 0, što se postiže sa početnim udelom
acetonitrila od 6% (v/v), krajnjim udelom acetonitrila od 50% (v/v) i trajanjem gradijenta
od 5 minuta. Ekološka prihvatljivost UHPLC metode je potvrđena određivanjem indeksa
ekološke prihvatljivosti analitičke procedure (GAPI). GAPI je pokazao da je najkritičniji
segment prikupljanje uzorka, kao i da u pogledu energetske uštede prednost nad HPLC treba
dati UHPLC metodi.
PB  - Savez farmaceutskih udruženja Srbije (SFUS)
C3  - Arhiv za farmaciju
T1  - Chemometrically supported UHPLC method development: a strategy for achieving eco‐friendliness
T1  - Hemometrijski podržan razvoj UHPLC metode: strategija za postizanje ekološke prihvatljivosti
VL  - 71
IS  - 5 suplement
SP  - S124
EP  - S125
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4680
ER  - 

@conference{
author = "Đajić, Nevena and Krmar, Jovana and Otašević, Biljana and Protić, Ana",
year = "2021",
abstract = "Burden of potentially harmful effects of analytical techniques used in pharmaceutical analysis
on human health and environment has recently shown a dramatic increase (1). Therefore, analytical
methods able to minimize the production of hazardous waste and use less energy are developing.
Reversed-phase high performance liquid chromatography (RP-HPLC) is the most frequently used
technique in determination of various compounds, due to its representative analytical features (2).
However, RP-HPLC is associated with a substantial amount of waste. Simultaneously, pharmaceutical
industry seeks for technologies that produce high resolution within a reduced analysis time without
loss of separation efficiency (3). Using fully porous sub-2-μm stationary phase particles provides better
resolution in comparison to traditional HPLC stationary phases. However, it causes high column
backpressure and thus initiated development of ultra high performance liquid chromatography
(UHPLC) instruments. Along with reduced particle size, UHPLC uses shorter columns, which leads to
diminished analysis time and minimized production of waste comparing to HPLC. In that respect,
UHPLC method for separation of dronedarone hydrochloride and its degradation products was
developed utilizing experimental design methodology. Model mixture was selected to cover diversity in
physicochemical characteristics. Compounds’ varying polarity represents a challenge from the
analytical point of view. Dronedarone hydrochloride is lipophilic, thus requires substantial amounts of
organic solvent for its elution. In that respect, there is a recognized need for developing a
chromatographic method able to separate the aforementioned compounds with reduced organic
solvent consumption and/or analysis time. Preliminary experiments determined factors with
significant influence on retention. These factors, namely the initial and final content of acetonitrile and
time of gradient were varied according to central composite design. The goal was to achieve satisfying
separation between critical peak pairs. Firstly, mathematical models for the time of start and end of
peak of each critical pair were obtained. Afterwards, the separation factor (S) standing for the distance
between peaks in one critical pair was indirectly modelled. An appropriate separation is achieved if S is
higher than zero, which was accomplished with the initial content of acetonitrile of 6% (v/v), the final
content of acetonitrile of 50% (v/v), and the gradient duration of 5 min. Ecological acceptability of
