TY  - JOUR
AU  - Goronja, Jelena
AU  - Erić, Slavica
AU  - Malenović, Anđelija
PY  - 2019
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3317
AB  - Retention behavior of ionized and unionized forms of ten weak acid solutes was investigated in hybrid micellar systems with varying cetyltrimethylammonium bromide concentrations (CTAB), acetonitrile (ACN) content and mobile phase pH range from 2.5 to 7.5. It was shown that observed retention patterns are significantly affected by CTAB concentration, ACN volume fraction and analytes' ionization state. The rationale and quantitative description for observed retention behavior was obtained by fitting k values to retention model and calculation of binding constants for both ionized and unionized species. The importance of interaction between analyte anions and positively charged CTAB molecules adsorbed onto stationary phase surface was confirmed. For all solutes, except salicylic acid and furosemide, binding to stationary phase is reduced upon ACN volume fraction increase since the solvent partially desorbs the adsorbed surfactant. Also, the interactions of analytes with micelles are diminished with increase in ACN content because it promotes decrease in micelle aggregation number and its capacity for analyte binding. The additional analysis to identify and interpret molecular descriptors which can best explain the experimental evidence and findings obtained was performed. These findings could provide a new and specific understanding of the interactions between all the components of the hybrid micellar chromatographic system and a good basis for further investigations suggesting the development of generally applicable predictors in structure-retention relationship studies in related chromatographic systems.
PB  - Taylor & Francis Inc, Philadelphia
T2  - Journal of Liquid Chromatography & Related Technologies
T1  - Identification of the factors affecting the retention of weak acid solutes in hybrid micellar systems with cetyltrimethylammonium bromide
VL  - 42
IS  - 1-2
SP  - 45
EP  - 53
DO  - 10.1080/10826076.2019.1584568
ER  - 

@article{
author = "Goronja, Jelena and Erić, Slavica and Malenović, Anđelija",
year = "2019",
abstract = "Retention behavior of ionized and unionized forms of ten weak acid solutes was investigated in hybrid micellar systems with varying cetyltrimethylammonium bromide concentrations (CTAB), acetonitrile (ACN) content and mobile phase pH range from 2.5 to 7.5. It was shown that observed retention patterns are significantly affected by CTAB concentration, ACN volume fraction and analytes' ionization state. The rationale and quantitative description for observed retention behavior was obtained by fitting k values to retention model and calculation of binding constants for both ionized and unionized species. The importance of interaction between analyte anions and positively charged CTAB molecules adsorbed onto stationary phase surface was confirmed. For all solutes, except salicylic acid and furosemide, binding to stationary phase is reduced upon ACN volume fraction increase since the solvent partially desorbs the adsorbed surfactant. Also, the interactions of analytes with micelles are diminished with increase in ACN content because it promotes decrease in micelle aggregation number and its capacity for analyte binding. The additional analysis to identify and interpret molecular descriptors which can best explain the experimental evidence and findings obtained was performed. These findings could provide a new and specific understanding of the interactions between all the components of the hybrid micellar chromatographic system and a good basis for further investigations suggesting the development of generally applicable predictors in structure-retention relationship studies in related chromatographic systems.",
publisher = "Taylor & Francis Inc, Philadelphia",
journal = "Journal of Liquid Chromatography & Related Technologies",
title = "Identification of the factors affecting the retention of weak acid solutes in hybrid micellar systems with cetyltrimethylammonium bromide",
volume = "42",
number = "1-2",
pages = "45-53",
doi = "10.1080/10826076.2019.1584568"
}

Goronja, J., Erić, S.,& Malenović, A.. (2019). Identification of the factors affecting the retention of weak acid solutes in hybrid micellar systems with cetyltrimethylammonium bromide. in Journal of Liquid Chromatography & Related Technologies
Taylor & Francis Inc, Philadelphia., 42(1-2), 45-53.
https://doi.org/10.1080/10826076.2019.1584568

Goronja J, Erić S, Malenović A. Identification of the factors affecting the retention of weak acid solutes in hybrid micellar systems with cetyltrimethylammonium bromide. in Journal of Liquid Chromatography & Related Technologies. 2019;42(1-2):45-53.
doi:10.1080/10826076.2019.1584568 .

Goronja, Jelena, Erić, Slavica, Malenović, Anđelija, "Identification of the factors affecting the retention of weak acid solutes in hybrid micellar systems with cetyltrimethylammonium bromide" in Journal of Liquid Chromatography & Related Technologies, 42, no. 1-2 (2019):45-53,
https://doi.org/10.1080/10826076.2019.1584568 . .

TY  - JOUR
AU  - Rmandić, Milena
AU  - Dotsikas, Yannis
AU  - Malenović, Anđelija
PY  - 2019
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3325
AB  - In the present study we aimed at reaching a procedure for control of factors that have a potential to contribute to bioanalytical method bias and consistent dried blood spot (DBS) formation. The most influencing factors were identified via experimental design and image processing methodology. The effects of five qualitative factors temperature of blood samples, type of pipettes, pipetting technique, age of blood samples and analysts were investigated by multilevel categorical D-optimal design. Due to well-known influence of hematocrit (Hct) level on rheological characteristic of blood samples, five responses were observed through the study (RSD22%Hct, RSD30%Hct, RSD39%Hct, RSD51%Hct, RSD62%Hct) for their ability to provide insights into influence of factor settings onto DBS areas consistency. The area of blood spots was determined by image processing after scanning DBS cards with four spot replicates, corresponding to particular combination of investigated factors, as defined by experimental plan. The qualitative linear mathematical models with added appropriate two-factor interactions were derived by the principle of backward elimination. It was concluded that %RSD value of DBS, for all investigated Hct levels, is completely independent of type of pipettes and age of blood samples, but can significantly be affected by blood sample temperature, pipetting technique and training of analyst. Therefore, the procedure for precise and accurate formation of DBS of uniform area, regardless the Hct value, implies samples at body/room temperature, reversed pipetting technique for rigorous delivery of a sample volume onto the card and a properly trained analyst for handling samples. Finally, a verification experiment was performed and the adequacy of the suggested procedure was confirmed. Identification of the factors affecting the consistency of DBS formation provided the evidence that this contribution to total assay bias can be successfully controlled and reduced.
PB  - Elsevier Science BV, Amsterdam
T2  - Microchemical Journal
T1  - Identification of the factors affecting the consistency of DBS formation via experimental design and image processing methodology
VL  - 145
SP  - 1003
EP  - 1010
DO  - 10.1016/j.microc.2018.12.016
ER  - 

