TY  - JOUR
AU  - Stajić, Ana
AU  - Maksić, Jelena
AU  - Maksić, Đoko
AU  - Forsdahl, Guro
AU  - Medenica, Mirjana
AU  - Jančić-Stojanović, Biljana
PY  - 2018
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3080
AB  - Aim: An ultra pressure liquid chromatography (UPLC)/MS/MS method for vancomycin and teicoplanin determination in human plasma was developed in accordance with analytical quality by design (AQbD) concept and fully validated. Materials & methods: Chromatographic separation was performed on ACQUITY UPLC C-18 charge surface hybrid (CSH) column (2.1 mm x 50 mm, 1.7 mu m particle size) in gradient mode and the mobile phase consisted of 0.1% formic acid in water and pure acetonitrile. The experimental design methodology was used for the definition of optimal chromatographic and protein precipitation conditions. Results: The linearity ranges were 0.05-10 mu g ml(-1) for vancomycin and 0.5-200 mu g ml(-1) for total teicoplanin. The relative standard deviations for precision estimation were below 15% and the accuracy was within 85-115% for all quality control levels. Conclusion: The method was utilized for glycopeptide antibiotics bioanalysis.
PB  - Future Sci Ltd, London
T2  - Bioanalysis
T1  - Analytical Quality by Design-based development and validation of ultra pressure liquid chromatography/MS/MS method for glycopeptide antibiotics determination in human plasma
VL  - 10
IS  - 22
SP  - 1861
EP  - 1876
DO  - 10.4155/bio-2018-0181
ER  - 

@article{
author = "Stajić, Ana and Maksić, Jelena and Maksić, Đoko and Forsdahl, Guro and Medenica, Mirjana and Jančić-Stojanović, Biljana",
year = "2018",
abstract = "Aim: An ultra pressure liquid chromatography (UPLC)/MS/MS method for vancomycin and teicoplanin determination in human plasma was developed in accordance with analytical quality by design (AQbD) concept and fully validated. Materials & methods: Chromatographic separation was performed on ACQUITY UPLC C-18 charge surface hybrid (CSH) column (2.1 mm x 50 mm, 1.7 mu m particle size) in gradient mode and the mobile phase consisted of 0.1% formic acid in water and pure acetonitrile. The experimental design methodology was used for the definition of optimal chromatographic and protein precipitation conditions. Results: The linearity ranges were 0.05-10 mu g ml(-1) for vancomycin and 0.5-200 mu g ml(-1) for total teicoplanin. The relative standard deviations for precision estimation were below 15% and the accuracy was within 85-115% for all quality control levels. Conclusion: The method was utilized for glycopeptide antibiotics bioanalysis.",
publisher = "Future Sci Ltd, London",
journal = "Bioanalysis",
title = "Analytical Quality by Design-based development and validation of ultra pressure liquid chromatography/MS/MS method for glycopeptide antibiotics determination in human plasma",
volume = "10",
number = "22",
pages = "1861-1876",
doi = "10.4155/bio-2018-0181"
}

Stajić, A., Maksić, J., Maksić, Đ., Forsdahl, G., Medenica, M.,& Jančić-Stojanović, B.. (2018). Analytical Quality by Design-based development and validation of ultra pressure liquid chromatography/MS/MS method for glycopeptide antibiotics determination in human plasma. in Bioanalysis
Future Sci Ltd, London., 10(22), 1861-1876.
https://doi.org/10.4155/bio-2018-0181

Stajić A, Maksić J, Maksić Đ, Forsdahl G, Medenica M, Jančić-Stojanović B. Analytical Quality by Design-based development and validation of ultra pressure liquid chromatography/MS/MS method for glycopeptide antibiotics determination in human plasma. in Bioanalysis. 2018;10(22):1861-1876.
doi:10.4155/bio-2018-0181 .

Stajić, Ana, Maksić, Jelena, Maksić, Đoko, Forsdahl, Guro, Medenica, Mirjana, Jančić-Stojanović, Biljana, "Analytical Quality by Design-based development and validation of ultra pressure liquid chromatography/MS/MS method for glycopeptide antibiotics determination in human plasma" in Bioanalysis, 10, no. 22 (2018):1861-1876,
https://doi.org/10.4155/bio-2018-0181 . .

TY  - JOUR
AU  - Tumpa, Anja
AU  - Stajić, Ana
AU  - Jančić-Stojanović, Biljana
AU  - Medenica, Mirjana
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2958
AB  - This paper deals with the development of hydrophilic interaction liquid chromatography (HILIC) method with gradient elution, in accordance with Analytical Quality by Design (AQbD) methodology, for the first time. The method is developed for olanzapine and its seven related substances. Following step by step AQbD methodology, firstly as critical process parameters (CPPs) temperature, starting content of aqueous phase and duration of linear gradient are recognized, and as critical quality attributes (CQAs) separation criterion S of critical pairs of substances are investigated. Rechtschaffen design is used for the creation of models that describe the dependence between CPPs and CQAs. The design space that is obtained at the end is used for choosing the optimal conditions (set point). The method is fully validated at the end to verify the adequacy of the chosen optimal conditions and applied to real samples.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Quality by Design in the development of hydrophilic interaction liquid chromatography method with gradient elution for the analysis of olanzapine
VL  - 134
SP  - 18
EP  - 26
DO  - 10.1016/j.jpba.2016.11.010
ER  - 

@article{
author = "Tumpa, Anja and Stajić, Ana and Jančić-Stojanović, Biljana and Medenica, Mirjana",
year = "2017",
abstract = "This paper deals with the development of hydrophilic interaction liquid chromatography (HILIC) method with gradient elution, in accordance with Analytical Quality by Design (AQbD) methodology, for the first time. The method is developed for olanzapine and its seven related substances. Following step by step AQbD methodology, firstly as critical process parameters (CPPs) temperature, starting content of aqueous phase and duration of linear gradient are recognized, and as critical quality attributes (CQAs) separation criterion S of critical pairs of substances are investigated. Rechtschaffen design is used for the creation of models that describe the dependence between CPPs and CQAs. The design space that is obtained at the end is used for choosing the optimal conditions (set point). The method is fully validated at the end to verify the adequacy of the chosen optimal conditions and applied to real samples.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Quality by Design in the development of hydrophilic interaction liquid chromatography method with gradient elution for the analysis of olanzapine",
volume = "134",
pages = "18-26",
doi = "10.1016/j.jpba.2016.11.010"
}

Tumpa, A., Stajić, A., Jančić-Stojanović, B.,& Medenica, M.. (2017). Quality by Design in the development of hydrophilic interaction liquid chromatography method with gradient elution for the analysis of olanzapine. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 134, 18-26.
https://doi.org/10.1016/j.jpba.2016.11.010

Tumpa A, Stajić A, Jančić-Stojanović B, Medenica M. Quality by Design in the development of hydrophilic interaction liquid chromatography method with gradient elution for the analysis of olanzapine. in Journal of Pharmaceutical and Biomedical Analysis. 2017;134:18-26.
doi:10.1016/j.jpba.2016.11.010 .

Tumpa, Anja, Stajić, Ana, Jančić-Stojanović, Biljana, Medenica, Mirjana, "Quality by Design in the development of hydrophilic interaction liquid chromatography method with gradient elution for the analysis of olanzapine" in Journal of Pharmaceutical and Biomedical Analysis, 134 (2017):18-26,
https://doi.org/10.1016/j.jpba.2016.11.010 . .

TY  - JOUR
AU  - Maksić, Jelena
AU  - Stajić, Ana
AU  - Knežević, Miroslav
AU  - Dacić-Krnjaja, Bojana
AU  - Jančić-Stojanović, Biljana
AU  - Medenica, Mirjana
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2860
AB  - Aim: The objective of the study was development of hydrophilic interaction liquid chromatography-ESI/MS/MS method for the determination of olopatadine in tear matrix. Materials & methods: Separation was performed on Acquity BEH amide column (2.1 x 100 mm, 1.7 mu m). The mobile phase was consisted of 0.1% formic acid in water and acetonitrile. Mianserin hydrochloride was implemented as an internal standard. The artificial tear fluid was used as matrix. The tear samples were collected using Schirmer test strips. For the optimization of ultra pressure liquid chromatography conditions, Box-Benhken design was utilized. Results: The optimal values of the ion source and collision cell parameters were found. Quantification was performed in multiple reaction monitoring mode. The optimized method was fully validated. Conclusion: The proposed method was utilized for monitoring of olopatadine in human tear.
PB  - Future Sci Ltd, London
T2  - Bioanalysis
T1  - Determination of olopatadine in human tears by hydrophilic interaction liquid chromatography-MS/MS method
VL  - 9
IS  - 24
SP  - 1943
EP  - 1954
DO  - 10.4155/bio-2017-0172
ER  - 

@article{
author = "Maksić, Jelena and Stajić, Ana and Knežević, Miroslav and Dacić-Krnjaja, Bojana and Jančić-Stojanović, Biljana and Medenica, Mirjana",
year = "2017",
abstract = "Aim: The objective of the study was development of hydrophilic interaction liquid chromatography-ESI/MS/MS method for the determination of olopatadine in tear matrix. Materials & methods: Separation was performed on Acquity BEH amide column (2.1 x 100 mm, 1.7 mu m). The mobile phase was consisted of 0.1% formic acid in water and acetonitrile. Mianserin hydrochloride was implemented as an internal standard. The artificial tear fluid was used as matrix. The tear samples were collected using Schirmer test strips. For the optimization of ultra pressure liquid chromatography conditions, Box-Benhken design was utilized. Results: The optimal values of the ion source and collision cell parameters were found. Quantification was performed in multiple reaction monitoring mode. The optimized method was fully validated. Conclusion: The proposed method was utilized for monitoring of olopatadine in human tear.",
publisher = "Future Sci Ltd, London",
journal = "Bioanalysis",
title = "Determination of olopatadine in human tears by hydrophilic interaction liquid chromatography-MS/MS method",
volume = "9",
number = "24",
pages = "1943-1954",
doi = "10.4155/bio-2017-0172"
}

Maksić, J., Stajić, A., Knežević, M., Dacić-Krnjaja, B., Jančić-Stojanović, B.,& Medenica, M.. (2017). Determination of olopatadine in human tears by hydrophilic interaction liquid chromatography-MS/MS method. in Bioanalysis
Future Sci Ltd, London., 9(24), 1943-1954.
https://doi.org/10.4155/bio-2017-0172

Maksić J, Stajić A, Knežević M, Dacić-Krnjaja B, Jančić-Stojanović B, Medenica M. Determination of olopatadine in human tears by hydrophilic interaction liquid chromatography-MS/MS method. in Bioanalysis. 2017;9(24):1943-1954.
doi:10.4155/bio-2017-0172 .

Maksić, Jelena, Stajić, Ana, Knežević, Miroslav, Dacić-Krnjaja, Bojana, Jančić-Stojanović, Biljana, Medenica, Mirjana, "Determination of olopatadine in human tears by hydrophilic interaction liquid chromatography-MS/MS method" in Bioanalysis, 9, no. 24 (2017):1943-1954,
https://doi.org/10.4155/bio-2017-0172 . .

TY  - JOUR
AU  - Tumpa, Anja
AU  - Misković, Stefan
AU  - Stanimirović, Zorica
AU  - Jančić-Stojanović, Biljana
AU  - Medenica, Mirjana
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2792
AB  - When it is taken into account that hydrophilic interaction liquid chromatography (HILIC) as an analytical method is relatively young compared with the other techniques, retention modeling could still bring scientifically valuable data to the field. Therefore, in this paper, olanzapine and its 8 impurities were selected as a test mixture, considering that they have never been analyzed in HILIC before. Their investigation on 4 different HILIC columns (bare silica, cyanopropyl, diol and zwitterionic) has been performed. The mixture of 9 structurally similar substances allows the examination of complex HILIC retention behavior depending on the chemical properties of the analytes, as well as of the stationary phase. To describe the nature of the relationship between the retention and the stronger eluent content in the mobile phase, we fitted experimentally obtained data to several theoretical (localized adsorption, nonlocalized partition, quadratic, and mixed) models. Results show that the best fit is the quadratic model with the highest R-2 and cross-validated coefficient of determination (Q(2)) values, but its usage has some drawbacks. With the aim to improve the possibility to predict retention behavior in HILIC, a new empirical model was proposed. For that purpose, a spline interpolation technique was performed, by dividing the experimental range into several subdivisions. This type of interpolation was performed for the first time in the chromatographic field. The estimation of the polynomial equations was performed using Q(2) values. Obtained Q(2) values pointed out the goodness of fit of the model, as well as its good predictive capabilities. In the end, the prediction capabilities were experimentally verified, under randomly chosen conditions from the experimental range. The errors in prediction were all under 10%, which is satisfying for HILIC. In this paper, retention behavior of olanzapine and its 8 impurities was investigated on four HILIC columns (bare silica, cyanopropyl, diol, and zwitterionic). Experimentally obtained data were fitted to several theoretical (localized adsorption, nonlocalized partition, quadratic, and mixed) models. Furthermore, a new empirical model (spline interpolation) was proposed. This type of interpolation was performed for the first time in the chromatography. Obtained Q(2) values pointed out the goodness of fit of the model, as well as its good predictive capabilities.
PB  - Wiley, Hoboken
T2  - Journal of Chemometrics
T1  - Modeling of HILIC retention behavior with theoretical models and new spline interpolation technique
VL  - 31
IS  - 9
DO  - 10.1002/cem.2910
ER  - 