UHPLC method was evaluated with green analytical procedure index (GAPI), which confirmed eco-
friendliness. GAPI showed that the most critical segment is the sample collection and that the
advantage should be given to UHPLC over HPLC in terms of energy saving., Opterećenje štetnim uticajem analitičkih tehnika koje se koriste u farmaceutskoj
analizi na zdravlje ljudi i životnu sredinu je doživelo dramatičan porast (1). Iz tog razloga,
razvijaju se metode koje generišu manje štetnog otpada i koriste manje energije. Reverzno-
fazna tečna hromatografija pod visokim pritiskom (RP-HPLC) je najčešće korišćena tehnika u
određivanju različitih jedinjenja, zahvaljujući svojim reprezentativnim analitičkim
osobinama (2). Sa druge strane, primenom RP-HPLC proizvode se značajne količine otpada.
U isto vreme, farmaceutska industrija je u potrazi za tehnikama, koje će obezbediti visoku
rezoluciju u redukovanom vremenu trajanja analize, bez gubitka efikasnosti razdvajanja (3).
Korišćenjem stacionarnih faze sa potpuno poroznim česticama veličine ispod 2 μm
obezbeđuje bolju rezoluciju u poređenju sa tradicionalnim HPLC stacionarnim fazama.
Međutim, one dovode do visokih pritisaka, koji su kompatibilni sa instrumentima za
izvođenje hromatografije pod veoma visokim pritiskom (UHPLC). UHPLC instrumenti koriste
više pritiske u kraćim kolona sa smanjenom veličinom čestica, što dovodi do kraćeg trajanja
analize i manje produkcije otpada nego kod HPLC. UHPLC metoda za razdvajanje dronedaron
hidrohlorida i degradacionih proizvoda razvijena je korišćenjem metodologije
eksperimentalnog dizajna. Model smeša je odbrana kako bi se pokrile raznovrsne fizičko-
hemijske osobine. Različita polarnost ispitivanih jedinjenja predstavljala izazov sa aspekta
analitike. Dronedaron hidrohlorid je lipofilan, pa je za njegovo eluiranje potrebna značajna
količina organskog rastvarača. Prema tome, postoji potreba za razvojem hromatografske
metode za razdvajanje ovih jedinjenja sa redukovanom upotrebom organskog rastvarača i/ili
smanjenim trajanjem analize. Preliminarni eksperimenti su odredili faktore sa značajnim
uticajem na retenciju. Ovi faktori, početni i krajnji udeo acetonitrila i vreme trajanja
gradijenta su varirani prema centralnom kompozicionom dizajnu. Cilj je bio da se postigne
zadovoljavajuće razdvajanje između kritičnih parova. Prvo su dobijeni matematički modeli
za vreme početka i kraja pika svakog kritičnog para. Nakon toga, indirektno je modelovan
separacioni faktor (S), koji predstavlja razdaljinu između dva pika jednog kritičnog para. Do
odgovarajućeg razdvajanja dolazi ukoliko je S veći od 0, što se postiže sa početnim udelom
acetonitrila od 6% (v/v), krajnjim udelom acetonitrila od 50% (v/v) i trajanjem gradijenta
od 5 minuta. Ekološka prihvatljivost UHPLC metode je potvrđena određivanjem indeksa
ekološke prihvatljivosti analitičke procedure (GAPI). GAPI je pokazao da je najkritičniji
segment prikupljanje uzorka, kao i da u pogledu energetske uštede prednost nad HPLC treba
dati UHPLC metodi.",
publisher = "Savez farmaceutskih udruženja Srbije (SFUS)",
journal = "Arhiv za farmaciju",
title = "Chemometrically supported UHPLC method development: a strategy for achieving eco‐friendliness, Hemometrijski podržan razvoj UHPLC metode: strategija za postizanje ekološke prihvatljivosti",
volume = "71",
number = "5 suplement",
pages = "S124-S125",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4680"
}