@article{
author = "Rmandić, Milena and Dotsikas, Yannis and Malenović, Anđelija",
year = "2019",
abstract = "In the present study we aimed at reaching a procedure for control of factors that have a potential to contribute to bioanalytical method bias and consistent dried blood spot (DBS) formation. The most influencing factors were identified via experimental design and image processing methodology. The effects of five qualitative factors temperature of blood samples, type of pipettes, pipetting technique, age of blood samples and analysts were investigated by multilevel categorical D-optimal design. Due to well-known influence of hematocrit (Hct) level on rheological characteristic of blood samples, five responses were observed through the study (RSD22%Hct, RSD30%Hct, RSD39%Hct, RSD51%Hct, RSD62%Hct) for their ability to provide insights into influence of factor settings onto DBS areas consistency. The area of blood spots was determined by image processing after scanning DBS cards with four spot replicates, corresponding to particular combination of investigated factors, as defined by experimental plan. The qualitative linear mathematical models with added appropriate two-factor interactions were derived by the principle of backward elimination. It was concluded that %RSD value of DBS, for all investigated Hct levels, is completely independent of type of pipettes and age of blood samples, but can significantly be affected by blood sample temperature, pipetting technique and training of analyst. Therefore, the procedure for precise and accurate formation of DBS of uniform area, regardless the Hct value, implies samples at body/room temperature, reversed pipetting technique for rigorous delivery of a sample volume onto the card and a properly trained analyst for handling samples. Finally, a verification experiment was performed and the adequacy of the suggested procedure was confirmed. Identification of the factors affecting the consistency of DBS formation provided the evidence that this contribution to total assay bias can be successfully controlled and reduced.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Microchemical Journal",
title = "Identification of the factors affecting the consistency of DBS formation via experimental design and image processing methodology",
volume = "145",
pages = "1003-1010",
doi = "10.1016/j.microc.2018.12.016"
}

Rmandić, M., Dotsikas, Y.,& Malenović, A.. (2019). Identification of the factors affecting the consistency of DBS formation via experimental design and image processing methodology. in Microchemical Journal
Elsevier Science BV, Amsterdam., 145, 1003-1010.
https://doi.org/10.1016/j.microc.2018.12.016

Rmandić M, Dotsikas Y, Malenović A. Identification of the factors affecting the consistency of DBS formation via experimental design and image processing methodology. in Microchemical Journal. 2019;145:1003-1010.
doi:10.1016/j.microc.2018.12.016 .

Rmandić, Milena, Dotsikas, Yannis, Malenović, Anđelija, "Identification of the factors affecting the consistency of DBS formation via experimental design and image processing methodology" in Microchemical Journal, 145 (2019):1003-1010,
https://doi.org/10.1016/j.microc.2018.12.016 . .

TY  - JOUR
AU  - Colović, Jelena
AU  - Rmandić, Milena
AU  - Malenović, Anđelija
PY  - 2019
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3310
AB  - In this study robust optimization was applied for the development of a reliable analytical assay for lamotrigine, its impurity A, and impurity G in tablets by chaotropic chromatography. The influence of the critical method parameters (acetonitrile content, concentration of chaotropic agent, and pH of the water phase) on the set of selected critical method attributes (retention factor of impurity A, separation factor between lamotrigine and impurity G, and retention factor of impurity G) is studied by Box-Behnken design. Monte Carlo simulations were applied to propagate the errors originating from the model coefficients' calculation to the selected responses and obtain their predictive distribution. Design space was defined (95%) and a working point selected: 23% of acetonitrile in the mobile phase, 77% of water phase containing 140mM of perchloric acid, and pH of the water phase adjusted to 2.50. Further robustness testing was performed by Plackett-Burman design to evaluate the quantitative performance of the developed method. The obtained models included not only active main effects but also interactions that were identified as active with the aid of an alias matrix approach and examination of resulting alias plots. The method was validated and its reliability for routine pharmaceutical analysis confirmed. [GRAPHICS] .
PB  - Springer Heidelberg, Heidelberg
T2  - Chromatographia
T1  - Robust Optimization of Chaotropic Chromatography Assay for Lamotrigine and its Two Impurities in Tablets
VL  - 82
IS  - 2
SP  - 565
EP  - 577
DO  - 10.1007/s10337-018-3661-7
ER  - 

@article{
author = "Colović, Jelena and Rmandić, Milena and Malenović, Anđelija",
year = "2019",
abstract = "In this study robust optimization was applied for the development of a reliable analytical assay for lamotrigine, its impurity A, and impurity G in tablets by chaotropic chromatography. The influence of the critical method parameters (acetonitrile content, concentration of chaotropic agent, and pH of the water phase) on the set of selected critical method attributes (retention factor of impurity A, separation factor between lamotrigine and impurity G, and retention factor of impurity G) is studied by Box-Behnken design. Monte Carlo simulations were applied to propagate the errors originating from the model coefficients' calculation to the selected responses and obtain their predictive distribution. Design space was defined (95%) and a working point selected: 23% of acetonitrile in the mobile phase, 77% of water phase containing 140mM of perchloric acid, and pH of the water phase adjusted to 2.50. Further robustness testing was performed by Plackett-Burman design to evaluate the quantitative performance of the developed method. The obtained models included not only active main effects but also interactions that were identified as active with the aid of an alias matrix approach and examination of resulting alias plots. The method was validated and its reliability for routine pharmaceutical analysis confirmed. [GRAPHICS] .",
publisher = "Springer Heidelberg, Heidelberg",
journal = "Chromatographia",
title = "Robust Optimization of Chaotropic Chromatography Assay for Lamotrigine and its Two Impurities in Tablets",
volume = "82",
number = "2",
pages = "565-577",
doi = "10.1007/s10337-018-3661-7"
}

Colović, J., Rmandić, M.,& Malenović, A.. (2019). Robust Optimization of Chaotropic Chromatography Assay for Lamotrigine and its Two Impurities in Tablets. in Chromatographia
Springer Heidelberg, Heidelberg., 82(2), 565-577.
https://doi.org/10.1007/s10337-018-3661-7

Colović J, Rmandić M, Malenović A. Robust Optimization of Chaotropic Chromatography Assay for Lamotrigine and its Two Impurities in Tablets. in Chromatographia. 2019;82(2):565-577.
doi:10.1007/s10337-018-3661-7 .