@article{
author = "Tumpa, Anja and Misković, Stefan and Stanimirović, Zorica and Jančić-Stojanović, Biljana and Medenica, Mirjana",
year = "2017",
abstract = "When it is taken into account that hydrophilic interaction liquid chromatography (HILIC) as an analytical method is relatively young compared with the other techniques, retention modeling could still bring scientifically valuable data to the field. Therefore, in this paper, olanzapine and its 8 impurities were selected as a test mixture, considering that they have never been analyzed in HILIC before. Their investigation on 4 different HILIC columns (bare silica, cyanopropyl, diol and zwitterionic) has been performed. The mixture of 9 structurally similar substances allows the examination of complex HILIC retention behavior depending on the chemical properties of the analytes, as well as of the stationary phase. To describe the nature of the relationship between the retention and the stronger eluent content in the mobile phase, we fitted experimentally obtained data to several theoretical (localized adsorption, nonlocalized partition, quadratic, and mixed) models. Results show that the best fit is the quadratic model with the highest R-2 and cross-validated coefficient of determination (Q(2)) values, but its usage has some drawbacks. With the aim to improve the possibility to predict retention behavior in HILIC, a new empirical model was proposed. For that purpose, a spline interpolation technique was performed, by dividing the experimental range into several subdivisions. This type of interpolation was performed for the first time in the chromatographic field. The estimation of the polynomial equations was performed using Q(2) values. Obtained Q(2) values pointed out the goodness of fit of the model, as well as its good predictive capabilities. In the end, the prediction capabilities were experimentally verified, under randomly chosen conditions from the experimental range. The errors in prediction were all under 10%, which is satisfying for HILIC. In this paper, retention behavior of olanzapine and its 8 impurities was investigated on four HILIC columns (bare silica, cyanopropyl, diol, and zwitterionic). Experimentally obtained data were fitted to several theoretical (localized adsorption, nonlocalized partition, quadratic, and mixed) models. Furthermore, a new empirical model (spline interpolation) was proposed. This type of interpolation was performed for the first time in the chromatography. Obtained Q(2) values pointed out the goodness of fit of the model, as well as its good predictive capabilities.",
publisher = "Wiley, Hoboken",
journal = "Journal of Chemometrics",
title = "Modeling of HILIC retention behavior with theoretical models and new spline interpolation technique",
volume = "31",
number = "9",
doi = "10.1002/cem.2910"
}

Tumpa, A., Misković, S., Stanimirović, Z., Jančić-Stojanović, B.,& Medenica, M.. (2017). Modeling of HILIC retention behavior with theoretical models and new spline interpolation technique. in Journal of Chemometrics
Wiley, Hoboken., 31(9).
https://doi.org/10.1002/cem.2910

Tumpa A, Misković S, Stanimirović Z, Jančić-Stojanović B, Medenica M. Modeling of HILIC retention behavior with theoretical models and new spline interpolation technique. in Journal of Chemometrics. 2017;31(9).
doi:10.1002/cem.2910 .

Tumpa, Anja, Misković, Stefan, Stanimirović, Zorica, Jančić-Stojanović, Biljana, Medenica, Mirjana, "Modeling of HILIC retention behavior with theoretical models and new spline interpolation technique" in Journal of Chemometrics, 31, no. 9 (2017),
https://doi.org/10.1002/cem.2910 . .

TY  - JOUR
AU  - Tumpa, Anja
AU  - Kalinić, Marko
AU  - Jovanović, Predrag
AU  - Erić, Slavica
AU  - Rakić, Tijana
AU  - Jančić-Stojanović, Biljana
AU  - Medenica, Mirjana
PY  - 2016
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2650
AB  - In this article, retention modeling of eight aminopyridines (synthesized and characterized at the Faculty of Pharmacy) in reversed-phase high performance liquid chromatography (RP-HPLC) was performed. No data related to their retention in the RP-HPLC system were found. Knowing that, it was recognized as very important to describe their retention behavior. The influences of pH of the mobile phase and the organic modifier content on the retention factors were investigated. Two theoretical models for the dependence of retention factor of organic modifier content were tested. Then, the most reliable and accurate prediction of log k was created, testing multiple linear regression model-quantitative structure-retention relationships (MLR-QSRR) and support vector regression machine-quantitative structure-retention relationships (SVM-QSRR). Initially, 400 descriptors were calculated, but four of them (POM, log D, M-SZX/RZX and m-RPCG) were included in the models. SVM-QSRR performed significantly better than the MLR model. Apart from aminopyridines, four structurally similar substances (indapamide, gliclazide, sulfamethoxazole and furosemide) were followed in the same chromatographic system. They were used as external validation set for the QSRR model (it performed well within its applicability domain, which was defined using a bounding box approach). After having described retention of eight aminopyridines with both theoretical and QSRR models, further investigations in this field can be conducted.
PB  - Oxford Univ Press Inc, Cary
T2  - Journal of Chromatographic Science
T1  - Theoretical Models and QSRR in Retention Modeling of Eight Aminopyridines
VL  - 54
IS  - 3
SP  - 436
EP  - 444
DO  - 10.1093/chromsci/bmv165
ER  - 

@article{
author = "Tumpa, Anja and Kalinić, Marko and Jovanović, Predrag and Erić, Slavica and Rakić, Tijana and Jančić-Stojanović, Biljana and Medenica, Mirjana",
year = "2016",
abstract = "In this article, retention modeling of eight aminopyridines (synthesized and characterized at the Faculty of Pharmacy) in reversed-phase high performance liquid chromatography (RP-HPLC) was performed. No data related to their retention in the RP-HPLC system were found. Knowing that, it was recognized as very important to describe their retention behavior. The influences of pH of the mobile phase and the organic modifier content on the retention factors were investigated. Two theoretical models for the dependence of retention factor of organic modifier content were tested. Then, the most reliable and accurate prediction of log k was created, testing multiple linear regression model-quantitative structure-retention relationships (MLR-QSRR) and support vector regression machine-quantitative structure-retention relationships (SVM-QSRR). Initially, 400 descriptors were calculated, but four of them (POM, log D, M-SZX/RZX and m-RPCG) were included in the models. SVM-QSRR performed significantly better than the MLR model. Apart from aminopyridines, four structurally similar substances (indapamide, gliclazide, sulfamethoxazole and furosemide) were followed in the same chromatographic system. They were used as external validation set for the QSRR model (it performed well within its applicability domain, which was defined using a bounding box approach). After having described retention of eight aminopyridines with both theoretical and QSRR models, further investigations in this field can be conducted.",
publisher = "Oxford Univ Press Inc, Cary",
journal = "Journal of Chromatographic Science",
title = "Theoretical Models and QSRR in Retention Modeling of Eight Aminopyridines",
volume = "54",
number = "3",
pages = "436-444",
doi = "10.1093/chromsci/bmv165"
}

Tumpa, A., Kalinić, M., Jovanović, P., Erić, S., Rakić, T., Jančić-Stojanović, B.,& Medenica, M.. (2016). Theoretical Models and QSRR in Retention Modeling of Eight Aminopyridines. in Journal of Chromatographic Science
Oxford Univ Press Inc, Cary., 54(3), 436-444.
https://doi.org/10.1093/chromsci/bmv165

Tumpa A, Kalinić M, Jovanović P, Erić S, Rakić T, Jančić-Stojanović B, Medenica M. Theoretical Models and QSRR in Retention Modeling of Eight Aminopyridines. in Journal of Chromatographic Science. 2016;54(3):436-444.
doi:10.1093/chromsci/bmv165 .

Tumpa, Anja, Kalinić, Marko, Jovanović, Predrag, Erić, Slavica, Rakić, Tijana, Jančić-Stojanović, Biljana, Medenica, Mirjana, "Theoretical Models and QSRR in Retention Modeling of Eight Aminopyridines" in Journal of Chromatographic Science, 54, no. 3 (2016):436-444,
https://doi.org/10.1093/chromsci/bmv165 . .

TY  - JOUR
AU  - Vemić, Ana
AU  - Kalinić, Marko
AU  - Erić, Slavica
AU  - Malenović, Anđelija
AU  - Medenica, Mirjana
PY  - 2015
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2383
AB  - The aim of this study was to examine the interaction of the chaotropic salts of different position in Hofmeister series (CF3COONa, NaClO4, NaPF6) added to the mobile phase with the stationary phases of different hydrophobicity (C8 and C18 XTerra (R) columns), as well as their common influence on the retention behavior of pramipexole and its structurally related impurities. The extended thermodynamic approach enabled the understanding of the underlying separation mechanism. Comparing six different column-salt systems it was observed that general system hydrophobicity presented by salt chaotropicity and column hydrophobicity favors stationary phase ion-pairing over the ion-pair formation in the eluent. Further, an attempt was made to describe the influence of analytes' nature on their retention behavior in such chromatographic systems. An analysis is performed in order to select and elucidate the molecular descriptors (electrostatical, quantum-chemical, geometrical, topological, and constitutional) that best explain the experimental evidence and findings obtained by the thermodynamic approach. The results of this analysis suggest that analytes' charge distribution and its complementarity to the structure of the electric double layer formed on the surface of the stationary phase upon the addition of chaotropic additives can be useful for understanding the differences in retention of structurally related analytes. These findings provide a novel understanding of the interactions between all the components of the chromatographic system containing chaotropic additive and a good basis for further investigations suggesting the development of generally applicable predictors in structure-retention relationship studies in related chromatographic systems.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Chromatography A
T1  - The influence of salt chaotropicity, column hydrophobicity and analytes' molecular properties on the retention of pramipexole and its impurities
VL  - 1386
SP  - 39
EP  - 46
DO  - 10.1016/j.chroma.2015.01.078
ER  - 

@article{
author = "Vemić, Ana and Kalinić, Marko and Erić, Slavica and Malenović, Anđelija and Medenica, Mirjana",
year = "2015",
abstract = "The aim of this study was to examine the interaction of the chaotropic salts of different position in Hofmeister series (CF3COONa, NaClO4, NaPF6) added to the mobile phase with the stationary phases of different hydrophobicity (C8 and C18 XTerra (R) columns), as well as their common influence on the retention behavior of pramipexole and its structurally related impurities. The extended thermodynamic approach enabled the understanding of the underlying separation mechanism. Comparing six different column-salt systems it was observed that general system hydrophobicity presented by salt chaotropicity and column hydrophobicity favors stationary phase ion-pairing over the ion-pair formation in the eluent. Further, an attempt was made to describe the influence of analytes' nature on their retention behavior in such chromatographic systems. An analysis is performed in order to select and elucidate the molecular descriptors (electrostatical, quantum-chemical, geometrical, topological, and constitutional) that best explain the experimental evidence and findings obtained by the thermodynamic approach. The results of this analysis suggest that analytes' charge distribution and its complementarity to the structure of the electric double layer formed on the surface of the stationary phase upon the addition of chaotropic additives can be useful for understanding the differences in retention of structurally related analytes. These findings provide a novel understanding of the interactions between all the components of the chromatographic system containing chaotropic additive and a good basis for further investigations suggesting the development of generally applicable predictors in structure-retention relationship studies in related chromatographic systems.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Chromatography A",
title = "The influence of salt chaotropicity, column hydrophobicity and analytes' molecular properties on the retention of pramipexole and its impurities",
volume = "1386",
pages = "39-46",
doi = "10.1016/j.chroma.2015.01.078"
}

Vemić, A., Kalinić, M., Erić, S., Malenović, A.,& Medenica, M.. (2015). The influence of salt chaotropicity, column hydrophobicity and analytes' molecular properties on the retention of pramipexole and its impurities. in Journal of Chromatography A
Elsevier Science BV, Amsterdam., 1386, 39-46.
https://doi.org/10.1016/j.chroma.2015.01.078

Vemić A, Kalinić M, Erić S, Malenović A, Medenica M. The influence of salt chaotropicity, column hydrophobicity and analytes' molecular properties on the retention of pramipexole and its impurities. in Journal of Chromatography A. 2015;1386:39-46.
doi:10.1016/j.chroma.2015.01.078 .

Vemić, Ana, Kalinić, Marko, Erić, Slavica, Malenović, Anđelija, Medenica, Mirjana, "The influence of salt chaotropicity, column hydrophobicity and analytes' molecular properties on the retention of pramipexole and its impurities" in Journal of Chromatography A, 1386 (2015):39-46,
https://doi.org/10.1016/j.chroma.2015.01.078 . .