Đajić, N., Krmar, J., Otašević, B.,& Protić, A.. (2021). Chemometrically supported UHPLC method development: a strategy for achieving eco‐friendliness. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije (SFUS)., 71(5 suplement), S124-S125.
https://hdl.handle.net/21.15107/rcub_farfar_4680

Đajić N, Krmar J, Otašević B, Protić A. Chemometrically supported UHPLC method development: a strategy for achieving eco‐friendliness. in Arhiv za farmaciju. 2021;71(5 suplement):S124-S125.
https://hdl.handle.net/21.15107/rcub_farfar_4680 .

Đajić, Nevena, Krmar, Jovana, Otašević, Biljana, Protić, Ana, "Chemometrically supported UHPLC method development: a strategy for achieving eco‐friendliness" in Arhiv za farmaciju, 71, no. 5 suplement (2021):S124-S125,
https://hdl.handle.net/21.15107/rcub_farfar_4680 .

TY  - CONF
AU  - Krmar, Jovana
AU  - Svrkota, Bojana
AU  - Đajić, Nevena
AU  - Protić, Ana
AU  - Otašević, Biljana
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4679
AB  - With respect to significant market presence (50%), the analysis of pharmaceuticals containing
counterions is a crucial component of the drug development life cycle, quality control and lot release
processes (1). Mixed-Mode Chromatography (MMC) offers the ability to simultaneously separate
cationic and anionic species within a single run, streamlining the laboratory processes (2). However,
the detection of typical counterions leaves analysts little room for maneuver. In recent years, the
counterions are efficiently detected with the help of Charged Aerosol Detector (CAD) that generates a
signal independent of the chemical structure (3). In this regard, the use of MMC-CAD hyphenated
technique rationalizes the number of individual analytical activities required for analyte and
counterion testing, causes no resource depletion and ultimately supports the concept of sustainability
in contemporary drug analysis. In this paper, the influence of the CAD parameters on the response of
diclofenac potassium and tramadol hydrochloride was studied performing systematic variations. The
analyses were carried out on Acclaim™ Mixed-mode WCX-1 (2.1 x 150 nm, 3 μm) column that provides
both hydrophobic reversed-phase and weak cation-exchange properties. Satisfactory separation of the
active pharmaceutical ingredients and their counterions was achieved using a mixture of 90 mM
acetate buffer at pH 5 (A) and acetonitrile (B). The isocratic elution (40% B) was performed at a flow
rate of 0.4 mL/min. Based on preliminary experiments, the following variables were identified as
significant and, thus, tested at the listed values: evaporation temperature (35ºC and 50ºC), filter
constant (1 s, 5 s and 10 s) and power function value (0.8, 1.0 and 1.2). The results showed that the
evaporation temperature had a positive impact on the signal-to-noise (S/N) ratios. On the other hand,
the peak area and the peak height decreased significantly upon raising the temperature. This finding
pointed out a strong need for fine tuning of mentioned parameter with respect to the analytes’
volatility. The increase in the value of the filter constant led to a baseline smoothing as well as peak
broadening. The filter constant set at 5 s resulted in the largest S/N ratios. The power function value,
which directly modified the CAD signal, exhibited an obvious negative effect toward the peak area. In