Colović, Jelena, Rmandić, Milena, Malenović, Anđelija, "Robust Optimization of Chaotropic Chromatography Assay for Lamotrigine and its Two Impurities in Tablets" in Chromatographia, 82, no. 2 (2019):565-577,
https://doi.org/10.1007/s10337-018-3661-7 . .

TY  - THES
AU  - Tumpa, Anja
PY  - 2019
UR  - http://nardus.mpn.gov.rs/handle/123456789/12126
UR  - http://eteze.bg.ac.rs/application/showtheses?thesesId=7251
UR  - https://fedorabg.bg.ac.rs/fedora/get/o:20996/bdef:Content/download
UR  - http://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=2048379490
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3699
AB  - Poslednju deceniju susrećemo se sa brojnim izazovima kada je u pitanju analitika različitih analita primenom tečne hromatografije hidrofilnih interakcija (eng. Hydrophilic Interaction Liquid Chromatography, HILIC). Uprkos stalnom porastu broja publikovanih radova i dalje se sa sigurnošću ne može predvideti ponašanje različitih analita u ovom sistemu hromatografije. Odgovor leži u složenosti retencionih mehanizama, te su i dalje neophodna naučna istraživanja koja omogućavaju da se ovaj hromatografski sistem detaljno prouči. Shodno tome, cilj ove doktorske disertacije bio je da se primene teorijski i empirijski modeli u cilju definisanja retencionog ponašanja strukturno sličnih analita (olanzapina i njegovih srodnih supstanci) u HILIC sistemu, kao i da se stečena znanja primene kroz odgovarajuću primenu nove metode. Ispitivana smeša analita olanzapina i njegovih osam srodnih supstanci po prvi put je ispitivana u HILIC sistemu u ovoj doktorskoj disertaciji. Pored toga, dve srodne supstance (2 i 8) predstavljaju supstance koje se po prvi put hromatografski opisuju i za koje ne postoje literaturni podaci.U okviru preliminarnih ispitivanja ispitane su četiri HILIC stacionarne faze (silika, diolna, cijano i cviterjonska) pod istim hromatografskim uslovima, čime je omogućeno donošenje preliminarnih zaključaka o uticaju fizičko-hemijskih karakteristika stacionarne faze, kao i analita na retenciono ponašanje u HILIC sistemu.U sledećoj fazi istraživanja, pristupilo se ispitivanju uticaja polarnije komponente mobilne faze (vodeni rastvor pufera), kako bi se dobile informacije o mehanizmima koji su uključeni u celokupan proces retencionog ponašanja. Izvršeno je fitovanje dobijenih rezultata retencionih vremena u teorijske (adsorpcioni, particioni, mešoviti i kvadratni model) i eksperimentalne (Neue model) matematičke modele. Za ocenu podobnosti matematičkih modela koristili su se koeficijent determinacije (R2) i unakrsno validiranikoeficijent determinacije (Q2) kao statistički parametri koji opisuju kvalitet matematičkog modela. Kako  postojeći  matematički  modeli  nisu dali  zadovoljavajuću  pogodnost,   u sledećem delu doktorske disertacije pristupilo se kreiranju splajn interpolacionog modelačija je primena za modelovanje hromatografskog ponašanja analita prvi put opisana uovoj doktorskoj  disertaciji.Izračunate vrednosti za R2i  Q2koeficijente  pokazali  su  da  splajn dobro opisuje ispitivani hromatografski sistem, kao i da se može koristiti za predviđanje retencionog ponašanja ispitivanih analita u HILIC sistemu.Nakon  teorijskih  ispitivanja  retencionih  mehanizama,  u  sledećem  delu  doktorske disertacije, za smešu olanzapina i sedam srodnih supstanci, razvijena je HILIC metoda sa UV  detekcijom  uz  gradijentno  eluiranje  u  skladu  sa  AQbD  (eng. Analytical  Quality  by Design)  konceptom.  Ovo  je  prvi  put  da  je  u naučnojliteraturi  opisana  primena  AQbD principa za razvoj gradijentne HILIC metode. Prolazeći kroz dobro definisane faze ovog naučnog  koncepta  uz  korišćenje  pogodnog  eksperimentalnog  dizajna,  kreiran  je  jasno definisan Design  Space. Konačno, odabrani su optimalni hromatografski uslovi za analizu olanzapina  i  njegovih  srodnih  supstanci  primenom  gradijentne  HILIC  metode.  Na  ovaj način razvijena metoda je validirana i primenjena za analizu odgovarajućeg farmaceutskog oblika olanzapina.Jedna  od  značajnih  prednosti  HILIC  metode  jeste  korišćenje  rastvarača kompatibilnih sa masenim detektorom. Ova prednost je iskorišćena te je u završnoj fazi ove doktorske disertacije urađen prenos metode na sistem sa masenim detektorom. Transfer  je urađen  uz  pomoć  kalkulatora  koji  je  preračunao  protok  mobilne  faze,  dužinu  trajanja analize   i   uslove   gradijenta   u   sistemu   pod   visokim   pritiskom   (UPLC,   eng. Ultra Performance   Liquid   Chromatography).   Cilj   ovog   transfera   je   bio   da   se   dobije visokoosetljiva  metoda  kojom  je  moguće  tačno  i  precizno  pratiti  promene  u  stabilnosti olanzapina  pod  uticajem  različitih  agenasa.  Konačno,  kroz  postupak  validacije  metode potvrđena je njena primenljivost za praćenje stabilnosti olanzapina.