TY  - JOUR
AU  - Pantović, Jasmina
AU  - Malenović, Anđelija
AU  - Vemić, Ana
AU  - Kostić, Nada
AU  - Medenica, Mirjana
PY  - 2015
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2454
AB  - In this paper, the development of reversed-phase liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality by design (QbD) approach is presented. The defined analytical target profile (ATP) was the efficient baseline separation and the accurate determination of the investigated analytes. The selected critical quality attributes (CQAs) were the separation criterions between the critical peak pairs because the mixture complexity imposed a gradient elution mode. The critical process parameters (CPPs) studied in this research were acetonitrile content at the beginning of gradient program, acetonitrile content at the end of gradient program and the gradient time. Plan of experiments was defined by Box-Behnken design. The experimental domains of the three selected factors x1 - content of the acetonitrile at the start of linear gradient, x2 - content of the acetonitrile at the end of linear gradient and x3 - gradient time (t(G)) were 110%, 30%], [48%, 60%] and [8 min, 15 min], respectively. In order to define the design space (DS) as a zone where the desired quality criteria is met providing also the quality assurance, Monte Carlo simulations were performed. The uniform error distribution equal to the calculated standard error was added to the model coefficient estimates. Monte Carlo simulation included 5000 iterations in each of 3969 defined grid points and the region having the probability pi >= 95% to achieve satisfactory values of all defined CQAs was computed. As a working point, following chromatographic conditions suited in the middle of the DS were chosen: 22% acetonitrile at the start of gradient program, 55.5% acetonitrile at the end of gradient program end and the gradient time of 11.5 min. The developed method was validated in order to prove its reliability.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Development of liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality-by-design methodology
VL  - 111
SP  - 7
EP  - 13
DO  - 10.1016/j.jpba.2015.03.009
ER  - 

@article{
author = "Pantović, Jasmina and Malenović, Anđelija and Vemić, Ana and Kostić, Nada and Medenica, Mirjana",
year = "2015",
abstract = "In this paper, the development of reversed-phase liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality by design (QbD) approach is presented. The defined analytical target profile (ATP) was the efficient baseline separation and the accurate determination of the investigated analytes. The selected critical quality attributes (CQAs) were the separation criterions between the critical peak pairs because the mixture complexity imposed a gradient elution mode. The critical process parameters (CPPs) studied in this research were acetonitrile content at the beginning of gradient program, acetonitrile content at the end of gradient program and the gradient time. Plan of experiments was defined by Box-Behnken design. The experimental domains of the three selected factors x1 - content of the acetonitrile at the start of linear gradient, x2 - content of the acetonitrile at the end of linear gradient and x3 - gradient time (t(G)) were 110%, 30%], [48%, 60%] and [8 min, 15 min], respectively. In order to define the design space (DS) as a zone where the desired quality criteria is met providing also the quality assurance, Monte Carlo simulations were performed. The uniform error distribution equal to the calculated standard error was added to the model coefficient estimates. Monte Carlo simulation included 5000 iterations in each of 3969 defined grid points and the region having the probability pi >= 95% to achieve satisfactory values of all defined CQAs was computed. As a working point, following chromatographic conditions suited in the middle of the DS were chosen: 22% acetonitrile at the start of gradient program, 55.5% acetonitrile at the end of gradient program end and the gradient time of 11.5 min. The developed method was validated in order to prove its reliability.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Development of liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality-by-design methodology",
volume = "111",
pages = "7-13",
doi = "10.1016/j.jpba.2015.03.009"
}

Pantović, J., Malenović, A., Vemić, A., Kostić, N.,& Medenica, M.. (2015). Development of liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality-by-design methodology. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 111, 7-13.
https://doi.org/10.1016/j.jpba.2015.03.009

Pantović J, Malenović A, Vemić A, Kostić N, Medenica M. Development of liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality-by-design methodology. in Journal of Pharmaceutical and Biomedical Analysis. 2015;111:7-13.
doi:10.1016/j.jpba.2015.03.009 .

Pantović, Jasmina, Malenović, Anđelija, Vemić, Ana, Kostić, Nada, Medenica, Mirjana, "Development of liquid chromatographic method for the analysis of dabigatran etexilate mesilate and its ten impurities supported by quality-by-design methodology" in Journal of Pharmaceutical and Biomedical Analysis, 111 (2015):7-13,
https://doi.org/10.1016/j.jpba.2015.03.009 . .

TY  - JOUR
AU  - Kostić, Nada
AU  - Dotsikas, Yannis
AU  - Jović, Nebojša
AU  - Stevanović, Galina
AU  - Malenović, Anđelija
AU  - Medenica, Mirjana
PY  - 2015
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2410
AB  - In this paper, novel LC-MS/MS methods for the determination of antiepileptic drug pregabalin in dried matrix spots (DMS) are presented. This attractive technique of sample collection in micro amount was utilized in the form of dried blood spots (DBS) and dried plasma spots (DPS). Following a pre-column derivatization procedure, using n-propyl chloroformate in the presence of n-propanol, and consecutive liquid-liquid extraction, derivatized pregabalin and its internal standard, 4-aminocyclohexanecarboxylic acid, were detected in positive ion mode by applying two SRM transitions per analyte. A YMC-Pack Octyl column (50 mm x 4.0 mm, 3 mu m particle size) maintained at 30 degrees C, was utilized with running mobile phase composed of acetonitrile: 0.15% formic acid (85:15, v/v). Flow rate was 550 mu L/min and total run time 2 min. Established methods were fully validated over the concentration range of 0.200-20.0 mu g/mL for DBS and 0.400-40.0 mu g/mL for DPS, respectively, while specificity, accuracy, precision, recovery, matrix-effect, stability, dilution integrity and spot homogeneity were found within acceptance criteria. Validated methods were applied for the determination of pregabalin levels in dried blood and plasma samples obtained from patients with epilepsy, after per os administration of commercial capsules. Comparison of drug level in blood and plasma, as well as correction steps undertaken in order to overcome hematocrit issue, when analyzing DBS, are also given.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Quantitation of pregabalin in dried blood spots and dried plasma spots by validated LC-MS/MS methods
VL  - 109
SP  - 79
EP  - 84
DO  - 10.1016/j.jpba.2015.02.023
ER  - 

@article{
author = "Kostić, Nada and Dotsikas, Yannis and Jović, Nebojša and Stevanović, Galina and Malenović, Anđelija and Medenica, Mirjana",
year = "2015",
abstract = "In this paper, novel LC-MS/MS methods for the determination of antiepileptic drug pregabalin in dried matrix spots (DMS) are presented. This attractive technique of sample collection in micro amount was utilized in the form of dried blood spots (DBS) and dried plasma spots (DPS). Following a pre-column derivatization procedure, using n-propyl chloroformate in the presence of n-propanol, and consecutive liquid-liquid extraction, derivatized pregabalin and its internal standard, 4-aminocyclohexanecarboxylic acid, were detected in positive ion mode by applying two SRM transitions per analyte. A YMC-Pack Octyl column (50 mm x 4.0 mm, 3 mu m particle size) maintained at 30 degrees C, was utilized with running mobile phase composed of acetonitrile: 0.15% formic acid (85:15, v/v). Flow rate was 550 mu L/min and total run time 2 min. Established methods were fully validated over the concentration range of 0.200-20.0 mu g/mL for DBS and 0.400-40.0 mu g/mL for DPS, respectively, while specificity, accuracy, precision, recovery, matrix-effect, stability, dilution integrity and spot homogeneity were found within acceptance criteria. Validated methods were applied for the determination of pregabalin levels in dried blood and plasma samples obtained from patients with epilepsy, after per os administration of commercial capsules. Comparison of drug level in blood and plasma, as well as correction steps undertaken in order to overcome hematocrit issue, when analyzing DBS, are also given.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Quantitation of pregabalin in dried blood spots and dried plasma spots by validated LC-MS/MS methods",
volume = "109",
pages = "79-84",
doi = "10.1016/j.jpba.2015.02.023"
}

Kostić, N., Dotsikas, Y., Jović, N., Stevanović, G., Malenović, A.,& Medenica, M.. (2015). Quantitation of pregabalin in dried blood spots and dried plasma spots by validated LC-MS/MS methods. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 109, 79-84.
https://doi.org/10.1016/j.jpba.2015.02.023

Kostić N, Dotsikas Y, Jović N, Stevanović G, Malenović A, Medenica M. Quantitation of pregabalin in dried blood spots and dried plasma spots by validated LC-MS/MS methods. in Journal of Pharmaceutical and Biomedical Analysis. 2015;109:79-84.
doi:10.1016/j.jpba.2015.02.023 .

Kostić, Nada, Dotsikas, Yannis, Jović, Nebojša, Stevanović, Galina, Malenović, Anđelija, Medenica, Mirjana, "Quantitation of pregabalin in dried blood spots and dried plasma spots by validated LC-MS/MS methods" in Journal of Pharmaceutical and Biomedical Analysis, 109 (2015):79-84,
https://doi.org/10.1016/j.jpba.2015.02.023 . .

TY  - JOUR
AU  - Vemić, Ana
AU  - Rakić, Tijana
AU  - Malenović, Anđelija
AU  - Medenica, Mirjana
PY  - 2015
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2379
AB  - The aim of this paper is to present a development of liquid chromatographic method when chaotropic salts are used as mobile phase additives following the QbD principles. The effect of critical process parameters (column chemistry, salt nature and concentration, acetonitrile content and column temperature) on the critical quality attributes (retention of the first and last eluting peak and separation of the critical peak pairs) was studied applying the design of experiments-design space methodology (DoE-DS). D-optimal design is chosen in order to simultaneously examine both categorical and numerical factors in minimal number of experiments. Two ways for the achievement of quality assurance were performed and compared. Namely, the uncertainty originating from the models was assessed by Monte Carlo simulations propagating the error equal to the variance of the model residuals and propagating the error originating from the model coefficients' calculation. The baseline separation of pramipexole and its five impurities is achieved fulfilling all the required criteria while the method validation proved its reliability.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Chaotropic salts in liquid chromatographic method development for the determination of pramipexole and its impurities following quality-by-design principles
VL  - 102
SP  - 314
EP  - 320
DO  - 10.1016/j.jpba.2014.09.031
ER  - 

@article{
author = "Vemić, Ana and Rakić, Tijana and Malenović, Anđelija and Medenica, Mirjana",
year = "2015",
abstract = "The aim of this paper is to present a development of liquid chromatographic method when chaotropic salts are used as mobile phase additives following the QbD principles. The effect of critical process parameters (column chemistry, salt nature and concentration, acetonitrile content and column temperature) on the critical quality attributes (retention of the first and last eluting peak and separation of the critical peak pairs) was studied applying the design of experiments-design space methodology (DoE-DS). D-optimal design is chosen in order to simultaneously examine both categorical and numerical factors in minimal number of experiments. Two ways for the achievement of quality assurance were performed and compared. Namely, the uncertainty originating from the models was assessed by Monte Carlo simulations propagating the error equal to the variance of the model residuals and propagating the error originating from the model coefficients' calculation. The baseline separation of pramipexole and its five impurities is achieved fulfilling all the required criteria while the method validation proved its reliability.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Chaotropic salts in liquid chromatographic method development for the determination of pramipexole and its impurities following quality-by-design principles",
volume = "102",
pages = "314-320",
doi = "10.1016/j.jpba.2014.09.031"
}

Vemić, A., Rakić, T., Malenović, A.,& Medenica, M.. (2015). Chaotropic salts in liquid chromatographic method development for the determination of pramipexole and its impurities following quality-by-design principles. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 102, 314-320.
https://doi.org/10.1016/j.jpba.2014.09.031

Vemić A, Rakić T, Malenović A, Medenica M. Chaotropic salts in liquid chromatographic method development for the determination of pramipexole and its impurities following quality-by-design principles. in Journal of Pharmaceutical and Biomedical Analysis. 2015;102:314-320.
doi:10.1016/j.jpba.2014.09.031 .

Vemić, Ana, Rakić, Tijana, Malenović, Anđelija, Medenica, Mirjana, "Chaotropic salts in liquid chromatographic method development for the determination of pramipexole and its impurities following quality-by-design principles" in Journal of Pharmaceutical and Biomedical Analysis, 102 (2015):314-320,
https://doi.org/10.1016/j.jpba.2014.09.031 . .

TY  - JOUR
AU  - Vemić, Ana
AU  - Malenović, Anđelija
AU  - Medenica, Mirjana
PY  - 2014
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2231
AB  - Chaotropic agents recently gained popularity as interesting and useful mobile phase additives in liquid chromatography due to their effect on analytes retention, peak symmetry and separation efficiency. They mimic the role of classical ion-pairing agents, but with less drawbacks, so their use becomes attractive in the field of pharmaceutical analysis. In this paper, the influence of sodium trifluoroacetate and sodium perchlorate on the chromatographic behavior of ropinirole and its impurities is examined. By the extended thermodynamic approach, it was shown that the separation in the given system was predominantly governed by electrostatic interactions between the protonated analytes and the charged surface of the stationary phase, but the ion-pair complex formation in the eluent also proved to be significant. Further, the employment of face-centered central composite design enabled the understanding of the effect of chaotropic agent concentration and its interactions with other factors (acetonitrile content and pH of the water phase) that influence the given chromatographic system. Finally, the same data was used for multi-objective optimization based on the grid point search method. After the method validation, the adequacy of the suggested approach in development of methods for routine pharmaceutical analysis was proven.
PB  - Elsevier Science BV, Amsterdam
T2  - Talanta
T1  - The influence of inorganic salts with chaotropic properties on the chromatographic behavior of ropinirole and its two impurities
VL  - 123
SP  - 122
EP  - 127
DO  - 10.1016/j.talanta.2014.02.006
ER  - 

@article{
author = "Vemić, Ana and Malenović, Anđelija and Medenica, Mirjana",
year = "2014",
abstract = "Chaotropic agents recently gained popularity as interesting and useful mobile phase additives in liquid chromatography due to their effect on analytes retention, peak symmetry and separation efficiency. They mimic the role of classical ion-pairing agents, but with less drawbacks, so their use becomes attractive in the field of pharmaceutical analysis. In this paper, the influence of sodium trifluoroacetate and sodium perchlorate on the chromatographic behavior of ropinirole and its impurities is examined. By the extended thermodynamic approach, it was shown that the separation in the given system was predominantly governed by electrostatic interactions between the protonated analytes and the charged surface of the stationary phase, but the ion-pair complex formation in the eluent also proved to be significant. Further, the employment of face-centered central composite design enabled the understanding of the effect of chaotropic agent concentration and its interactions with other factors (acetonitrile content and pH of the water phase) that influence the given chromatographic system. Finally, the same data was used for multi-objective optimization based on the grid point search method. After the method validation, the adequacy of the suggested approach in development of methods for routine pharmaceutical analysis was proven.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Talanta",
title = "The influence of inorganic salts with chaotropic properties on the chromatographic behavior of ropinirole and its two impurities",
volume = "123",
pages = "122-127",
doi = "10.1016/j.talanta.2014.02.006"
}

Vemić, A., Malenović, A.,& Medenica, M.. (2014). The influence of inorganic salts with chaotropic properties on the chromatographic behavior of ropinirole and its two impurities. in Talanta
Elsevier Science BV, Amsterdam., 123, 122-127.
https://doi.org/10.1016/j.talanta.2014.02.006

Vemić A, Malenović A, Medenica M. The influence of inorganic salts with chaotropic properties on the chromatographic behavior of ropinirole and its two impurities. in Talanta. 2014;123:122-127.
doi:10.1016/j.talanta.2014.02.006 .