light of the above, optimal CAD detection of diclofenac, tramadol, potassium and chlorine was achieved
at the following settings: filter constant 5 s, power function value 0.8 and evaporation temperature
35ºC
AB  - S obzirom na veliku tržišnu zastupljenost farmaceutskih proizvoda koji sadrže kontra-
jone (50%), analiza istih ključna je komponenta procesa razvoja leka, kontrole kvaliteta i
puštanje serije leka u promet (1). Multimodalna hromatografija (eng. Mixed‐Mode
Chromatography, MMC) nudi moguć nost istovremene separacije katjonskih i anjonskih vrsta
na jednoj koloni, pojednostavljujući time laboratorijske procese (2). Međutim, izbor tehnika
za detekciju tipičnih kontra-jona veoma je sužen. Poslednjih godina, kontra-joni efikasno se
detektuju uz pomoć detektora naelektrisanja u aerosolu (eng. Charged Aerosol Detector,
CAD) koji generiše signal nezavisan od hemijske strukture (3). S navedenim u vezi, smatra se
da upotreba MMC-CAD tehnike racionalizuje broj pojedinačnih analitičkih aktivnosti
potrebnih za kontrolu kvaliteta analita i kontra-jona, smanjuje iscrpljivanje resursa i time
podržava koncept održivosti u domenu savremene analitike lekova. U ovom radu proučavan
je uticaj sistemskog variranja parametara CAD detektora na odgovor diklofenak-kalijuma i
tramadol-hidrohlorida. Hromatografkse analize izvedene su na Acclaim ™ Mixed‐mode WCX‐1
(2,1 x 150 nm, 3 μm) koloni koja kombinuje hidrofobne reverzno-fazne i mehanizme slabe
katjonske izmene. Zadovoljavajuće razdvajanje aktivnih farmaceutskih supstanci i njihovih
kontra-jona postignuto je upotrebom 90 mM acetatnog pufera pri pH 5 (A) i acetonitrila (B).
Korišćeno je izokratsko eluiranje mobilne faze (40% B), pri protoku od 0,4 mL/min. Na
osnovu preliminarnih eksperimenata, sledeć i faktori identifikovani su kao značajni, te su
testirani pri navedenim vrednostima: temperatura isparavanja (35ºC i 50ºC), konstanta
filtera (1 s, 5 s i 10 s) i vrednost stepene funkcije (0,8, 1,0 i 1,2). Rezultati su pokazali da je
temperatura isparavanja imala pozitivan efekat na odnos signal/šum (eng. signal‐to‐noise,
S/N). S druge strane, visina i površina pika značajno su se smanjili pri poveć anju
temperature. Ovaj nalaz ukazao je na snažnu potrebu za finim podešavanjem pomenutog
parametra imajući u vidu isparljivost analita. Poveć anje vrednosti konstante filtera dovelo je
do boljeg izgleda bazne linije, ali i do širenja pikova. Konstanta filtera postavljena na 5 s
rezultirala je najveć im vrednostima odnosa S/N. Vrednost stepene funkcije, koja je direktno
modifikovala CAD signal, pokazala je očigledan negativan efekat na površinu pika. U svetlu
eksperimentalnih nalaza, optimalna CAD detekcija diklofenaka, tramadola, kalijuma i hlora
postignuta je pri postavkama: konstanta filtera 5 s, vrednost funkcije snage 0,8 i temperatura
isparavanja 35ºC.
PB  - Savez farmaceutskih udruženja Srbije (SFUS)
C3  - Arhiv za farmaciju
T1  - Influence of charged aerosol detector parameters on the response of chosen analytes in the mixed‐mode chromatography system
T1  - Uticaj parametara detektora naelektirsanja u aerosolu na odgovore odabranih analita u sistemu multimodalne hromatografije
VL  - 71
IS  - 5 suplement
SP  - S122
EP  - S123
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4679
ER  - 