AB  - Over the last decade, we have been facing numerous challenges regarding the analysis of different substances in HILIC (Hydrophilic Interaction Liquid Chromatography) mode. Despite constant increase in the number of published scientific papers, retention mechanisms still cannot be predicted with great certainty. The answer can be found in the complexity of retention mechanisms, which creates the need for further scientific investigations in order to better understand the system. The goal of this doctoral thesis was to apply theoretical and empirical mathematical models in order to define retention behavior of the structurally similar substances (olanzapine and its related substances), which would help us use gained knowledge for the newly created model. This specific mixture of substances was investigated for the first time in HILIC in this doctoral thesis. Furthermore, two of the related substances (2 and 8) have never been investigated in any chromatography system before.Through preliminary investigations, four HILIC columns have been tested (silica, diol, cyano-propyl and zwitterionic) under the same chromatographic conditions, which allowed us to make conclusions about the influence of physicochemical characteristics of the columns and substances on the retention behavior in HILIC.In the next phase, for the purpose of investigating retention mechanisms, the influence of the more polar component of the mobile phase (aqueous buffer solution) on the retention was investigated. Fitting of the obtained results was conducted in the theoretical (adsorption, partition, mixed and quadratic) models and experimental (Neue) models. For the statistical evaluation of the models, coefficient of determination (R2) and coefficient of prediction (Q2) were used.Since the existing mathematical models did not have sufficient level of fit, in the next phase of the study, spline interpolation model was created. Spline model has neverbeen used for the modeling of chromatographic behavior, prior to this study. Calculated R2and  Q2values  showed  a  good  fit between  spline  model  and  complex  HILIC  system, consequently  allowing  it  to  predict  retention  behavior  of  the  invenstigated  substances  in HILIC.After the theoretical part of the study, in the next phase, a HILIC method with UV detection  and  gradient  elution  was  developed  in  line  with  AQbD  (Analytical  Quality  by Design) concept, for olanzapine and its seven related substances. This is the first time that the use of AQbD concept has been published in the scientific paper for the development of the HILIC method.  Going through the well-established steps of this scientific concept and by using the adequate experimental design, Design Space was defined. At the end, optimal chromatographic  conditions  for  the  analysis  of  olanzapine  and  its  related  substances  were chosen.  This  HILIC  method  with  gradient  elution  was  furthermore  validated  and  applied for the analysis of the pharmaceutical dosage form of olanzapine. One of the greatest advantages of HILIC methods is the compatibility of the polar solvents with the massdetector. This advantage was used in the last part of this study, when previously developed HILIC method was transferred to the system coupled with mass detector.  Transfer  was  performed  using  the  calculator  which  calculated  the  new  mobile phase  rate,  the duration  of  the  analysis  and  the  gradient  conditions  for  the  UPLC  system (Ultra  Performance  Liquid  Chromatography).  The  goal  of  this  transfer  was  to  develop highly  sensitive  method  which  could  accurately  follow  stability  of  olanzapine  under different  conditions.  Finally,  after  validating  the  new  method,  it’s  applicability  as  the stability indicating method was confirmed.
PB  - Универзитет у Београду, Фармацеутски факултет
T2  - Универзитет у Београду
T1  - Teorijsko i empirijsko modelovanje retencionog ponašanja olanzapina u tečnoj hromatografiji hidrofilnih interakcija
UR  - https://hdl.handle.net/21.15107/rcub_nardus_12126
ER  - 