Vemić, Ana, Malenović, Anđelija, Medenica, Mirjana, "The influence of inorganic salts with chaotropic properties on the chromatographic behavior of ropinirole and its two impurities" in Talanta, 123 (2014):122-127,
https://doi.org/10.1016/j.talanta.2014.02.006 . .

TY  - JOUR
AU  - Kostić, Nada
AU  - Dotsikas, Yannis
AU  - Jović, Nebojša
AU  - Stevanović, Galina
AU  - Malenović, Anđelija
AU  - Medenica, Mirjana
PY  - 2014
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2212
AB  - This paper presents a LC-MS/MS method for the determination of antiepileptic drug vigabatrin in dried plasma spots (DPS). Due to its zwitterionic chemical structure, a pre-column derivatization procedure was performed, aiming to yield enhanced ionization efficiency and improved chromatographic behaviour. Propyl chloroformate, in the presence of propanol, was selected as the best derivatization reagent, providing a strong signal along with reasonable run time. A relatively novel sample collection technique, DPS, was utilized, offering easy sample handling and analysis, using a sample in micro amount (similar to 5 mu L). Derivatized vigabatrin and its internal standard, 4-aminocyclohexanecarboxylic acid, were extracted by liquid-liquid extraction (LLE) and determined in positive ion mode by applying two SRM transitions per analyte. A Zorbax Eclipse XDB-C8 column (150 x 4.6 mm, 5 mu m particle size) maintained at 30 degrees C, was utilized with running mobile phase composed of acetonitrile: 0.15% formic acid (85:15, v/v). Flow rate was 550 mu L/min and total run time 4.5 min. The assay exhibited excellent linearity over the concentration range of 0.500-50.0 mu g/mL, which is suitable for the determination of vigabatrin level after per os administration in children and youths with epilepsy, who were on vigabatrin therapy, with or without co-medication. Specificity, accuracy, precision, recovery, matrix-effect and stability were also estimated and assessed within acceptance criteria.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences
T1  - Vigabatrin in dried plasma spots: Validation of a novel LC-MS/MS method and application to clinical practice
VL  - 962
SP  - 102
EP  - 108
DO  - 10.1016/j.jchromb.2014.05.037
ER  - 

@article{
author = "Kostić, Nada and Dotsikas, Yannis and Jović, Nebojša and Stevanović, Galina and Malenović, Anđelija and Medenica, Mirjana",
year = "2014",
abstract = "This paper presents a LC-MS/MS method for the determination of antiepileptic drug vigabatrin in dried plasma spots (DPS). Due to its zwitterionic chemical structure, a pre-column derivatization procedure was performed, aiming to yield enhanced ionization efficiency and improved chromatographic behaviour. Propyl chloroformate, in the presence of propanol, was selected as the best derivatization reagent, providing a strong signal along with reasonable run time. A relatively novel sample collection technique, DPS, was utilized, offering easy sample handling and analysis, using a sample in micro amount (similar to 5 mu L). Derivatized vigabatrin and its internal standard, 4-aminocyclohexanecarboxylic acid, were extracted by liquid-liquid extraction (LLE) and determined in positive ion mode by applying two SRM transitions per analyte. A Zorbax Eclipse XDB-C8 column (150 x 4.6 mm, 5 mu m particle size) maintained at 30 degrees C, was utilized with running mobile phase composed of acetonitrile: 0.15% formic acid (85:15, v/v). Flow rate was 550 mu L/min and total run time 4.5 min. The assay exhibited excellent linearity over the concentration range of 0.500-50.0 mu g/mL, which is suitable for the determination of vigabatrin level after per os administration in children and youths with epilepsy, who were on vigabatrin therapy, with or without co-medication. Specificity, accuracy, precision, recovery, matrix-effect and stability were also estimated and assessed within acceptance criteria.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences",
title = "Vigabatrin in dried plasma spots: Validation of a novel LC-MS/MS method and application to clinical practice",
volume = "962",
pages = "102-108",
doi = "10.1016/j.jchromb.2014.05.037"
}

Kostić, N., Dotsikas, Y., Jović, N., Stevanović, G., Malenović, A.,& Medenica, M.. (2014). Vigabatrin in dried plasma spots: Validation of a novel LC-MS/MS method and application to clinical practice. in Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences
Elsevier Science BV, Amsterdam., 962, 102-108.
https://doi.org/10.1016/j.jchromb.2014.05.037

Kostić N, Dotsikas Y, Jović N, Stevanović G, Malenović A, Medenica M. Vigabatrin in dried plasma spots: Validation of a novel LC-MS/MS method and application to clinical practice. in Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences. 2014;962:102-108.
doi:10.1016/j.jchromb.2014.05.037 .

Kostić, Nada, Dotsikas, Yannis, Jović, Nebojša, Stevanović, Galina, Malenović, Anđelija, Medenica, Mirjana, "Vigabatrin in dried plasma spots: Validation of a novel LC-MS/MS method and application to clinical practice" in Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences, 962 (2014):102-108,
https://doi.org/10.1016/j.jchromb.2014.05.037 . .

TY  - JOUR
AU  - Colović, Jelena
AU  - Vemić, Ana
AU  - Kostić, Nada
AU  - Malenović, Anđelija
AU  - Medenica, Mirjana
PY  - 2014
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2092
AB  - In this paper, the capability of a polynomial-modified Gaussian model to relate the peak shape of basic analytes, amlodipine, and its impurity A, with the change of chromatographic conditions was tested. For the accurate simulation of real chromatographic peaks the authors proposed the three-step procedure based on indirect modeling of peak width at 10% of peak height (W-0.1), individual values of left-half width (A) and right-half width (B), number of theoretical plates (N), and tailing factor (Tf). The values of retention factors corresponding to the peak beginning (k(B)), peak apex (k(A)), peak ending (k(E)), and peak heights (H-0) of the analytes were directly modeled. Then, the investigated experimental domain was divided to acquire a grid of appropriate density, which allowed the subsequent calculation of W-0.1, A, B, N, and Tf. On the basis of the predicted results for Tf and N, as well as the defined criteria for the simulation the following conditions were selected: 33% acetonitrile/67% aqueous phase (55 mM perchloric acid, pH 2.2) at 40 degrees C column temperature. Perfect agreement between predicted and experimental values was obtained confirming the ability of polynomial modified Gaussian model and three-step procedure to successfully simulate the real chromatograms in ion-interaction chromatography.
PB  - Wiley-VCH Verlag GMBH, Weinheim
T2  - Journal of Separation Science
T1  - Testing the capability of a polynomial-modified gaussian model in the description and simulation of chromatographic peaks of amlodipine and its impurity in ion-interaction chromatography
VL  - 37
IS  - 14
SP  - 1797
EP  - 1804
DO  - 10.1002/jssc.201400206
ER  - 

@article{
author = "Colović, Jelena and Vemić, Ana and Kostić, Nada and Malenović, Anđelija and Medenica, Mirjana",
year = "2014",
abstract = "In this paper, the capability of a polynomial-modified Gaussian model to relate the peak shape of basic analytes, amlodipine, and its impurity A, with the change of chromatographic conditions was tested. For the accurate simulation of real chromatographic peaks the authors proposed the three-step procedure based on indirect modeling of peak width at 10% of peak height (W-0.1), individual values of left-half width (A) and right-half width (B), number of theoretical plates (N), and tailing factor (Tf). The values of retention factors corresponding to the peak beginning (k(B)), peak apex (k(A)), peak ending (k(E)), and peak heights (H-0) of the analytes were directly modeled. Then, the investigated experimental domain was divided to acquire a grid of appropriate density, which allowed the subsequent calculation of W-0.1, A, B, N, and Tf. On the basis of the predicted results for Tf and N, as well as the defined criteria for the simulation the following conditions were selected: 33% acetonitrile/67% aqueous phase (55 mM perchloric acid, pH 2.2) at 40 degrees C column temperature. Perfect agreement between predicted and experimental values was obtained confirming the ability of polynomial modified Gaussian model and three-step procedure to successfully simulate the real chromatograms in ion-interaction chromatography.",
publisher = "Wiley-VCH Verlag GMBH, Weinheim",
journal = "Journal of Separation Science",
title = "Testing the capability of a polynomial-modified gaussian model in the description and simulation of chromatographic peaks of amlodipine and its impurity in ion-interaction chromatography",
volume = "37",
number = "14",
pages = "1797-1804",
doi = "10.1002/jssc.201400206"
}

Colović, J., Vemić, A., Kostić, N., Malenović, A.,& Medenica, M.. (2014). Testing the capability of a polynomial-modified gaussian model in the description and simulation of chromatographic peaks of amlodipine and its impurity in ion-interaction chromatography. in Journal of Separation Science
Wiley-VCH Verlag GMBH, Weinheim., 37(14), 1797-1804.
https://doi.org/10.1002/jssc.201400206

Colović J, Vemić A, Kostić N, Malenović A, Medenica M. Testing the capability of a polynomial-modified gaussian model in the description and simulation of chromatographic peaks of amlodipine and its impurity in ion-interaction chromatography. in Journal of Separation Science. 2014;37(14):1797-1804.
doi:10.1002/jssc.201400206 .

Colović, Jelena, Vemić, Ana, Kostić, Nada, Malenović, Anđelija, Medenica, Mirjana, "Testing the capability of a polynomial-modified gaussian model in the description and simulation of chromatographic peaks of amlodipine and its impurity in ion-interaction chromatography" in Journal of Separation Science, 37, no. 14 (2014):1797-1804,
https://doi.org/10.1002/jssc.201400206 . .

TY  - JOUR
AU  - Rakić, Tijana
AU  - Jovanović, Marko
AU  - Tumpa, Anja
AU  - Jančić-Stojanović, Biljana
AU  - Medenica, Mirjana
PY  - 2014
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2277
AB  - This paper presents the robust optimization of hydrophilic interaction liquid chromatographic method for the analysis of bisoprolol and its impurities A and C. Chemometric strategy is applied for detailed understanding of system's behavior and establishing the mathematical relationship between investigated factors (acetonitrile content in the mobile phase, pH of the water phase and buffer concentration in the water phase) and chromatographic responses. Grid point search methodology is then performed with the aim to identify the point with satisfactory separation quality for all analyzed substances and to achieve minimal analysis duration. Oversized chromatograms are made creating an extra band broadening for each chromatographic peak corresponding to the value of standard deviation in order to evaluate the incertitude originating from the model uncertainty. On the other hand, the uncertainty originating from the variation of experimental parameters is assessed by simulated experimental design robustness testing. Finally, the obtained robust optimal conditions were: chromatographic column Kinetex HILIC 100Å (100 mm x 4.5 mm, 2.6 mm particle size); mobile phase composed of acetonitrile - water phase (35 mM ammonium acetate, pH 4.9 adjusted with glacial acetic acid) (85:15 v/v); flow rate 1 mL min-1, column temperature 30°C and UV detection at 254 nm.
AB  - U ovom radu prikazana je optimizacija metode tečne hromatografije hidrofilnih interakcija za analizu bisoprolola i njegovih nečistoća A i C uz procenu mogućnosti variranja položaja pikova. Primenjena je hemometrijska strategija za detaljno razumevanje ponašanja sistema i uspostavljanje matematičke veze između ispitivanih faktora (sadržaj acetonitrila u mobilnoj fazi, pH vrednost vodene faze i koncentracija pufera u vodenoj fazi) i hromatografskih odgovora. Enumerativna tehnika optimizacije upotrebljena je za identifikaciju tačke koja pokazuje zadovoljavajući kvalitet razdvajanja svih ispitivanih supstanci i minimalno vreme trajanja analize. Kreirani su prošireni hromatogrami širenjem pikova svih ispitivanih supstanci za vrednosti standardne devijacije kako bi se procenila mogućnost greške odgovora koja potiče iz greške matematičkog modela. Mogućnost greške koja potiče iz greške u podešavanju eksperimentalnih parametara procenjena je simuliranim testiranjem robusnosti primenom eksperimentalnog dizajna. Konačno, dobijeni optimalni uslovi bili su: hromatografska kolona Kinetex HILIC 100Å (100 mm x 4,5 mm, 2,6 mm veličina čestica); mobilna faza sastavljena od smeše acetonitril - vodena faza (35 mM amonijum-acetat, pH 4,9 podešen glacijalnom sirćetnom kiselinom) (85:15 v/v); protok 1 mL min-1, temperatura kolone 30°C i UV detekcija na 254 nm.
PB  - Savez farmaceutskih udruženja Srbije, Beograd
T2  - Arhiv za farmaciju
T1  - Optimization of HILIC method for the analysis of bisoprolol and its impurities considering uncertainties in peak position
T1  - Optimizacija HILIC metode za analizu bisoprolola i njegovih nečistoća uz procenu mogućnosti variranja položaja pikova
VL  - 64
IS  - 2
SP  - 95
EP  - 111
DO  - 10.5937/arhfarm1402095R
ER  - 