@conference{
author = "Krmar, Jovana and Svrkota, Bojana and Đajić, Nevena and Protić, Ana and Otašević, Biljana",
year = "2021",
abstract = "With respect to significant market presence (50%), the analysis of pharmaceuticals containing
counterions is a crucial component of the drug development life cycle, quality control and lot release
processes (1). Mixed-Mode Chromatography (MMC) offers the ability to simultaneously separate
cationic and anionic species within a single run, streamlining the laboratory processes (2). However,
the detection of typical counterions leaves analysts little room for maneuver. In recent years, the
counterions are efficiently detected with the help of Charged Aerosol Detector (CAD) that generates a
signal independent of the chemical structure (3). In this regard, the use of MMC-CAD hyphenated
technique rationalizes the number of individual analytical activities required for analyte and
counterion testing, causes no resource depletion and ultimately supports the concept of sustainability
in contemporary drug analysis. In this paper, the influence of the CAD parameters on the response of
diclofenac potassium and tramadol hydrochloride was studied performing systematic variations. The
analyses were carried out on Acclaim™ Mixed-mode WCX-1 (2.1 x 150 nm, 3 μm) column that provides
both hydrophobic reversed-phase and weak cation-exchange properties. Satisfactory separation of the
active pharmaceutical ingredients and their counterions was achieved using a mixture of 90 mM
acetate buffer at pH 5 (A) and acetonitrile (B). The isocratic elution (40% B) was performed at a flow
rate of 0.4 mL/min. Based on preliminary experiments, the following variables were identified as
significant and, thus, tested at the listed values: evaporation temperature (35ºC and 50ºC), filter
constant (1 s, 5 s and 10 s) and power function value (0.8, 1.0 and 1.2). The results showed that the
evaporation temperature had a positive impact on the signal-to-noise (S/N) ratios. On the other hand,
the peak area and the peak height decreased significantly upon raising the temperature. This finding
pointed out a strong need for fine tuning of mentioned parameter with respect to the analytes’
volatility. The increase in the value of the filter constant led to a baseline smoothing as well as peak
broadening. The filter constant set at 5 s resulted in the largest S/N ratios. The power function value,
which directly modified the CAD signal, exhibited an obvious negative effect toward the peak area. In
light of the above, optimal CAD detection of diclofenac, tramadol, potassium and chlorine was achieved
at the following settings: filter constant 5 s, power function value 0.8 and evaporation temperature
35ºC, S obzirom na veliku tržišnu zastupljenost farmaceutskih proizvoda koji sadrže kontra-
jone (50%), analiza istih ključna je komponenta procesa razvoja leka, kontrole kvaliteta i
puštanje serije leka u promet (1). Multimodalna hromatografija (eng. Mixed‐Mode
Chromatography, MMC) nudi moguć nost istovremene separacije katjonskih i anjonskih vrsta
na jednoj koloni, pojednostavljujući time laboratorijske procese (2). Međutim, izbor tehnika
za detekciju tipičnih kontra-jona veoma je sužen. Poslednjih godina, kontra-joni efikasno se
detektuju uz pomoć detektora naelektrisanja u aerosolu (eng. Charged Aerosol Detector,
CAD) koji generiše signal nezavisan od hemijske strukture (3). S navedenim u vezi, smatra se
da upotreba MMC-CAD tehnike racionalizuje broj pojedinačnih analitičkih aktivnosti
potrebnih za kontrolu kvaliteta analita i kontra-jona, smanjuje iscrpljivanje resursa i time
podržava koncept održivosti u domenu savremene analitike lekova. U ovom radu proučavan
je uticaj sistemskog variranja parametara CAD detektora na odgovor diklofenak-kalijuma i
tramadol-hidrohlorida. Hromatografkse analize izvedene su na Acclaim ™ Mixed‐mode WCX‐1
(2,1 x 150 nm, 3 μm) koloni koja kombinuje hidrofobne reverzno-fazne i mehanizme slabe
katjonske izmene. Zadovoljavajuće razdvajanje aktivnih farmaceutskih supstanci i njihovih
kontra-jona postignuto je upotrebom 90 mM acetatnog pufera pri pH 5 (A) i acetonitrila (B).
Korišćeno je izokratsko eluiranje mobilne faze (40% B), pri protoku od 0,4 mL/min. Na
osnovu preliminarnih eksperimenata, sledeć i faktori identifikovani su kao značajni, te su
testirani pri navedenim vrednostima: temperatura isparavanja (35ºC i 50ºC), konstanta
filtera (1 s, 5 s i 10 s) i vrednost stepene funkcije (0,8, 1,0 i 1,2). Rezultati su pokazali da je
temperatura isparavanja imala pozitivan efekat na odnos signal/šum (eng. signal‐to‐noise,
S/N). S druge strane, visina i površina pika značajno su se smanjili pri poveć anju
temperature. Ovaj nalaz ukazao je na snažnu potrebu za finim podešavanjem pomenutog
parametra imajući u vidu isparljivost analita. Poveć anje vrednosti konstante filtera dovelo je
do boljeg izgleda bazne linije, ali i do širenja pikova. Konstanta filtera postavljena na 5 s
rezultirala je najveć im vrednostima odnosa S/N. Vrednost stepene funkcije, koja je direktno
modifikovala CAD signal, pokazala je očigledan negativan efekat na površinu pika. U svetlu
eksperimentalnih nalaza, optimalna CAD detekcija diklofenaka, tramadola, kalijuma i hlora
postignuta je pri postavkama: konstanta filtera 5 s, vrednost funkcije snage 0,8 i temperatura
isparavanja 35ºC.",
publisher = "Savez farmaceutskih udruženja Srbije (SFUS)",
journal = "Arhiv za farmaciju",
title = "Influence of charged aerosol detector parameters on the response of chosen analytes in the mixed‐mode chromatography system, Uticaj parametara detektora naelektirsanja u aerosolu na odgovore odabranih analita u sistemu multimodalne hromatografije",
volume = "71",
number = "5 suplement",
pages = "S122-S123",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4679"
}

Krmar, J., Svrkota, B., Đajić, N., Protić, A.,& Otašević, B.. (2021). Influence of charged aerosol detector parameters on the response of chosen analytes in the mixed‐mode chromatography system. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije (SFUS)., 71(5 suplement), S122-S123.
https://hdl.handle.net/21.15107/rcub_farfar_4679

Krmar J, Svrkota B, Đajić N, Protić A, Otašević B. Influence of charged aerosol detector parameters on the response of chosen analytes in the mixed‐mode chromatography system. in Arhiv za farmaciju. 2021;71(5 suplement):S122-S123.
https://hdl.handle.net/21.15107/rcub_farfar_4679 .