@phdthesis{
author = "Tumpa, Anja",
year = "2019",
abstract = "Poslednju deceniju susrećemo se sa brojnim izazovima kada je u pitanju analitika različitih analita primenom tečne hromatografije hidrofilnih interakcija (eng. Hydrophilic Interaction Liquid Chromatography, HILIC). Uprkos stalnom porastu broja publikovanih radova i dalje se sa sigurnošću ne može predvideti ponašanje različitih analita u ovom sistemu hromatografije. Odgovor leži u složenosti retencionih mehanizama, te su i dalje neophodna naučna istraživanja koja omogućavaju da se ovaj hromatografski sistem detaljno prouči. Shodno tome, cilj ove doktorske disertacije bio je da se primene teorijski i empirijski modeli u cilju definisanja retencionog ponašanja strukturno sličnih analita (olanzapina i njegovih srodnih supstanci) u HILIC sistemu, kao i da se stečena znanja primene kroz odgovarajuću primenu nove metode. Ispitivana smeša analita olanzapina i njegovih osam srodnih supstanci po prvi put je ispitivana u HILIC sistemu u ovoj doktorskoj disertaciji. Pored toga, dve srodne supstance (2 i 8) predstavljaju supstance koje se po prvi put hromatografski opisuju i za koje ne postoje literaturni podaci.U okviru preliminarnih ispitivanja ispitane su četiri HILIC stacionarne faze (silika, diolna, cijano i cviterjonska) pod istim hromatografskim uslovima, čime je omogućeno donošenje preliminarnih zaključaka o uticaju fizičko-hemijskih karakteristika stacionarne faze, kao i analita na retenciono ponašanje u HILIC sistemu.U sledećoj fazi istraživanja, pristupilo se ispitivanju uticaja polarnije komponente mobilne faze (vodeni rastvor pufera), kako bi se dobile informacije o mehanizmima koji su uključeni u celokupan proces retencionog ponašanja. Izvršeno je fitovanje dobijenih rezultata retencionih vremena u teorijske (adsorpcioni, particioni, mešoviti i kvadratni model) i eksperimentalne (Neue model) matematičke modele. Za ocenu podobnosti matematičkih modela koristili su se koeficijent determinacije (R2) i unakrsno validiranikoeficijent determinacije (Q2) kao statistički parametri koji opisuju kvalitet matematičkog modela. Kako  postojeći  matematički  modeli  nisu dali  zadovoljavajuću  pogodnost,   u sledećem delu doktorske disertacije pristupilo se kreiranju splajn interpolacionog modelačija je primena za modelovanje hromatografskog ponašanja analita prvi put opisana uovoj doktorskoj  disertaciji.Izračunate vrednosti za R2i  Q2koeficijente  pokazali  su  da  splajn dobro opisuje ispitivani hromatografski sistem, kao i da se može koristiti za predviđanje retencionog ponašanja ispitivanih analita u HILIC sistemu.Nakon  teorijskih  ispitivanja  retencionih  mehanizama,  u  sledećem  delu  doktorske disertacije, za smešu olanzapina i sedam srodnih supstanci, razvijena je HILIC metoda sa UV  detekcijom  uz  gradijentno  eluiranje  u  skladu  sa  AQbD  (eng. Analytical  Quality  by Design)  konceptom.  Ovo  je  prvi  put  da  je  u naučnojliteraturi  opisana  primena  AQbD principa za razvoj gradijentne HILIC metode. Prolazeći kroz dobro definisane faze ovog naučnog  koncepta  uz  korišćenje  pogodnog  eksperimentalnog  dizajna,  kreiran  je  jasno definisan Design  Space. Konačno, odabrani su optimalni hromatografski uslovi za analizu olanzapina  i  njegovih  srodnih  supstanci  primenom  gradijentne  HILIC  metode.  Na  ovaj način razvijena metoda je validirana i primenjena za analizu odgovarajućeg farmaceutskog oblika olanzapina.Jedna  od  značajnih  prednosti  HILIC  metode  jeste  korišćenje  rastvarača kompatibilnih sa masenim detektorom. Ova prednost je iskorišćena te je u završnoj fazi ove doktorske disertacije urađen prenos metode na sistem sa masenim detektorom. Transfer  je urađen  uz  pomoć  kalkulatora  koji  je  preračunao  protok  mobilne  faze,  dužinu  trajanja analize   i   uslove   gradijenta   u   sistemu   pod   visokim   pritiskom   (UPLC,   eng. Ultra Performance   Liquid   Chromatography).   Cilj   ovog   transfera   je   bio   da   se   dobije visokoosetljiva  metoda  kojom  je  moguće  tačno  i  precizno  pratiti  promene  u  stabilnosti olanzapina  pod  uticajem  različitih  agenasa.  Konačno,  kroz  postupak  validacije  metode potvrđena je njena primenljivost za praćenje stabilnosti olanzapina., Over the last decade, we have been facing numerous challenges regarding the analysis of different substances in HILIC (Hydrophilic Interaction Liquid Chromatography) mode. Despite constant increase in the number of published scientific papers, retention mechanisms still cannot be predicted with great certainty. The answer can be found in the complexity of retention mechanisms, which creates the need for further scientific investigations in order to better understand the system. The goal of this doctoral thesis was to apply theoretical and empirical mathematical models in order to define retention behavior of the structurally similar substances (olanzapine and its related substances), which would help us use gained knowledge for the newly created model. This specific mixture of substances was investigated for the first time in HILIC in this doctoral thesis. Furthermore, two of the related substances (2 and 8) have never been investigated in any chromatography system before.Through preliminary investigations, four HILIC columns have been tested (silica, diol, cyano-propyl and zwitterionic) under the same chromatographic conditions, which allowed us to make conclusions about the influence of physicochemical characteristics of the columns and substances on the retention behavior in HILIC.In the next phase, for the purpose of investigating retention mechanisms, the influence of the more polar component of the mobile phase (aqueous buffer solution) on the retention was investigated. Fitting of the obtained results was conducted in the theoretical (adsorption, partition, mixed and quadratic) models and experimental (Neue) models. For the statistical evaluation of the models, coefficient of determination (R2) and coefficient of prediction (Q2) were used.Since the existing mathematical models did not have sufficient level of fit, in the next phase of the study, spline interpolation model was created. Spline model has neverbeen used for the modeling of chromatographic behavior, prior to this study. Calculated R2and  Q2values  showed  a  good  fit between  spline  model  and  complex  HILIC  system, consequently  allowing  it  to  predict  retention  behavior  of  the  invenstigated  substances  in HILIC.After the theoretical part of the study, in the next phase, a HILIC method with UV detection  and  gradient  elution  was  developed  in  line  with  AQbD  (Analytical  Quality  by Design) concept, for olanzapine and its seven related substances. This is the first time that the use of AQbD concept has been published in the scientific paper for the development of the HILIC method.  Going through the well-established steps of this scientific concept and by using the adequate experimental design, Design Space was defined. At the end, optimal chromatographic  conditions  for  the  analysis  of  olanzapine  and  its  related  substances  were chosen.  This  HILIC  method  with  gradient  elution  was  furthermore  validated  and  applied for the analysis of the pharmaceutical dosage form of olanzapine. One of the greatest advantages of HILIC methods is the compatibility of the polar solvents with the massdetector. This advantage was used in the last part of this study, when previously developed HILIC method was transferred to the system coupled with mass detector.  Transfer  was  performed  using  the  calculator  which  calculated  the  new  mobile phase  rate,  the duration  of  the  analysis  and  the  gradient  conditions  for  the  UPLC  system (Ultra  Performance  Liquid  Chromatography).  The  goal  of  this  transfer  was  to  develop highly  sensitive  method  which  could  accurately  follow  stability  of  olanzapine  under different  conditions.  Finally,  after  validating  the  new  method,  it’s  applicability  as  the stability indicating method was confirmed.",
publisher = "Универзитет у Београду, Фармацеутски факултет",
journal = "Универзитет у Београду",
title = "Teorijsko i empirijsko modelovanje retencionog ponašanja olanzapina u tečnoj hromatografiji hidrofilnih interakcija",
url = "https://hdl.handle.net/21.15107/rcub_nardus_12126"
}