@article{
author = "Rakić, Tijana and Jovanović, Marko and Tumpa, Anja and Jančić-Stojanović, Biljana and Medenica, Mirjana",
year = "2014",
abstract = "This paper presents the robust optimization of hydrophilic interaction liquid chromatographic method for the analysis of bisoprolol and its impurities A and C. Chemometric strategy is applied for detailed understanding of system's behavior and establishing the mathematical relationship between investigated factors (acetonitrile content in the mobile phase, pH of the water phase and buffer concentration in the water phase) and chromatographic responses. Grid point search methodology is then performed with the aim to identify the point with satisfactory separation quality for all analyzed substances and to achieve minimal analysis duration. Oversized chromatograms are made creating an extra band broadening for each chromatographic peak corresponding to the value of standard deviation in order to evaluate the incertitude originating from the model uncertainty. On the other hand, the uncertainty originating from the variation of experimental parameters is assessed by simulated experimental design robustness testing. Finally, the obtained robust optimal conditions were: chromatographic column Kinetex HILIC 100Å (100 mm x 4.5 mm, 2.6 mm particle size); mobile phase composed of acetonitrile - water phase (35 mM ammonium acetate, pH 4.9 adjusted with glacial acetic acid) (85:15 v/v); flow rate 1 mL min-1, column temperature 30°C and UV detection at 254 nm., U ovom radu prikazana je optimizacija metode tečne hromatografije hidrofilnih interakcija za analizu bisoprolola i njegovih nečistoća A i C uz procenu mogućnosti variranja položaja pikova. Primenjena je hemometrijska strategija za detaljno razumevanje ponašanja sistema i uspostavljanje matematičke veze između ispitivanih faktora (sadržaj acetonitrila u mobilnoj fazi, pH vrednost vodene faze i koncentracija pufera u vodenoj fazi) i hromatografskih odgovora. Enumerativna tehnika optimizacije upotrebljena je za identifikaciju tačke koja pokazuje zadovoljavajući kvalitet razdvajanja svih ispitivanih supstanci i minimalno vreme trajanja analize. Kreirani su prošireni hromatogrami širenjem pikova svih ispitivanih supstanci za vrednosti standardne devijacije kako bi se procenila mogućnost greške odgovora koja potiče iz greške matematičkog modela. Mogućnost greške koja potiče iz greške u podešavanju eksperimentalnih parametara procenjena je simuliranim testiranjem robusnosti primenom eksperimentalnog dizajna. Konačno, dobijeni optimalni uslovi bili su: hromatografska kolona Kinetex HILIC 100Å (100 mm x 4,5 mm, 2,6 mm veličina čestica); mobilna faza sastavljena od smeše acetonitril - vodena faza (35 mM amonijum-acetat, pH 4,9 podešen glacijalnom sirćetnom kiselinom) (85:15 v/v); protok 1 mL min-1, temperatura kolone 30°C i UV detekcija na 254 nm.",
publisher = "Savez farmaceutskih udruženja Srbije, Beograd",
journal = "Arhiv za farmaciju",
title = "Optimization of HILIC method for the analysis of bisoprolol and its impurities considering uncertainties in peak position, Optimizacija HILIC metode za analizu bisoprolola i njegovih nečistoća uz procenu mogućnosti variranja položaja pikova",
volume = "64",
number = "2",
pages = "95-111",
doi = "10.5937/arhfarm1402095R"
}

Rakić, T., Jovanović, M., Tumpa, A., Jančić-Stojanović, B.,& Medenica, M.. (2014). Optimization of HILIC method for the analysis of bisoprolol and its impurities considering uncertainties in peak position. in Arhiv za farmaciju
Savez farmaceutskih udruženja Srbije, Beograd., 64(2), 95-111.
https://doi.org/10.5937/arhfarm1402095R

Rakić T, Jovanović M, Tumpa A, Jančić-Stojanović B, Medenica M. Optimization of HILIC method for the analysis of bisoprolol and its impurities considering uncertainties in peak position. in Arhiv za farmaciju. 2014;64(2):95-111.
doi:10.5937/arhfarm1402095R .

Rakić, Tijana, Jovanović, Marko, Tumpa, Anja, Jančić-Stojanović, Biljana, Medenica, Mirjana, "Optimization of HILIC method for the analysis of bisoprolol and its impurities considering uncertainties in peak position" in Arhiv za farmaciju, 64, no. 2 (2014):95-111,
https://doi.org/10.5937/arhfarm1402095R . .

TY  - JOUR
AU  - Jovanović, Marko
AU  - Rakić, Tijana
AU  - Jančić-Stojanović, Biljana
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2014
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2191
AB  - Hydrophilic interaction liquid chromatography (HILIC) has emerged in recent years as a valuable alternative to reversed-phase liquid chromatography in the analysis of polar compounds. Research in HILIC is divided into two directions: the assessment of the retention mechanism and retention behavior, and the development of HILIC methods. In this work, four polar neutral analytes (iohexol and its related compounds A, B, and C) were analyzed on two silica and two diol columns in HILIC mode with the aim to investigate thoroughly the retention mechanisms and retention behavior of polar neutral compounds on these four columns. The adsorption and partition contribution to the overall HILIC retention mechanism was investigated by fitting the retention data to linear (adsorption and partition) and nonlinear (mixed-retention and quadratic) theoretical models. On the other hand, the establishment of empirical second-order polynomial retention models on the basis of D-optimal design made possible the estimation of the simultaneous influence of several mobile-phase-related factors. Furthermore, these models were also used as the basis for the application of indirect modeling of the selectivity factor and a grid point search approach in order to achieve the optimal separation of analytes. After the optimization goals had been set, the grids were searched and the optimal conditions were identified. Finally, the optimized method was subjected to validation.
PB  - Springer Heidelberg, Heidelberg
T2  - Analytical and Bioanalytical Chemistry
T1  - Retention mechanism assessment and method development for the analysis of iohexol and its related compounds in hydrophilic interaction liquid chromatography
VL  - 406
IS  - 17
SP  - 4217
EP  - 4232
DO  - 10.1007/s00216-014-7808-6
ER  - 

@article{
author = "Jovanović, Marko and Rakić, Tijana and Jančić-Stojanović, Biljana and Ivanović, Darko and Medenica, Mirjana",
year = "2014",
abstract = "Hydrophilic interaction liquid chromatography (HILIC) has emerged in recent years as a valuable alternative to reversed-phase liquid chromatography in the analysis of polar compounds. Research in HILIC is divided into two directions: the assessment of the retention mechanism and retention behavior, and the development of HILIC methods. In this work, four polar neutral analytes (iohexol and its related compounds A, B, and C) were analyzed on two silica and two diol columns in HILIC mode with the aim to investigate thoroughly the retention mechanisms and retention behavior of polar neutral compounds on these four columns. The adsorption and partition contribution to the overall HILIC retention mechanism was investigated by fitting the retention data to linear (adsorption and partition) and nonlinear (mixed-retention and quadratic) theoretical models. On the other hand, the establishment of empirical second-order polynomial retention models on the basis of D-optimal design made possible the estimation of the simultaneous influence of several mobile-phase-related factors. Furthermore, these models were also used as the basis for the application of indirect modeling of the selectivity factor and a grid point search approach in order to achieve the optimal separation of analytes. After the optimization goals had been set, the grids were searched and the optimal conditions were identified. Finally, the optimized method was subjected to validation.",
publisher = "Springer Heidelberg, Heidelberg",
journal = "Analytical and Bioanalytical Chemistry",
title = "Retention mechanism assessment and method development for the analysis of iohexol and its related compounds in hydrophilic interaction liquid chromatography",
volume = "406",
number = "17",
pages = "4217-4232",
doi = "10.1007/s00216-014-7808-6"
}

Jovanović, M., Rakić, T., Jančić-Stojanović, B., Ivanović, D.,& Medenica, M.. (2014). Retention mechanism assessment and method development for the analysis of iohexol and its related compounds in hydrophilic interaction liquid chromatography. in Analytical and Bioanalytical Chemistry
Springer Heidelberg, Heidelberg., 406(17), 4217-4232.
https://doi.org/10.1007/s00216-014-7808-6

Jovanović M, Rakić T, Jančić-Stojanović B, Ivanović D, Medenica M. Retention mechanism assessment and method development for the analysis of iohexol and its related compounds in hydrophilic interaction liquid chromatography. in Analytical and Bioanalytical Chemistry. 2014;406(17):4217-4232.
doi:10.1007/s00216-014-7808-6 .

Jovanović, Marko, Rakić, Tijana, Jančić-Stojanović, Biljana, Ivanović, Darko, Medenica, Mirjana, "Retention mechanism assessment and method development for the analysis of iohexol and its related compounds in hydrophilic interaction liquid chromatography" in Analytical and Bioanalytical Chemistry, 406, no. 17 (2014):4217-4232,
https://doi.org/10.1007/s00216-014-7808-6 . .

TY  - JOUR
AU  - Rakić, Tijana
AU  - Jančić-Stojanović, Biljana
AU  - Jovanović, Marko
AU  - Malenović, Anđelija
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2013
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3419
AB  - This paper investigates the ability of seven chromatographic response functions to measure the quality of chromatograms obtained in hydrophilic interaction liquid chromatography (HILIC). First, the functions were tested on a set of simulated chromatograms and differences in their mathematical design were discussed. Second, the functions were evaluated on the experimentally obtained chromatograms in HILIC analysis of model mixture consisted of beta agonists and antagonists. The ranking of chromatograms obtained by different functions was significantly different, implying that the accuracy of the optimization procedure is strongly dependent on the function that was selected as an output. Investigation of potential drawbacks of each function was conducted and general recommendations concerning the use of chromatographic response functions in optimization strategies are proposed.
PB  - Taylor & Francis Inc, Philadelphia
T2  - Analytical Letters
T1  - Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System
VL  - 46
IS  - 8
SP  - 1198
EP  - 1212
DO  - 10.1080/00032719.2012.755689
ER  - 

@article{
author = "Rakić, Tijana and Jančić-Stojanović, Biljana and Jovanović, Marko and Malenović, Anđelija and Ivanović, Darko and Medenica, Mirjana",
year = "2013",
abstract = "This paper investigates the ability of seven chromatographic response functions to measure the quality of chromatograms obtained in hydrophilic interaction liquid chromatography (HILIC). First, the functions were tested on a set of simulated chromatograms and differences in their mathematical design were discussed. Second, the functions were evaluated on the experimentally obtained chromatograms in HILIC analysis of model mixture consisted of beta agonists and antagonists. The ranking of chromatograms obtained by different functions was significantly different, implying that the accuracy of the optimization procedure is strongly dependent on the function that was selected as an output. Investigation of potential drawbacks of each function was conducted and general recommendations concerning the use of chromatographic response functions in optimization strategies are proposed.",
publisher = "Taylor & Francis Inc, Philadelphia",
journal = "Analytical Letters",
title = "Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System",
volume = "46",
number = "8",
pages = "1198-1212",
doi = "10.1080/00032719.2012.755689"
}

Rakić, T., Jančić-Stojanović, B., Jovanović, M., Malenović, A., Ivanović, D.,& Medenica, M.. (2013). Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System. in Analytical Letters
Taylor & Francis Inc, Philadelphia., 46(8), 1198-1212.
https://doi.org/10.1080/00032719.2012.755689

Rakić T, Jančić-Stojanović B, Jovanović M, Malenović A, Ivanović D, Medenica M. Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System. in Analytical Letters. 2013;46(8):1198-1212.
doi:10.1080/00032719.2012.755689 .

Rakić, Tijana, Jančić-Stojanović, Biljana, Jovanović, Marko, Malenović, Anđelija, Ivanović, Darko, Medenica, Mirjana, "Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System" in Analytical Letters, 46, no. 8 (2013):1198-1212,
https://doi.org/10.1080/00032719.2012.755689 . .