Krmar, Jovana, Svrkota, Bojana, Đajić, Nevena, Protić, Ana, Otašević, Biljana, "Influence of charged aerosol detector parameters on the response of chosen analytes in the mixed‐mode chromatography system" in Arhiv za farmaciju, 71, no. 5 suplement (2021):S122-S123,
https://hdl.handle.net/21.15107/rcub_farfar_4679 .

TY  - CONF
AU  - Otašević, Biljana
AU  - Đajić, Nevena
AU  - Golubović, Jelena
AU  - Krmar, Jovana
AU  - Protić, Ana
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/4667
AB  - Qualitative and quantitative assessment of drug substances and drug dosage forms is of utmost
importance for the quality control in pharmaceutical industry. Among the analytical techniques
available, high performance liquid chromatography (HPLC) stands out due to its high efficiency and
robustness. But, HPLC is also characterized by high consumption of toxic organic solvents used both for
method development and routine analyses. These solvents could harmfully impact the environment
and human health. Therefore, various strategies are developing for attracting eco-friendly character to
HPLC. Recently introduced green chromatography concept is based on the 3R rule (Reduce – Replace –
Recycle) implying the HPLC method development governed by the decreased use of acetonitrile labeled
as the most commonly used HPLC solvent and its replacement with ethanol or acetone (1). However,
these greener alternatives are known for their high UV absorbtion cut-off values making them
unsuitable for common UV/VIS detection. As appropriate solvent compatible solution, the use of
Corona Charged Aerosol Detector (CAD) is proposed. CAD is recognized as a universal detector
providing persistent mass sensitive analyte response independent of chemical structure (no need for
UV/VIS chromofores or ionization ability). The detection principle involves the nebulization of
chromatographic mobile phase, the evaporation of aerosol droplets and finally the production of
charged analyte particles (2). Assuming that chromatographic behavior and CAD generated responses
of analytes could be affected by various mobile phase related factors and/or detector parameters
settings, design of experiments (DoE) supported HPLC-CAD method development was performed for
the analysis of antipsychotic drug risperidone in presence of its impurities. By carefully planning the
number and the order of performing experiments, DoE methodology enables investigation of
significance effects of multiple factor effects together with their factor interactions. Different
experimental settings involving variation of organic solvent type and content in range 15-25% (V/V),
mobile phase flow rate (0.50-1.00 mL min -1) and column temperature (25-50 °C) were examined in
accordance with Box-Behnken design and selectivity factor between adjacent peaks on the
chromatogram was measured. The optimal conditions were defined applying mucticriteria decision
making approach by means of Derringer desirability function evaluation. Optimal separations were
achieved using 20% (V/V) of ethanol in mobile phase flowing at 0.6 mL min -1 under 37.5 °C column
temperature, while in case of acetone, optimum comprised 17% (V/V) of organic modifier, 0.8 mL min -1
and 37.5 °C. Finally, eco-friendly character of both methods was rated by Green Analytical Procedure
Index, GAPI (3).
AB  - Kvalitativna i kvantitativna analiza farmaceutskih supstanci i doziranih oblika predstavlja
činioce od najvećeg značaja za kontrolu kvaliteta u farmaceutskoj industriji. Među dostupnim
analitičkim tehnikama, tečna hromatografija pod visokim pritiskom (HPLC) ističe se svojom visokom
efikasnošć u i robusnošću. Ali, HPLC takođe karakteriše velika potrošnja toksičnih organskih rastvarača
koji se koriste za razvoj metoda i za rutinsku analizu lekova. Ovi rastvarači mogu štetno uticati i na
životnu sredinu i na zdravlje ljudi. Zbog toga se razvijaju različite strategije za obezbeđivanje ekološki
prihvatljivog karaktera HPLC metode. Nedavno predstavljeni koncept zelene hromatografije zasnovan
je na pravilu 3 R (Smanji - Zameni - Recikliraj), što podrazumeva razvoj HPLC metode koji se rukovodi
smanjenom upotrebom acetonitrila kao najčešće korišć enog rastvarača i njegovu zamenu etanolom ili
acetonom (1). Međutim, ove zelenije alternative poznate su po visokim vrednostima za UV apsorpciju,
što ih čini neprikladnim za uobičajenu UV/VIS detekciju. Kao odgovarajuće rešenje kompatibilno sa
pomenutim rastvaračima, predlaže se upotreba detektora naelektrisanja u aerosolu (CAD). CAD je
prepoznat kao univerzalni detektor koji pruža postojan odgovor zavistan od mase analita, a nezavisan
od hemijske strukture (postojanje UV/VIS hromofora ili sposobnosti jonizacije). Princip CAD detekcije
uključuje raspršivanje hromatografske mobilne faze u vidu kapljica aerosola, njihovo isparavanje i
konačno naelektrisavanje dobijenih čestica analita (2). Pretpostavljajuć i da na hromatografsko
ponašanje i CAD generisane odgovore analita mogu uticati različiti faktori povezani sa mobilnom fazom
i/ili parametrima podešavanja detektora, izvršen je razvoj HPLC-CAD metode za analizu antipsihotika
risperidona u prisustvu njegovih nečistoća uz podršku metodologije dizajna eksperimenata (DoE).
Pažljivim planiranjem broja i redosleda izvođenja eksperimenata, DoE omoguć ava ispitivanje značaja
efekata više faktora istovremeno zajedno sa njihovim faktorskim interakcijama. Različite
eksperimentalne postavke koje uključuju varijacije tipa i sadržaja organskog rastvarača u opsegu 15-
25% (V/V), protok mobilne faze (0,50-1,00 mL min -1) i temperaturu kolone (25-50 °C) ispitivane su u
skladu sa Boks-Behnken-ovim dizajnom i faktor selektivnosti između susednih vrhova na
hromatogramu je praćen. Optimalni uslovi definisani su primenom pristupa mutikriterijumskog
odlučivanja baziranog na izračunavanju Derringer-ove funkcije poželjnosti. Optimalna separacija je
postignuta primenom 20% (V/V) etanola u mobilnoj fazi koja teče pri 0,6 mL min -1 i pri temperaturi
kolone od 37,5 °C, dok je u slučaju acetona optimum podrazumevao 17% (V/V) organskog
modifikatora, protok 0,8 mL min -1 i temperaturu 37,5 °C. Konačno, ekološki karakter obe metode
procenjen je na osnovu indeksa zelenih analitičkih procedura, GAPI (3).
PB  - Savez farmaceutskih udruženja Srbije (SFUS)
C3  - Arhiv za farmaciju
T1  - New strategies in the development of ecologically friendly RP‐HPLC methods based on the charged aerosol detector
T1  - Nove strategije u razvoju ekološki prihvatljivih RP‐HPLC metoda primenom detektora naelektrisanja u aerosolu
VL  - 71
IS  - 5 suplement
SP  - S24
EP  - S25
UR  - https://hdl.handle.net/21.15107/rcub_farfar_4667
ER  - 