Tumpa, A.. (2019). Teorijsko i empirijsko modelovanje retencionog ponašanja olanzapina u tečnoj hromatografiji hidrofilnih interakcija. in Универзитет у Београду
Универзитет у Београду, Фармацеутски факултет..
https://hdl.handle.net/21.15107/rcub_nardus_12126

Tumpa A. Teorijsko i empirijsko modelovanje retencionog ponašanja olanzapina u tečnoj hromatografiji hidrofilnih interakcija. in Универзитет у Београду. 2019;.
https://hdl.handle.net/21.15107/rcub_nardus_12126 .

Tumpa, Anja, "Teorijsko i empirijsko modelovanje retencionog ponašanja olanzapina u tečnoj hromatografiji hidrofilnih interakcija" in Универзитет у Београду (2019),
https://hdl.handle.net/21.15107/rcub_nardus_12126 .

TY  - JOUR
AU  - Čolović, Jelena
AU  - Rmandić, Milena
AU  - Malenović, Anđelija
PY  - 2018
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3197
AB  - Numerous stationary phases have been developed with the aim to provide desired performances during chromatographic analysis of the basic solutes in their protonated form. In this work, the procedure for the characterization of bonded stationary phase performance, when both qualitative and quantitative chromatographic factors were varied in chaotropic chromatography, was proposed. Risperidone and its three impurities were selected as model substances, while acetonitrile content in the mobile phase (20-30%), the pH of the aqueous phase (3.00-5.00), the content of chaotropic agents in the aqueous phase (10-100 mM), type of chaotropic agent (NaClO4, CF3COONa), and stationary phase type (Zorbax Eclipse XDB, Zorbax Extend) were studied as chromatographic factors. The proposed procedure implies the combination of D-optimal experimental design, indirect modeling, and polynomial-modified Gaussian model, while grid point search method was selected for the final choice of the experimental conditions which lead to the best possible stationary phase performance for basic solutes. Good agreement between experimentally obtained chromatogram and simulated chromatogram for chosen experimental conditions (25% acetonitrile, 75 mM of NaClO4, pH 4.00 on Zorbax Eclipse XDB column) confirmed the applicability of the proposed procedure. The additional point was selected for the verification of proposed procedure ability to distinguish changes in solutes' elution order. Simulated chromatogram for 21.5% acetonitrile, 85 mM of NaClO4, pH 5.00 on Zorbax Eclipse XDB column was in line with experimental data. Furthermore, the values of left and right peak half-widths obtained from indirect modeling were used in order to evaluate performances of differently modified stationary phases applying a half-width plots approach. The results from half-width plot approach as well as from the proposed procedure indicate higher efficiency and better separation performance of the stationary phase extra densely bonded and double end-capped with trimethylsilyl group than the stationary phase with the combination of end-capping and bidentate silane bonding for chromatographic analysis of basic solutes in RP-HPLC systems with chaotropic agents.
PB  - Springer Heidelberg, Heidelberg
T2  - Analytical and Bioanalytical Chemistry
T1  - Characterization of bonded stationary phase performance as a function of qualitative and quantitative chromatographic factors in chaotropic chromatography with risperidone and its impurities as model substances
VL  - 410
IS  - 20
SP  - 4855
EP  - 4866
DO  - 10.1007/s00216-018-1122-7
ER  - 

@article{
author = "Čolović, Jelena and Rmandić, Milena and Malenović, Anđelija",
year = "2018",
abstract = "Numerous stationary phases have been developed with the aim to provide desired performances during chromatographic analysis of the basic solutes in their protonated form. In this work, the procedure for the characterization of bonded stationary phase performance, when both qualitative and quantitative chromatographic factors were varied in chaotropic chromatography, was proposed. Risperidone and its three impurities were selected as model substances, while acetonitrile content in the mobile phase (20-30%), the pH of the aqueous phase (3.00-5.00), the content of chaotropic agents in the aqueous phase (10-100 mM), type of chaotropic agent (NaClO4, CF3COONa), and stationary phase type (Zorbax Eclipse XDB, Zorbax Extend) were studied as chromatographic factors. The proposed procedure implies the combination of D-optimal experimental design, indirect modeling, and polynomial-modified Gaussian model, while grid point search method was selected for the final choice of the experimental conditions which lead to the best possible stationary phase performance for basic solutes. Good agreement between experimentally obtained chromatogram and simulated chromatogram for chosen experimental conditions (25% acetonitrile, 75 mM of NaClO4, pH 4.00 on Zorbax Eclipse XDB column) confirmed the applicability of the proposed procedure. The additional point was selected for the verification of proposed procedure ability to distinguish changes in solutes' elution order. Simulated chromatogram for 21.5% acetonitrile, 85 mM of NaClO4, pH 5.00 on Zorbax Eclipse XDB column was in line with experimental data. Furthermore, the values of left and right peak half-widths obtained from indirect modeling were used in order to evaluate performances of differently modified stationary phases applying a half-width plots approach. The results from half-width plot approach as well as from the proposed procedure indicate higher efficiency and better separation performance of the stationary phase extra densely bonded and double end-capped with trimethylsilyl group than the stationary phase with the combination of end-capping and bidentate silane bonding for chromatographic analysis of basic solutes in RP-HPLC systems with chaotropic agents.",
publisher = "Springer Heidelberg, Heidelberg",
journal = "Analytical and Bioanalytical Chemistry",
title = "Characterization of bonded stationary phase performance as a function of qualitative and quantitative chromatographic factors in chaotropic chromatography with risperidone and its impurities as model substances",
volume = "410",
number = "20",
pages = "4855-4866",
doi = "10.1007/s00216-018-1122-7"
}

Čolović, J., Rmandić, M.,& Malenović, A.. (2018). Characterization of bonded stationary phase performance as a function of qualitative and quantitative chromatographic factors in chaotropic chromatography with risperidone and its impurities as model substances. in Analytical and Bioanalytical Chemistry
Springer Heidelberg, Heidelberg., 410(20), 4855-4866.
https://doi.org/10.1007/s00216-018-1122-7

Čolović J, Rmandić M, Malenović A. Characterization of bonded stationary phase performance as a function of qualitative and quantitative chromatographic factors in chaotropic chromatography with risperidone and its impurities as model substances. in Analytical and Bioanalytical Chemistry. 2018;410(20):4855-4866.
doi:10.1007/s00216-018-1122-7 .

Čolović, Jelena, Rmandić, Milena, Malenović, Anđelija, "Characterization of bonded stationary phase performance as a function of qualitative and quantitative chromatographic factors in chaotropic chromatography with risperidone and its impurities as model substances" in Analytical and Bioanalytical Chemistry, 410, no. 20 (2018):4855-4866,
https://doi.org/10.1007/s00216-018-1122-7 . .