TY  - JOUR
AU  - Jovanović, Marko
AU  - Jančić-Stojanović, Biljana
AU  - Rakić, Tijana
AU  - Malenović, Anđelija
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2013
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2001
AB  - Five different columns (two silica, two cyanopropyl and one diol) were investigated in hydrophilic interaction liquid chromatography (HILIC). For the assessment of columns behavior in HILIC mode, six basic drugs (lamotrigine, thioridazine, clozapine, chlorpheniramine, pheniramine and sulpiride) were chosen. The assessment of the influence of the concentration of organic modifier on analytes' retention on each column was provided by fitting the retention data into theoretical models. Utilizing the statistical analysis, the selection of the model that provides better prediction of the retention behavior was enabled. Dual RP-HILIC mechanism was suggested on cyanopropyl and diol columns, therefore the transition points between the two mechanisms on these columns were calculated. Furthermore, in order to investigate the impact of three factors simultaneously on the retention behavior of the analyzed substances on Betasil Silica column, chemometrically-aided empirical models were built. The experiments were conducted according to the matrix of Box-Behnken design and on the basis of the retention data, six quadratic models were obtained and their adequacy was confirmed using ANOVA test. The obtained coefficients of quadratic models enabled the elucidation of both single factor and factor interactions influence. This was also graphically presented in 3D response surface plots.
PB  - Versita, Warsaw
T2  - Central European Journal of Chemistry
T1  - Five different columns in the analysis of basic drugs in hydrophilic interaction liquid chromatography
VL  - 11
IS  - 7
SP  - 1150
EP  - 1162
DO  - 10.2478/s11532-013-0245-0
ER  - 

@article{
author = "Jovanović, Marko and Jančić-Stojanović, Biljana and Rakić, Tijana and Malenović, Anđelija and Ivanović, Darko and Medenica, Mirjana",
year = "2013",
abstract = "Five different columns (two silica, two cyanopropyl and one diol) were investigated in hydrophilic interaction liquid chromatography (HILIC). For the assessment of columns behavior in HILIC mode, six basic drugs (lamotrigine, thioridazine, clozapine, chlorpheniramine, pheniramine and sulpiride) were chosen. The assessment of the influence of the concentration of organic modifier on analytes' retention on each column was provided by fitting the retention data into theoretical models. Utilizing the statistical analysis, the selection of the model that provides better prediction of the retention behavior was enabled. Dual RP-HILIC mechanism was suggested on cyanopropyl and diol columns, therefore the transition points between the two mechanisms on these columns were calculated. Furthermore, in order to investigate the impact of three factors simultaneously on the retention behavior of the analyzed substances on Betasil Silica column, chemometrically-aided empirical models were built. The experiments were conducted according to the matrix of Box-Behnken design and on the basis of the retention data, six quadratic models were obtained and their adequacy was confirmed using ANOVA test. The obtained coefficients of quadratic models enabled the elucidation of both single factor and factor interactions influence. This was also graphically presented in 3D response surface plots.",
publisher = "Versita, Warsaw",
journal = "Central European Journal of Chemistry",
title = "Five different columns in the analysis of basic drugs in hydrophilic interaction liquid chromatography",
volume = "11",
number = "7",
pages = "1150-1162",
doi = "10.2478/s11532-013-0245-0"
}

Jovanović, M., Jančić-Stojanović, B., Rakić, T., Malenović, A., Ivanović, D.,& Medenica, M.. (2013). Five different columns in the analysis of basic drugs in hydrophilic interaction liquid chromatography. in Central European Journal of Chemistry
Versita, Warsaw., 11(7), 1150-1162.
https://doi.org/10.2478/s11532-013-0245-0

Jovanović M, Jančić-Stojanović B, Rakić T, Malenović A, Ivanović D, Medenica M. Five different columns in the analysis of basic drugs in hydrophilic interaction liquid chromatography. in Central European Journal of Chemistry. 2013;11(7):1150-1162.
doi:10.2478/s11532-013-0245-0 .

Jovanović, Marko, Jančić-Stojanović, Biljana, Rakić, Tijana, Malenović, Anđelija, Ivanović, Darko, Medenica, Mirjana, "Five different columns in the analysis of basic drugs in hydrophilic interaction liquid chromatography" in Central European Journal of Chemistry, 11, no. 7 (2013):1150-1162,
https://doi.org/10.2478/s11532-013-0245-0 . .

TY  - JOUR
AU  - Rakić, Tijana
AU  - Jančić-Stojanović, Biljana
AU  - Jovanović, Marko
AU  - Malenović, Anđelija
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2013
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2003
AB  - This paper investigates the ability of seven chromatographic response functions to measure the quality of chromatograms obtained in hydrophilic interaction liquid chromatography (HILIC). First, the functions were tested on a set of simulated chromatograms and differences in their mathematical design were discussed. Second, the functions were evaluated on the experimentally obtained chromatograms in HILIC analysis of model mixture consisted of beta agonists and antagonists. The ranking of chromatograms obtained by different functions was significantly different, implying that the accuracy of the optimization procedure is strongly dependent on the function that was selected as an output. Investigation of potential drawbacks of each function was conducted and general recommendations concerning the use of chromatographic response functions in optimization strategies are proposed.
PB  - Taylor & Francis Inc, Philadelphia
T2  - Analytical Letters
T1  - Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System
VL  - 46
IS  - 8
SP  - 1198
EP  - 1212
DO  - 10.1080/00032719.2012.755689
ER  - 

@article{
author = "Rakić, Tijana and Jančić-Stojanović, Biljana and Jovanović, Marko and Malenović, Anđelija and Ivanović, Darko and Medenica, Mirjana",
year = "2013",
abstract = "This paper investigates the ability of seven chromatographic response functions to measure the quality of chromatograms obtained in hydrophilic interaction liquid chromatography (HILIC). First, the functions were tested on a set of simulated chromatograms and differences in their mathematical design were discussed. Second, the functions were evaluated on the experimentally obtained chromatograms in HILIC analysis of model mixture consisted of beta agonists and antagonists. The ranking of chromatograms obtained by different functions was significantly different, implying that the accuracy of the optimization procedure is strongly dependent on the function that was selected as an output. Investigation of potential drawbacks of each function was conducted and general recommendations concerning the use of chromatographic response functions in optimization strategies are proposed.",
publisher = "Taylor & Francis Inc, Philadelphia",
journal = "Analytical Letters",
title = "Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System",
volume = "46",
number = "8",
pages = "1198-1212",
doi = "10.1080/00032719.2012.755689"
}

Rakić, T., Jančić-Stojanović, B., Jovanović, M., Malenović, A., Ivanović, D.,& Medenica, M.. (2013). Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System. in Analytical Letters
Taylor & Francis Inc, Philadelphia., 46(8), 1198-1212.
https://doi.org/10.1080/00032719.2012.755689

Rakić T, Jančić-Stojanović B, Jovanović M, Malenović A, Ivanović D, Medenica M. Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System. in Analytical Letters. 2013;46(8):1198-1212.
doi:10.1080/00032719.2012.755689 .

Rakić, Tijana, Jančić-Stojanović, Biljana, Jovanović, Marko, Malenović, Anđelija, Ivanović, Darko, Medenica, Mirjana, "Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System" in Analytical Letters, 46, no. 8 (2013):1198-1212,
https://doi.org/10.1080/00032719.2012.755689 . .

TY  - JOUR
AU  - Kostić, Nada
AU  - Dotsikas, Yannis
AU  - Malenović, Anđelija
AU  - Jančić-Stojanović, Biljana
AU  - Rakić, Tijana
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2013
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1967
AB  - In this article, a step-by-step optimization procedure for improving analyte response with implementation of experimental design is described. Zwitterionic antiepileptics, namely vigabatrin, pregabalin and gabapentin, were chosen as model compounds to undergo chloroformate-mediated derivatization followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. Application of a planned stepwise optimization procedure allowed responses of analytes, expressed as areas and signal-to-noise ratios, to be improved, enabling achievement of lower limit of detection values. Results from the current study demonstrate that optimization of parameters such as scan time, geometry of ion source, sheath and auxiliary gas pressure, capillary temperature, collision pressure and mobile phase composition can have a positive impact on sensitivity of LC-MS/MS methods. Optimization of LC and MS parameters led to a total increment of 53.9%, 83.3% and 95.7% in areas of derivatized vigabatrin, pregabalin and gabapentin, respectively, while for signal-to-noise values, an improvement of 140.0%, 93.6% and 124.0% was achieved, compared to autotune settings. After defining the final optimal conditions, a time-segmented method was validated for the determination of mentioned drugs in plasma. The method proved to be accurate and precise with excellent linearity for the tested concentration range (40.0ngml(-1)-10.0x10(3)ngml(-1)). Copyright
PB  - Wiley-Blackwell, Hoboken
T2  - Journal of Mass Spectrometry
T1  - Stepwise optimization approach for improving LC-MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design
VL  - 48
IS  - 7
SP  - 875
EP  - 884
DO  - 10.1002/jms.3236
ER  - 

@article{
author = "Kostić, Nada and Dotsikas, Yannis and Malenović, Anđelija and Jančić-Stojanović, Biljana and Rakić, Tijana and Ivanović, Darko and Medenica, Mirjana",
year = "2013",
abstract = "In this article, a step-by-step optimization procedure for improving analyte response with implementation of experimental design is described. Zwitterionic antiepileptics, namely vigabatrin, pregabalin and gabapentin, were chosen as model compounds to undergo chloroformate-mediated derivatization followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. Application of a planned stepwise optimization procedure allowed responses of analytes, expressed as areas and signal-to-noise ratios, to be improved, enabling achievement of lower limit of detection values. Results from the current study demonstrate that optimization of parameters such as scan time, geometry of ion source, sheath and auxiliary gas pressure, capillary temperature, collision pressure and mobile phase composition can have a positive impact on sensitivity of LC-MS/MS methods. Optimization of LC and MS parameters led to a total increment of 53.9%, 83.3% and 95.7% in areas of derivatized vigabatrin, pregabalin and gabapentin, respectively, while for signal-to-noise values, an improvement of 140.0%, 93.6% and 124.0% was achieved, compared to autotune settings. After defining the final optimal conditions, a time-segmented method was validated for the determination of mentioned drugs in plasma. The method proved to be accurate and precise with excellent linearity for the tested concentration range (40.0ngml(-1)-10.0x10(3)ngml(-1)). Copyright",
publisher = "Wiley-Blackwell, Hoboken",
journal = "Journal of Mass Spectrometry",
title = "Stepwise optimization approach for improving LC-MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design",
volume = "48",
number = "7",
pages = "875-884",
doi = "10.1002/jms.3236"
}

Kostić, N., Dotsikas, Y., Malenović, A., Jančić-Stojanović, B., Rakić, T., Ivanović, D.,& Medenica, M.. (2013). Stepwise optimization approach for improving LC-MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design. in Journal of Mass Spectrometry
Wiley-Blackwell, Hoboken., 48(7), 875-884.
https://doi.org/10.1002/jms.3236

Kostić N, Dotsikas Y, Malenović A, Jančić-Stojanović B, Rakić T, Ivanović D, Medenica M. Stepwise optimization approach for improving LC-MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design. in Journal of Mass Spectrometry. 2013;48(7):875-884.
doi:10.1002/jms.3236 .

Kostić, Nada, Dotsikas, Yannis, Malenović, Anđelija, Jančić-Stojanović, Biljana, Rakić, Tijana, Ivanović, Darko, Medenica, Mirjana, "Stepwise optimization approach for improving LC-MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design" in Journal of Mass Spectrometry, 48, no. 7 (2013):875-884,
https://doi.org/10.1002/jms.3236 . .

TY  - JOUR
AU  - Rakić, Tijana
AU  - Vemić, Sava
AU  - Jančić-Stojanović, Biljana
AU  - Medenica, Mirjana
PY  - 2013
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1947
AB  - This paper proposes an innovative concept for robustness evaluation guided by two crucial aims: indubitable identification of the factors that significantly affect the LC method and avoidance of unnecessary time and money wasting. The first phase of the proposed strategy includes robustness screening during the method optimization. Initial assumptions of the method robustness can be tracked as the rate of the response change while the factors deviate within the expected range. Therefore, partial and total robustness criteria are calculated. If the results obtained are not satisfactory, re-optimization of the method should be considered. Otherwise, extensive robustness testing defined by experimental design and multi-level factors estimation should be performed to confirm the method robustness. Firstly, the important factors are investigated by the standard graphical (normal probability plots) and statistical (algorithm of Dong and error estimation based on a priori declared negligible effects) procedures. Since these approaches have several drawbacks, they can result in the appearance of false negative or false positive results. Thus, the modification of the statistical tests is advised in order to make the final conclusions. Special attention was dedicated to the advantages of the adapted algorithm of Dong (so-called 75 % approach) in the absence of the effect sparsity. The new approach is presented on the optimization and robustness testing of LC method for determination of ramipril and its five impurities. It is proved that the proposed strategy can perform an overall robustness estimation and successfully reveal all important factors.
PB  - Springer Heidelberg, Heidelberg
T2  - Chromatographia
T1  - Multi-Level Robustness Evaluation Approach: From Robustness Criterion to Adapted Algorithm of Dong
VL  - 76
IS  - 5-6
SP  - 267
EP  - 277
DO  - 10.1007/s10337-012-2317-2
ER  - 

@article{
author = "Rakić, Tijana and Vemić, Sava and Jančić-Stojanović, Biljana and Medenica, Mirjana",
year = "2013",
abstract = "This paper proposes an innovative concept for robustness evaluation guided by two crucial aims: indubitable identification of the factors that significantly affect the LC method and avoidance of unnecessary time and money wasting. The first phase of the proposed strategy includes robustness screening during the method optimization. Initial assumptions of the method robustness can be tracked as the rate of the response change while the factors deviate within the expected range. Therefore, partial and total robustness criteria are calculated. If the results obtained are not satisfactory, re-optimization of the method should be considered. Otherwise, extensive robustness testing defined by experimental design and multi-level factors estimation should be performed to confirm the method robustness. Firstly, the important factors are investigated by the standard graphical (normal probability plots) and statistical (algorithm of Dong and error estimation based on a priori declared negligible effects) procedures. Since these approaches have several drawbacks, they can result in the appearance of false negative or false positive results. Thus, the modification of the statistical tests is advised in order to make the final conclusions. Special attention was dedicated to the advantages of the adapted algorithm of Dong (so-called 75 % approach) in the absence of the effect sparsity. The new approach is presented on the optimization and robustness testing of LC method for determination of ramipril and its five impurities. It is proved that the proposed strategy can perform an overall robustness estimation and successfully reveal all important factors.",
publisher = "Springer Heidelberg, Heidelberg",
journal = "Chromatographia",
title = "Multi-Level Robustness Evaluation Approach: From Robustness Criterion to Adapted Algorithm of Dong",
volume = "76",
number = "5-6",
pages = "267-277",
doi = "10.1007/s10337-012-2317-2"
}

Rakić, T., Vemić, S., Jančić-Stojanović, B.,& Medenica, M.. (2013). Multi-Level Robustness Evaluation Approach: From Robustness Criterion to Adapted Algorithm of Dong. in Chromatographia
Springer Heidelberg, Heidelberg., 76(5-6), 267-277.
https://doi.org/10.1007/s10337-012-2317-2

Rakić T, Vemić S, Jančić-Stojanović B, Medenica M. Multi-Level Robustness Evaluation Approach: From Robustness Criterion to Adapted Algorithm of Dong. in Chromatographia. 2013;76(5-6):267-277.
doi:10.1007/s10337-012-2317-2 .