@conference{
author = "Otašević, Biljana and Đajić, Nevena and Golubović, Jelena and Krmar, Jovana and Protić, Ana",
year = "2021",
abstract = "Qualitative and quantitative assessment of drug substances and drug dosage forms is of utmost
importance for the quality control in pharmaceutical industry. Among the analytical techniques
available, high performance liquid chromatography (HPLC) stands out due to its high efficiency and
robustness. But, HPLC is also characterized by high consumption of toxic organic solvents used both for
method development and routine analyses. These solvents could harmfully impact the environment
and human health. Therefore, various strategies are developing for attracting eco-friendly character to
HPLC. Recently introduced green chromatography concept is based on the 3R rule (Reduce – Replace –
Recycle) implying the HPLC method development governed by the decreased use of acetonitrile labeled
as the most commonly used HPLC solvent and its replacement with ethanol or acetone (1). However,
these greener alternatives are known for their high UV absorbtion cut-off values making them
unsuitable for common UV/VIS detection. As appropriate solvent compatible solution, the use of
Corona Charged Aerosol Detector (CAD) is proposed. CAD is recognized as a universal detector
providing persistent mass sensitive analyte response independent of chemical structure (no need for
UV/VIS chromofores or ionization ability). The detection principle involves the nebulization of
chromatographic mobile phase, the evaporation of aerosol droplets and finally the production of
charged analyte particles (2). Assuming that chromatographic behavior and CAD generated responses
of analytes could be affected by various mobile phase related factors and/or detector parameters
settings, design of experiments (DoE) supported HPLC-CAD method development was performed for
the analysis of antipsychotic drug risperidone in presence of its impurities. By carefully planning the
number and the order of performing experiments, DoE methodology enables investigation of
significance effects of multiple factor effects together with their factor interactions. Different
experimental settings involving variation of organic solvent type and content in range 15-25% (V/V),
mobile phase flow rate (0.50-1.00 mL min -1) and column temperature (25-50 °C) were examined in
accordance with Box-Behnken design and selectivity factor between adjacent peaks on the
chromatogram was measured. The optimal conditions were defined applying mucticriteria decision
making approach by means of Derringer desirability function evaluation. Optimal separations were
achieved using 20% (V/V) of ethanol in mobile phase flowing at 0.6 mL min -1 under 37.5 °C column
temperature, while in case of acetone, optimum comprised 17% (V/V) of organic modifier, 0.8 mL min -1
and 37.5 °C. Finally, eco-friendly character of both methods was rated by Green Analytical Procedure
Index, GAPI (3)., Kvalitativna i kvantitativna analiza farmaceutskih supstanci i doziranih oblika predstavlja
činioce od najvećeg značaja za kontrolu kvaliteta u farmaceutskoj industriji. Među dostupnim
analitičkim tehnikama, tečna hromatografija pod visokim pritiskom (HPLC) ističe se svojom visokom
efikasnošć u i robusnošću. Ali, HPLC takođe karakteriše velika potrošnja toksičnih organskih rastvarača
koji se koriste za razvoj metoda i za rutinsku analizu lekova. Ovi rastvarači mogu štetno uticati i na
životnu sredinu i na zdravlje ljudi. Zbog toga se razvijaju različite strategije za obezbeđivanje ekološki
prihvatljivog karaktera HPLC metode. Nedavno predstavljeni koncept zelene hromatografije zasnovan
je na pravilu 3 R (Smanji - Zameni - Recikliraj), što podrazumeva razvoj HPLC metode koji se rukovodi
smanjenom upotrebom acetonitrila kao najčešće korišć enog rastvarača i njegovu zamenu etanolom ili
acetonom (1). Međutim, ove zelenije alternative poznate su po visokim vrednostima za UV apsorpciju,
što ih čini neprikladnim za uobičajenu UV/VIS detekciju. Kao odgovarajuće rešenje kompatibilno sa
pomenutim rastvaračima, predlaže se upotreba detektora naelektrisanja u aerosolu (CAD). CAD je
prepoznat kao univerzalni detektor koji pruža postojan odgovor zavistan od mase analita, a nezavisan
od hemijske strukture (postojanje UV/VIS hromofora ili sposobnosti jonizacije). Princip CAD detekcije
uključuje raspršivanje hromatografske mobilne faze u vidu kapljica aerosola, njihovo isparavanje i
konačno naelektrisavanje dobijenih čestica analita (2). Pretpostavljajuć i da na hromatografsko
ponašanje i CAD generisane odgovore analita mogu uticati različiti faktori povezani sa mobilnom fazom
i/ili parametrima podešavanja detektora, izvršen je razvoj HPLC-CAD metode za analizu antipsihotika
risperidona u prisustvu njegovih nečistoća uz podršku metodologije dizajna eksperimenata (DoE).
Pažljivim planiranjem broja i redosleda izvođenja eksperimenata, DoE omoguć ava ispitivanje značaja
efekata više faktora istovremeno zajedno sa njihovim faktorskim interakcijama. Različite
eksperimentalne postavke koje uključuju varijacije tipa i sadržaja organskog rastvarača u opsegu 15-
25% (V/V), protok mobilne faze (0,50-1,00 mL min -1) i temperaturu kolone (25-50 °C) ispitivane su u
skladu sa Boks-Behnken-ovim dizajnom i faktor selektivnosti između susednih vrhova na
hromatogramu je praćen. Optimalni uslovi definisani su primenom pristupa mutikriterijumskog
odlučivanja baziranog na izračunavanju Derringer-ove funkcije poželjnosti. Optimalna separacija je
postignuta primenom 20% (V/V) etanola u mobilnoj fazi koja teče pri 0,6 mL min -1 i pri temperaturi
kolone od 37,5 °C, dok je u slučaju acetona optimum podrazumevao 17% (V/V) organskog
modifikatora, protok 0,8 mL min -1 i temperaturu 37,5 °C. Konačno, ekološki karakter obe metode
procenjen je na osnovu indeksa zelenih analitičkih procedura, GAPI (3).",
publisher = "Savez farmaceutskih udruženja Srbije (SFUS)",
journal = "Arhiv za farmaciju",
title = "New strategies in the development of ecologically friendly RP‐HPLC methods based on the charged aerosol detector, Nove strategije u razvoju ekološki prihvatljivih RP‐HPLC metoda primenom detektora naelektrisanja u aerosolu",
volume = "71",
number = "5 suplement",
pages = "S24-S25",
url = "https://hdl.handle.net/21.15107/rcub_farfar_4667"
}