TY  - CONF
AU  - Janošević-Ležaić, Aleksandra
AU  - Pavun, Leposava
AU  - Đikanović, Danijela
AU  - Goronja, Jelena
AU  - Pejić, Nataša
PY  - 2018
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/5217
AB  - ABSTRACT  Aggregation of the cationic surfactant cetyltrimethylammonium bromide 
(CTAB) in water (W) and acetonitrile-water (ACN-W) mixtures of different 
composition (10-20% (v/v) of ACN) was studied through fluorescence 
measurements. The CTAB critical micellar concentration (CMC) and the 
micelle aggregation number (Nagg) were determined at T = 22.0 °C. It was 
found that for increasing volume ratios of ACN to W, the CMC value attains 
a minimum (1.22 mM) at 15% (v/v) ACN while Nagg is continuously 
decreasing as ACN content in the ACN-W mixture increases. The effect of 
this dipolar aprotic solvent on the CTAB micelle formation can be interpreted 
in terms of its considerably hydrogen bonding ability and influence on balk phase properties (solvophobic effect).
PB  - Society of Physical Chemists of Serbia
C3  - Physical Chemistry 2018 (Proceedings) 14th International Conference  on Fundamental and Applied Aspects of  Physical Chemistry
T1  - Fluorimetric studies of micellar properties of cetyltrimethylammonium bromide in acetonitrile-water mixture
VL  - II
SP  - 867
EP  - 870
UR  - https://hdl.handle.net/21.15107/rcub_farfar_5217
ER  - 

@conference{
author = "Janošević-Ležaić, Aleksandra and Pavun, Leposava and Đikanović, Danijela and Goronja, Jelena and Pejić, Nataša",
year = "2018",
abstract = "ABSTRACT  Aggregation of the cationic surfactant cetyltrimethylammonium bromide 
(CTAB) in water (W) and acetonitrile-water (ACN-W) mixtures of different 
composition (10-20% (v/v) of ACN) was studied through fluorescence 
measurements. The CTAB critical micellar concentration (CMC) and the 
micelle aggregation number (Nagg) were determined at T = 22.0 °C. It was 
found that for increasing volume ratios of ACN to W, the CMC value attains 
a minimum (1.22 mM) at 15% (v/v) ACN while Nagg is continuously 
decreasing as ACN content in the ACN-W mixture increases. The effect of 
this dipolar aprotic solvent on the CTAB micelle formation can be interpreted 
in terms of its considerably hydrogen bonding ability and influence on balk phase properties (solvophobic effect).",
publisher = "Society of Physical Chemists of Serbia",
journal = "Physical Chemistry 2018 (Proceedings) 14th International Conference  on Fundamental and Applied Aspects of  Physical Chemistry",
title = "Fluorimetric studies of micellar properties of cetyltrimethylammonium bromide in acetonitrile-water mixture",
volume = "II",
pages = "867-870",
url = "https://hdl.handle.net/21.15107/rcub_farfar_5217"
}

Janošević-Ležaić, A., Pavun, L., Đikanović, D., Goronja, J.,& Pejić, N.. (2018). Fluorimetric studies of micellar properties of cetyltrimethylammonium bromide in acetonitrile-water mixture. in Physical Chemistry 2018 (Proceedings) 14th International Conference  on Fundamental and Applied Aspects of  Physical Chemistry
Society of Physical Chemists of Serbia., II, 867-870.
https://hdl.handle.net/21.15107/rcub_farfar_5217

Janošević-Ležaić A, Pavun L, Đikanović D, Goronja J, Pejić N. Fluorimetric studies of micellar properties of cetyltrimethylammonium bromide in acetonitrile-water mixture. in Physical Chemistry 2018 (Proceedings) 14th International Conference  on Fundamental and Applied Aspects of  Physical Chemistry. 2018;II:867-870.
https://hdl.handle.net/21.15107/rcub_farfar_5217 .

Janošević-Ležaić, Aleksandra, Pavun, Leposava, Đikanović, Danijela, Goronja, Jelena, Pejić, Nataša, "Fluorimetric studies of micellar properties of cetyltrimethylammonium bromide in acetonitrile-water mixture" in Physical Chemistry 2018 (Proceedings) 14th International Conference  on Fundamental and Applied Aspects of  Physical Chemistry, II (2018):867-870,
https://hdl.handle.net/21.15107/rcub_farfar_5217 .

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  - Kasagić-Vujanović, Irena
AU  - Jančić-Stojanović, Biljana
AU  - Ivanović, Darko
PY  - 2018
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3041
AB  - Using theoretical models, retention mechanisms of amlodipine besilate and its impurities D, E, and F were tested, as well as bisoprolol fumarate and its impurities A, C, K, and L. Appropriate theoretical retention models for tested compounds were used, which enabled the determination of retention mechanisms responsible for the separation of tested compounds on three different HILIC column: silica, amino, and diol. In order to describe the effect of ratio of aqueous and organic portion of the mobile phase on the retention behavior of tested compounds, as well as the consideration of shares of partition and adsorption processes in HILIC retention mechanism in all three columns, partitioning and adsorption retention theoretical models were calculated. For this purpose, the water content was varied in the range from 4% to 29%, corresponding to the HILIC region of mobile phase composition. During the experiment, values of other factors of mobile phase were maintained at a constant level. Regression coefficients of partition and adsorption retention models and the corresponding determination coefficients were determined (R-2). Partitioning models for all tested compounds on amino column had higher R-2 values, while adsorption models for all compounds tested on silica and diol column had higher R-2 value. [GRAPHICS] .
PB  - Taylor & Francis Inc, Philadelphia
T2  - Journal of Liquid Chromatography & Related Technologies
T1  - Investigation of the retention mechanisms of amlodipine besylate, bisoprolol fumarate, and their impurities on three different HILIC columns
VL  - 41
IS  - 9
SP  - 523
EP  - 531
DO  - 10.1080/10826076.2018.1476380
ER  - 