Rakić, Tijana, Vemić, Sava, Jančić-Stojanović, Biljana, Medenica, Mirjana, "Multi-Level Robustness Evaluation Approach: From Robustness Criterion to Adapted Algorithm of Dong" in Chromatographia, 76, no. 5-6 (2013):267-277,
https://doi.org/10.1007/s10337-012-2317-2 . .

TY  - JOUR
AU  - Kostić, Nada
AU  - Dotsikas, Yannis
AU  - Malenović, Anđelija
AU  - Medenica, Mirjana
PY  - 2013
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1911
AB  - In the current study, three antiepileptic drugs with zwitterionic properties, namely vigabatrin, pregabalin and gabapentin, were chosen as model analytes to undergo derivatization by applying various n-alkyl chloroformate/n-alcohol combinations, followed by LC-ESI-MS/MS analysis. The employment of 16 combinations per drug using methyl, ethyl, propyl or butyl chloroformate coupled with methanol, ethanol, propanol or butanol, greatly affected a series of parameters of the derivatives, such as retention time on C8 column, signal expressed via areas, limit of detection values, as well as the yields of the main and side reactions. Practically, even slight modification of n-alkyl group of either chloroformate or alcohol resulted in significant changes in the chromatographic and mass spectrometric behavior of the novel derivative. It was clearly demonstrated that all the estimated parameters were highly correlated with the length of n-alkyl groups of the involved chloroformate and alcohol. The most significant influence was monitored in peak area values, indicating that the length of the n-alkyl chain plays an important role in electrospray ionization efficiency. For this parameter, increasing the n-alkyl chain from methyl to butyl led to increment up to 2089%, 508.7% and 1075% for area values of derivatized vigabatrin, pregabalin and gabapentin, respectively. These changes affected also the corresponding values of limits of detection, with the estimated improvements up to 1553%, 397.7% and 875.0% for the aforementioned derivatized drugs, respectively. Besides the obvious utilization of these conclusions in the development of bioanalytical methods for these analytes with the current protocol, this study offers valuable data which can be useful in more general approaches, giving insights into the effects of this derivatization reaction and its performances.
PB  - Elsevier Science BV, Amsterdam
T2  - Talanta
T1  - Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs
VL  - 116
SP  - 91
EP  - 99
DO  - 10.1016/j.talanta.2013.04.082
ER  - 

@article{
author = "Kostić, Nada and Dotsikas, Yannis and Malenović, Anđelija and Medenica, Mirjana",
year = "2013",
abstract = "In the current study, three antiepileptic drugs with zwitterionic properties, namely vigabatrin, pregabalin and gabapentin, were chosen as model analytes to undergo derivatization by applying various n-alkyl chloroformate/n-alcohol combinations, followed by LC-ESI-MS/MS analysis. The employment of 16 combinations per drug using methyl, ethyl, propyl or butyl chloroformate coupled with methanol, ethanol, propanol or butanol, greatly affected a series of parameters of the derivatives, such as retention time on C8 column, signal expressed via areas, limit of detection values, as well as the yields of the main and side reactions. Practically, even slight modification of n-alkyl group of either chloroformate or alcohol resulted in significant changes in the chromatographic and mass spectrometric behavior of the novel derivative. It was clearly demonstrated that all the estimated parameters were highly correlated with the length of n-alkyl groups of the involved chloroformate and alcohol. The most significant influence was monitored in peak area values, indicating that the length of the n-alkyl chain plays an important role in electrospray ionization efficiency. For this parameter, increasing the n-alkyl chain from methyl to butyl led to increment up to 2089%, 508.7% and 1075% for area values of derivatized vigabatrin, pregabalin and gabapentin, respectively. These changes affected also the corresponding values of limits of detection, with the estimated improvements up to 1553%, 397.7% and 875.0% for the aforementioned derivatized drugs, respectively. Besides the obvious utilization of these conclusions in the development of bioanalytical methods for these analytes with the current protocol, this study offers valuable data which can be useful in more general approaches, giving insights into the effects of this derivatization reaction and its performances.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Talanta",
title = "Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs",
volume = "116",
pages = "91-99",
doi = "10.1016/j.talanta.2013.04.082"
}

Kostić, N., Dotsikas, Y., Malenović, A.,& Medenica, M.. (2013). Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs. in Talanta
Elsevier Science BV, Amsterdam., 116, 91-99.
https://doi.org/10.1016/j.talanta.2013.04.082

Kostić N, Dotsikas Y, Malenović A, Medenica M. Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs. in Talanta. 2013;116:91-99.
doi:10.1016/j.talanta.2013.04.082 .

Kostić, Nada, Dotsikas, Yannis, Malenović, Anđelija, Medenica, Mirjana, "Effects of derivatization reagents consisting of n-alkyl chloroformate/n-alcohol combinations in LC-ESI-MS/MS analysis of zwitterionic antiepileptic drugs" in Talanta, 116 (2013):91-99,
https://doi.org/10.1016/j.talanta.2013.04.082 . .

TY  - JOUR
AU  - Rakić, Tijana
AU  - Stanimirović, Zorica
AU  - Denić, Aleksandar
AU  - Marić, Miroslav
AU  - Jančić-Stojanović, Biljana
AU  - Medenica, Mirjana
PY  - 2013
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1895
AB  - A novel approach to mathematical modeling of chromatographic responses based on interpolation polynomials with divided differences and with finite differences is discussed. These interpolational techniques as well as traditionally applied second-order polynomial models obtained by least squares are compared. Interpolation techniques can be useful in situations where commonly used linear or quadratic models are not applicable: when the nature of dependence is complex or the investigated factor intervals are broad. The three analyzed modeling techniques are incorporated in a design of experiments methodology for systematic development and optimization of liquid chromatographic methods. The direct modeling of retention factors is carried out first, while the objective function for final quality measurement is calculated last. An interpolation polynomial with divided differences resulted in a high quality fit compared with the results obtained by the other two modeling approaches and succeeded in locating the desired optimum. It is shown that this modeling technique can be a useful alternative for modeling of chromatographic responses. Copyright
PB  - Wiley-Blackwell, Hoboken
T2  - Journal of Chemometrics
T1  - Comparison of interpolation polynomials with divided differences, interpolation polynomials with finite differences, and quadratic functions obtained by the least squares method in modeling of chromatographic responses
VL  - 27
IS  - 12
SP  - 466
EP  - 474
DO  - 10.1002/cem.2559
ER  - 

@article{
author = "Rakić, Tijana and Stanimirović, Zorica and Denić, Aleksandar and Marić, Miroslav and Jančić-Stojanović, Biljana and Medenica, Mirjana",
year = "2013",
abstract = "A novel approach to mathematical modeling of chromatographic responses based on interpolation polynomials with divided differences and with finite differences is discussed. These interpolational techniques as well as traditionally applied second-order polynomial models obtained by least squares are compared. Interpolation techniques can be useful in situations where commonly used linear or quadratic models are not applicable: when the nature of dependence is complex or the investigated factor intervals are broad. The three analyzed modeling techniques are incorporated in a design of experiments methodology for systematic development and optimization of liquid chromatographic methods. The direct modeling of retention factors is carried out first, while the objective function for final quality measurement is calculated last. An interpolation polynomial with divided differences resulted in a high quality fit compared with the results obtained by the other two modeling approaches and succeeded in locating the desired optimum. It is shown that this modeling technique can be a useful alternative for modeling of chromatographic responses. Copyright",
publisher = "Wiley-Blackwell, Hoboken",
journal = "Journal of Chemometrics",
title = "Comparison of interpolation polynomials with divided differences, interpolation polynomials with finite differences, and quadratic functions obtained by the least squares method in modeling of chromatographic responses",
volume = "27",
number = "12",
pages = "466-474",
doi = "10.1002/cem.2559"
}

Rakić, T., Stanimirović, Z., Denić, A., Marić, M., Jančić-Stojanović, B.,& Medenica, M.. (2013). Comparison of interpolation polynomials with divided differences, interpolation polynomials with finite differences, and quadratic functions obtained by the least squares method in modeling of chromatographic responses. in Journal of Chemometrics
Wiley-Blackwell, Hoboken., 27(12), 466-474.
https://doi.org/10.1002/cem.2559

Rakić T, Stanimirović Z, Denić A, Marić M, Jančić-Stojanović B, Medenica M. Comparison of interpolation polynomials with divided differences, interpolation polynomials with finite differences, and quadratic functions obtained by the least squares method in modeling of chromatographic responses. in Journal of Chemometrics. 2013;27(12):466-474.
doi:10.1002/cem.2559 .

Rakić, Tijana, Stanimirović, Zorica, Denić, Aleksandar, Marić, Miroslav, Jančić-Stojanović, Biljana, Medenica, Mirjana, "Comparison of interpolation polynomials with divided differences, interpolation polynomials with finite differences, and quadratic functions obtained by the least squares method in modeling of chromatographic responses" in Journal of Chemometrics, 27, no. 12 (2013):466-474,
https://doi.org/10.1002/cem.2559 . .

TY  - JOUR
AU  - Vemić, Ana
AU  - Malenović, Anđelija
AU  - Rakić, Tijana
AU  - Kostić, Nada M.
AU  - Jančić-Stojanović, Biljana
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2012
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1681
AB  - Microemulsions when used as mobile phases represent a very powerful chromatographic tool due to their polyphase structure. The aim of this study was to investigate the influence of the mobile phase composition and resulting microemulsion droplet's properties, as well as the stationary phase lipophilicity on the chromatographic behavior of pramipexole and its five impurities. Investigation was carried out according to the experimental plan defined by a full factorial design 2(4) with four central point replications. While the most affected by column characteristics was the last eluting, most lipophilic substance, the composition and characteristics of microemulsion droplets were equally important, so the partition system microemulsion droplets/stationary phase proved to be the most significant. Stationary phase lipophilicity did not affect the most hydrophilic component and only the partition system microemulsion droplets/bulk of the eluent impacted its behavior. For the separation of the critical pair, almost equal effects of the microemulsion droplets/stationary phase and bulk of the eluent/stationary phase partition systems were noted.
PB  - Soc Brasileira Quimica, Sao Paulo
T2  - Journal of the Brazilian Chemical Society
T1  - Physicochemical Factors Governing the Partition of Pramipexole and Its Five Impurities in Microemulsion Liquid Chromatographic Systems
VL  - 23
IS  - 11
SP  - 2084
EP  - 2092
UR  - https://hdl.handle.net/21.15107/rcub_farfar_1681
ER  - 

@article{
author = "Vemić, Ana and Malenović, Anđelija and Rakić, Tijana and Kostić, Nada M. and Jančić-Stojanović, Biljana and Ivanović, Darko and Medenica, Mirjana",
year = "2012",
abstract = "Microemulsions when used as mobile phases represent a very powerful chromatographic tool due to their polyphase structure. The aim of this study was to investigate the influence of the mobile phase composition and resulting microemulsion droplet's properties, as well as the stationary phase lipophilicity on the chromatographic behavior of pramipexole and its five impurities. Investigation was carried out according to the experimental plan defined by a full factorial design 2(4) with four central point replications. While the most affected by column characteristics was the last eluting, most lipophilic substance, the composition and characteristics of microemulsion droplets were equally important, so the partition system microemulsion droplets/stationary phase proved to be the most significant. Stationary phase lipophilicity did not affect the most hydrophilic component and only the partition system microemulsion droplets/bulk of the eluent impacted its behavior. For the separation of the critical pair, almost equal effects of the microemulsion droplets/stationary phase and bulk of the eluent/stationary phase partition systems were noted.",
publisher = "Soc Brasileira Quimica, Sao Paulo",
journal = "Journal of the Brazilian Chemical Society",
title = "Physicochemical Factors Governing the Partition of Pramipexole and Its Five Impurities in Microemulsion Liquid Chromatographic Systems",
volume = "23",
number = "11",
pages = "2084-2092",
url = "https://hdl.handle.net/21.15107/rcub_farfar_1681"
}

Vemić, A., Malenović, A., Rakić, T., Kostić, N. M., Jančić-Stojanović, B., Ivanović, D.,& Medenica, M.. (2012). Physicochemical Factors Governing the Partition of Pramipexole and Its Five Impurities in Microemulsion Liquid Chromatographic Systems. in Journal of the Brazilian Chemical Society
Soc Brasileira Quimica, Sao Paulo., 23(11), 2084-2092.
https://hdl.handle.net/21.15107/rcub_farfar_1681

Vemić A, Malenović A, Rakić T, Kostić NM, Jančić-Stojanović B, Ivanović D, Medenica M. Physicochemical Factors Governing the Partition of Pramipexole and Its Five Impurities in Microemulsion Liquid Chromatographic Systems. in Journal of the Brazilian Chemical Society. 2012;23(11):2084-2092.
https://hdl.handle.net/21.15107/rcub_farfar_1681 .