Otašević, B., Đajić, N., Golubović, J., Krmar, J.,& Protić, A.. (2021). New strategies in the development of ecologically friendly RP‐HPLC methods based on the charged aerosol detector. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije (SFUS)., 71(5 suplement), S24-S25.
https://hdl.handle.net/21.15107/rcub_farfar_4667

Otašević B, Đajić N, Golubović J, Krmar J, Protić A. New strategies in the development of ecologically friendly RP‐HPLC methods based on the charged aerosol detector. in Arhiv za farmaciju. 2021;71(5 suplement):S24-S25.
https://hdl.handle.net/21.15107/rcub_farfar_4667 .

Otašević, Biljana, Đajić, Nevena, Golubović, Jelena, Krmar, Jovana, Protić, Ana, "New strategies in the development of ecologically friendly RP‐HPLC methods based on the charged aerosol detector" in Arhiv za farmaciju, 71, no. 5 suplement (2021):S24-S25,
https://hdl.handle.net/21.15107/rcub_farfar_4667 .

TY  - JOUR
AU  - Pawellek, Ruben
AU  - Krmar, Jovana
AU  - Leistner, Adrian
AU  - Đajić, Nevena
AU  - Otašević, Biljana
AU  - Protić, Ana
AU  - Holzgrabe, Ulrike
PY  - 2021
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3926
AB  - The charged aerosol detector (CAD) is the latest representative of aerosol-based detectors that generate a response  independent of the analytes’ chemical structure. This study was aimed at accurately predicting the CAD response  of homologous fatty acids under varying experimental conditions. Fatty acids from C12 to C18 were used as model  substances due to semivolatile characterics that caused non-uniform CAD behaviour. Considering both experimental  conditions and molecular descriptors, a mixed quantitative structure–property relationship (QSPR) modeling was  performed using Gradient Boosted Trees (GBT ). The ensemble of 10 decisions trees (learning rate set at 0.55, the  maximal depth set at 5, and the sample rate set at 1.0) was able to explain approximately 99%  (Q2: 0.987, RMSE: 0.051)  of the observed variance in CAD responses. Validation using an external test compound confirmed the high predic- tive ability of the model established  (R2: 0.990, RMSEP: 0.050). With respect to the intrinsic attribute selection strategy,  GBT used almost all independent variables during model building. Finally, it attributed the highest importance to  the power function value, the flow rate of the mobile phase, evaporation temperature, the content of the organic  solvent in the mobile phase and the molecular descriptors such as molecular weight (MW ), Radial Distribution Func- tion—080/weighted by mass (RDF080m) and average coefficient of the last eigenvector from distance/detour matrix  (Ve2_D/Dt). The identification of the factors most relevant to the CAD responsiveness has contributed to a better  understanding of the underlying mechanisms of signal generation. An increased CAD response that was obtained for  acetone as organic modifier demonstrated its potential to replace the more expensive and environmentally harmful  acetonitrile.
PB  - BioMed Central Ltd
T2  - Journal of Cheminformatics
T1  - Charged aerosol detector response modeling for fatty acids based on experimental settings and molecular features: a machine learning approach
VL  - 13
IS  - 1
DO  - 10.1186/s13321-021-00532-0
ER  - 

@article{
author = "Pawellek, Ruben and Krmar, Jovana and Leistner, Adrian and Đajić, Nevena and Otašević, Biljana and Protić, Ana and Holzgrabe, Ulrike",
year = "2021",
abstract = "The charged aerosol detector (CAD) is the latest representative of aerosol-based detectors that generate a response  independent of the analytes’ chemical structure. This study was aimed at accurately predicting the CAD response  of homologous fatty acids under varying experimental conditions. Fatty acids from C12 to C18 were used as model  substances due to semivolatile characterics that caused non-uniform CAD behaviour. Considering both experimental  conditions and molecular descriptors, a mixed quantitative structure–property relationship (QSPR) modeling was  performed using Gradient Boosted Trees (GBT ). The ensemble of 10 decisions trees (learning rate set at 0.55, the  maximal depth set at 5, and the sample rate set at 1.0) was able to explain approximately 99%  (Q2: 0.987, RMSE: 0.051)  of the observed variance in CAD responses. Validation using an external test compound confirmed the high predic- tive ability of the model established  (R2: 0.990, RMSEP: 0.050). With respect to the intrinsic attribute selection strategy,  GBT used almost all independent variables during model building. Finally, it attributed the highest importance to  the power function value, the flow rate of the mobile phase, evaporation temperature, the content of the organic  solvent in the mobile phase and the molecular descriptors such as molecular weight (MW ), Radial Distribution Func- tion—080/weighted by mass (RDF080m) and average coefficient of the last eigenvector from distance/detour matrix  (Ve2_D/Dt). The identification of the factors most relevant to the CAD responsiveness has contributed to a better  understanding of the underlying mechanisms of signal generation. An increased CAD response that was obtained for  acetone as organic modifier demonstrated its potential to replace the more expensive and environmentally harmful  acetonitrile.",
publisher = "BioMed Central Ltd",
journal = "Journal of Cheminformatics",
title = "Charged aerosol detector response modeling for fatty acids based on experimental settings and molecular features: a machine learning approach",
volume = "13",
number = "1",
doi = "10.1186/s13321-021-00532-0"
}

Pawellek, R., Krmar, J., Leistner, A., Đajić, N., Otašević, B., Protić, A.,& Holzgrabe, U.. (2021). Charged aerosol detector response modeling for fatty acids based on experimental settings and molecular features: a machine learning approach. in Journal of Cheminformatics
BioMed Central Ltd., 13(1).
https://doi.org/10.1186/s13321-021-00532-0

Pawellek R, Krmar J, Leistner A, Đajić N, Otašević B, Protić A, Holzgrabe U. Charged aerosol detector response modeling for fatty acids based on experimental settings and molecular features: a machine learning approach. in Journal of Cheminformatics. 2021;13(1).
doi:10.1186/s13321-021-00532-0 .

Pawellek, Ruben, Krmar, Jovana, Leistner, Adrian, Đajić, Nevena, Otašević, Biljana, Protić, Ana, Holzgrabe, Ulrike, "Charged aerosol detector response modeling for fatty acids based on experimental settings and molecular features: a machine learning approach" in Journal of Cheminformatics, 13, no. 1 (2021),
https://doi.org/10.1186/s13321-021-00532-0 . .