Vemić, Ana, Malenović, Anđelija, Rakić, Tijana, Kostić, Nada M., Jančić-Stojanović, Biljana, Ivanović, Darko, Medenica, Mirjana, "Physicochemical Factors Governing the Partition of Pramipexole and Its Five Impurities in Microemulsion Liquid Chromatographic Systems" in Journal of the Brazilian Chemical Society, 23, no. 11 (2012):2084-2092,
https://hdl.handle.net/21.15107/rcub_farfar_1681 .

TY  - JOUR
AU  - Rakić, Tijana
AU  - Malenović, Anđelija
AU  - Jančić-Stojanović, Biljana
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2012
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1758
AB  - The algorithm of Dong and error estimation based on a priori declared negligible effects (dummy factor effects approach) were evaluated for testing robustness, in case they provide contradictory results. Robustness of LC method for separation of ropinirole and its impurity was determined. Plackett-Burman design was applied to unravel the significant/influential factors. Four selected responses (retention factor of ropinirole and impurity, selectivity and resolution) were analyzed by the standard algorithm of Dong and dummy factor effects approach. The interpretation of the results for retention factor of ropinirole and resolution was inconclusive, since the two applied approaches identified different significant factors. The potential false negative or false positive results were avoided reanalyzing the results by the modified approaches. Modification of the dummy factor effects approach included omitting the large dummy effects values, and modification of the algorithm of Dong included calculating the margin of error values for all different number of factors included, and then selecting the lowest one to be the critical effect. The applied reanalysis allowed final important factor identification and non-significant intervals for significant effects calculation.
PB  - Springer Heidelberg, Heidelberg
T2  - Chromatographia
T1  - Avoiding the False Negative Results in LC Method Robustness Testing by Modifications of the Algorithm of Dong and Dummy Factor Effects Approach
VL  - 75
IS  - 7-8
SP  - 397
EP  - 401
DO  - 10.1007/s10337-012-2196-6
ER  - 

@article{
author = "Rakić, Tijana and Malenović, Anđelija and Jančić-Stojanović, Biljana and Ivanović, Darko and Medenica, Mirjana",
year = "2012",
abstract = "The algorithm of Dong and error estimation based on a priori declared negligible effects (dummy factor effects approach) were evaluated for testing robustness, in case they provide contradictory results. Robustness of LC method for separation of ropinirole and its impurity was determined. Plackett-Burman design was applied to unravel the significant/influential factors. Four selected responses (retention factor of ropinirole and impurity, selectivity and resolution) were analyzed by the standard algorithm of Dong and dummy factor effects approach. The interpretation of the results for retention factor of ropinirole and resolution was inconclusive, since the two applied approaches identified different significant factors. The potential false negative or false positive results were avoided reanalyzing the results by the modified approaches. Modification of the dummy factor effects approach included omitting the large dummy effects values, and modification of the algorithm of Dong included calculating the margin of error values for all different number of factors included, and then selecting the lowest one to be the critical effect. The applied reanalysis allowed final important factor identification and non-significant intervals for significant effects calculation.",
publisher = "Springer Heidelberg, Heidelberg",
journal = "Chromatographia",
title = "Avoiding the False Negative Results in LC Method Robustness Testing by Modifications of the Algorithm of Dong and Dummy Factor Effects Approach",
volume = "75",
number = "7-8",
pages = "397-401",
doi = "10.1007/s10337-012-2196-6"
}

Rakić, T., Malenović, A., Jančić-Stojanović, B., Ivanović, D.,& Medenica, M.. (2012). Avoiding the False Negative Results in LC Method Robustness Testing by Modifications of the Algorithm of Dong and Dummy Factor Effects Approach. in Chromatographia
Springer Heidelberg, Heidelberg., 75(7-8), 397-401.
https://doi.org/10.1007/s10337-012-2196-6

Rakić T, Malenović A, Jančić-Stojanović B, Ivanović D, Medenica M. Avoiding the False Negative Results in LC Method Robustness Testing by Modifications of the Algorithm of Dong and Dummy Factor Effects Approach. in Chromatographia. 2012;75(7-8):397-401.
doi:10.1007/s10337-012-2196-6 .

Rakić, Tijana, Malenović, Anđelija, Jančić-Stojanović, Biljana, Ivanović, Darko, Medenica, Mirjana, "Avoiding the False Negative Results in LC Method Robustness Testing by Modifications of the Algorithm of Dong and Dummy Factor Effects Approach" in Chromatographia, 75, no. 7-8 (2012):397-401,
https://doi.org/10.1007/s10337-012-2196-6 . .

TY  - JOUR
AU  - Jovanović, Marko
AU  - Rakić, Tijana
AU  - Jančić-Stojanović, Biljana
AU  - Malenović, Anđelija
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2012
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1714
AB  - In this paper, the retention prediction models for mixture of beta-lactam antibiotics analyzed by hydrophilic interaction chromatography (HILIC) are presented. The aim of the study was to investigate the retention behavior of some organic acids and amphoteric compounds including cephalosporins (cefotaxime, cefalexin, cefaclor, cefuroxime, and cefuroxime axetil) and penicillins (ampicillin and amoxicillin). Retention of substances with acidic functional group in HILIC is considered to be interesting since the majority of publications in literature are related to basic compounds. In the beginning of the study, classical silica columns were chosen for the retention analysis. Then, preliminary study was done and factors with the most significant influence on the retention factors were selected. These factors with the impact on the retention factors were investigated employing Box-Behnken design as a tool. On the basis of the obtained results the mathematical models were created and tested using ANOVA test and finally verified. This approach enables the presentation of chromatographic retention in many ways (three-dimensional (3-D) graphs and simple two-dimensional graphical presentations). All of these gave the possibility to predict the chromatographic retention under different conditions. Furthermore, regarding the structure of the analyzed compounds, the potential retention mechanisms in HILIC were suggested.
PB  - Wiley-VCH Verlag GMBH, Weinheim
T2  - Journal of Separation Science
T1  - Assessment of beta-lactams retention in hydrophilic interaction chromatography applying Box-Behnken Design
VL  - 35
IS  - 12
SP  - 1424
EP  - 1431
DO  - 10.1002/jssc.201200099
ER  - 

@article{
author = "Jovanović, Marko and Rakić, Tijana and Jančić-Stojanović, Biljana and Malenović, Anđelija and Ivanović, Darko and Medenica, Mirjana",
year = "2012",
abstract = "In this paper, the retention prediction models for mixture of beta-lactam antibiotics analyzed by hydrophilic interaction chromatography (HILIC) are presented. The aim of the study was to investigate the retention behavior of some organic acids and amphoteric compounds including cephalosporins (cefotaxime, cefalexin, cefaclor, cefuroxime, and cefuroxime axetil) and penicillins (ampicillin and amoxicillin). Retention of substances with acidic functional group in HILIC is considered to be interesting since the majority of publications in literature are related to basic compounds. In the beginning of the study, classical silica columns were chosen for the retention analysis. Then, preliminary study was done and factors with the most significant influence on the retention factors were selected. These factors with the impact on the retention factors were investigated employing Box-Behnken design as a tool. On the basis of the obtained results the mathematical models were created and tested using ANOVA test and finally verified. This approach enables the presentation of chromatographic retention in many ways (three-dimensional (3-D) graphs and simple two-dimensional graphical presentations). All of these gave the possibility to predict the chromatographic retention under different conditions. Furthermore, regarding the structure of the analyzed compounds, the potential retention mechanisms in HILIC were suggested.",
publisher = "Wiley-VCH Verlag GMBH, Weinheim",
journal = "Journal of Separation Science",
title = "Assessment of beta-lactams retention in hydrophilic interaction chromatography applying Box-Behnken Design",
volume = "35",
number = "12",
pages = "1424-1431",
doi = "10.1002/jssc.201200099"
}

Jovanović, M., Rakić, T., Jančić-Stojanović, B., Malenović, A., Ivanović, D.,& Medenica, M.. (2012). Assessment of beta-lactams retention in hydrophilic interaction chromatography applying Box-Behnken Design. in Journal of Separation Science
Wiley-VCH Verlag GMBH, Weinheim., 35(12), 1424-1431.
https://doi.org/10.1002/jssc.201200099

Jovanović M, Rakić T, Jančić-Stojanović B, Malenović A, Ivanović D, Medenica M. Assessment of beta-lactams retention in hydrophilic interaction chromatography applying Box-Behnken Design. in Journal of Separation Science. 2012;35(12):1424-1431.
doi:10.1002/jssc.201200099 .

Jovanović, Marko, Rakić, Tijana, Jančić-Stojanović, Biljana, Malenović, Anđelija, Ivanović, Darko, Medenica, Mirjana, "Assessment of beta-lactams retention in hydrophilic interaction chromatography applying Box-Behnken Design" in Journal of Separation Science, 35, no. 12 (2012):1424-1431,
https://doi.org/10.1002/jssc.201200099 . .

TY  - JOUR
AU  - Rakić, Tijana
AU  - Jančić-Stojanović, Biljana
AU  - Malenović, Anđelija
AU  - Ivanović, Darko
AU  - Medenica, Mirjana
PY  - 2012
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1646
AB  - This paper presents a newly developed demasking large dummy effects (DDE) approach for identification of significant factor interactions in Plackett-Burman experimental design. Dummy factors, as imaginary factors, are not expected to contribute to the model, so the appearance of their high effect values could indicate the significance of the interactions they are confounded with. DDE approach consists of the screening of the large estimable effects, the calculation of the interactions that contribute the most to the large dummy effects from the alias matrix, and a single pass of all subsets regressions including preselected interactions and main factors for the final model tuning. Tested on experimentally obtained data from a robustness analysis of a method for the determination of raloxifene and its four impurities, DDE approach showed to create the models that have greater statistical power than the ones described with the main factors only, which makes them more reliable and accurate for the application. Additionally, because of the interactions selection criterion and final tuning phase of the strategy, DDE approach allows the creation of models that are likely to better describe the real systems, which increases the practical value. Copyright
PB  - Wiley, Hoboken
T2  - Journal of Chemometrics
T1  - Demasking large dummy effects approach in revealing important interactions in Plackett-Burman experimental design
VL  - 26
IS  - 10
SP  - 518
EP  - 525
DO  - 10.1002/cem.2461
ER  - 

@article{
author = "Rakić, Tijana and Jančić-Stojanović, Biljana and Malenović, Anđelija and Ivanović, Darko and Medenica, Mirjana",
year = "2012",
abstract = "This paper presents a newly developed demasking large dummy effects (DDE) approach for identification of significant factor interactions in Plackett-Burman experimental design. Dummy factors, as imaginary factors, are not expected to contribute to the model, so the appearance of their high effect values could indicate the significance of the interactions they are confounded with. DDE approach consists of the screening of the large estimable effects, the calculation of the interactions that contribute the most to the large dummy effects from the alias matrix, and a single pass of all subsets regressions including preselected interactions and main factors for the final model tuning. Tested on experimentally obtained data from a robustness analysis of a method for the determination of raloxifene and its four impurities, DDE approach showed to create the models that have greater statistical power than the ones described with the main factors only, which makes them more reliable and accurate for the application. Additionally, because of the interactions selection criterion and final tuning phase of the strategy, DDE approach allows the creation of models that are likely to better describe the real systems, which increases the practical value. Copyright",
publisher = "Wiley, Hoboken",
journal = "Journal of Chemometrics",
title = "Demasking large dummy effects approach in revealing important interactions in Plackett-Burman experimental design",
volume = "26",
number = "10",
pages = "518-525",
doi = "10.1002/cem.2461"
}

Rakić, T., Jančić-Stojanović, B., Malenović, A., Ivanović, D.,& Medenica, M.. (2012). Demasking large dummy effects approach in revealing important interactions in Plackett-Burman experimental design. in Journal of Chemometrics
Wiley, Hoboken., 26(10), 518-525.
https://doi.org/10.1002/cem.2461

Rakić T, Jančić-Stojanović B, Malenović A, Ivanović D, Medenica M. Demasking large dummy effects approach in revealing important interactions in Plackett-Burman experimental design. in Journal of Chemometrics. 2012;26(10):518-525.
doi:10.1002/cem.2461 .

Rakić, Tijana, Jančić-Stojanović, Biljana, Malenović, Anđelija, Ivanović, Darko, Medenica, Mirjana, "Demasking large dummy effects approach in revealing important interactions in Plackett-Burman experimental design" in Journal of Chemometrics, 26, no. 10 (2012):518-525,
https://doi.org/10.1002/cem.2461 . .