@article{
author = "Kasagić-Vujanović, Irena and Jančić-Stojanović, Biljana and Ivanović, Darko",
year = "2018",
abstract = "Using theoretical models, retention mechanisms of amlodipine besilate and its impurities D, E, and F were tested, as well as bisoprolol fumarate and its impurities A, C, K, and L. Appropriate theoretical retention models for tested compounds were used, which enabled the determination of retention mechanisms responsible for the separation of tested compounds on three different HILIC column: silica, amino, and diol. In order to describe the effect of ratio of aqueous and organic portion of the mobile phase on the retention behavior of tested compounds, as well as the consideration of shares of partition and adsorption processes in HILIC retention mechanism in all three columns, partitioning and adsorption retention theoretical models were calculated. For this purpose, the water content was varied in the range from 4% to 29%, corresponding to the HILIC region of mobile phase composition. During the experiment, values of other factors of mobile phase were maintained at a constant level. Regression coefficients of partition and adsorption retention models and the corresponding determination coefficients were determined (R-2). Partitioning models for all tested compounds on amino column had higher R-2 values, while adsorption models for all compounds tested on silica and diol column had higher R-2 value. [GRAPHICS] .",
publisher = "Taylor & Francis Inc, Philadelphia",
journal = "Journal of Liquid Chromatography & Related Technologies",
title = "Investigation of the retention mechanisms of amlodipine besylate, bisoprolol fumarate, and their impurities on three different HILIC columns",
volume = "41",
number = "9",
pages = "523-531",
doi = "10.1080/10826076.2018.1476380"
}

Kasagić-Vujanović, I., Jančić-Stojanović, B.,& Ivanović, D.. (2018). Investigation of the retention mechanisms of amlodipine besylate, bisoprolol fumarate, and their impurities on three different HILIC columns. in Journal of Liquid Chromatography & Related Technologies
Taylor & Francis Inc, Philadelphia., 41(9), 523-531.
https://doi.org/10.1080/10826076.2018.1476380

Kasagić-Vujanović I, Jančić-Stojanović B, Ivanović D. Investigation of the retention mechanisms of amlodipine besylate, bisoprolol fumarate, and their impurities on three different HILIC columns. in Journal of Liquid Chromatography & Related Technologies. 2018;41(9):523-531.
doi:10.1080/10826076.2018.1476380 .

Kasagić-Vujanović, Irena, Jančić-Stojanović, Biljana, Ivanović, Darko, "Investigation of the retention mechanisms of amlodipine besylate, bisoprolol fumarate, and their impurities on three different HILIC columns" in Journal of Liquid Chromatography & Related Technologies, 41, no. 9 (2018):523-531,
https://doi.org/10.1080/10826076.2018.1476380 . .

TY  - JOUR
AU  - Colović, Jelena
AU  - Kalinić, Marko
AU  - Vemić, Ana
AU  - Erić, Slavica
AU  - Malenović, Anđelija
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2807
AB  - In this study, we present novel insights into the pH-dependent retention behavior of protonated basic solutes in chaotropic chromatography. To this end, two sets of experiments were performed to distinguish between mobile phase pH and ionic strength effects. In the first set, the ionic strength (I) was varied with the concentration of NaPF6 and additives that adjusted the mobile phase pH, while in the second set, I was kept constant by adding the appropriate amount of NaCl. In each set, the retention behavior of 13 analytes was qualitatively examined in 21 chromatographic systems, which were defined by the NaPF6 concentration in their aqueous phases (1-50 mM) and the pH of their mobile phases (2,3 or 4); the acetonitrile content was fixed at 40%. The addition of NaCl significantly reduced the differences among retention factors at studied pH values due to the effect of the Na+ ions on PF6- adsorption to the stationary phase and the magnitude of the consequential development of the surface potential. A quantitative description of the observed phenomenon was obtained by an extended thermodynamic approach. The contribution of ion-pair formation in the stationary phase to the retention of the solutes was confirmed across models at the studied pH values in the set with varying I In the systems with a constant I, the shielding effect of the Na+ ions on the surface charge lowered the attractive surface potential and diminished the aforementioned interactions and hence the effect of the mobile phase pH on analyte retention. Eventually, we developed a readily interpretable empirical retention model that simultaneously takes into account analyte molecular structures and the most relevant chromatographic factors. Its coefficients have clear physical meaning, and owing to its good predictive capabilities, the model could be successfully used to clarify the contributions of analyte molecular structures and chromatographic factors to the specific processes underlying separation in chaotropic chromatography.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Chromatography A
T1  - Influence of the mobile phase and molecular structure parameters on the retention behavior of protonated basic solutes in chaotropic chromatography
VL  - 1511
SP  - 68
EP  - 76
DO  - 10.1016/j.chroma.2017.06.069
ER  - 

@article{
author = "Colović, Jelena and Kalinić, Marko and Vemić, Ana and Erić, Slavica and Malenović, Anđelija",
year = "2017",
abstract = "In this study, we present novel insights into the pH-dependent retention behavior of protonated basic solutes in chaotropic chromatography. To this end, two sets of experiments were performed to distinguish between mobile phase pH and ionic strength effects. In the first set, the ionic strength (I) was varied with the concentration of NaPF6 and additives that adjusted the mobile phase pH, while in the second set, I was kept constant by adding the appropriate amount of NaCl. In each set, the retention behavior of 13 analytes was qualitatively examined in 21 chromatographic systems, which were defined by the NaPF6 concentration in their aqueous phases (1-50 mM) and the pH of their mobile phases (2,3 or 4); the acetonitrile content was fixed at 40%. The addition of NaCl significantly reduced the differences among retention factors at studied pH values due to the effect of the Na+ ions on PF6- adsorption to the stationary phase and the magnitude of the consequential development of the surface potential. A quantitative description of the observed phenomenon was obtained by an extended thermodynamic approach. The contribution of ion-pair formation in the stationary phase to the retention of the solutes was confirmed across models at the studied pH values in the set with varying I In the systems with a constant I, the shielding effect of the Na+ ions on the surface charge lowered the attractive surface potential and diminished the aforementioned interactions and hence the effect of the mobile phase pH on analyte retention. Eventually, we developed a readily interpretable empirical retention model that simultaneously takes into account analyte molecular structures and the most relevant chromatographic factors. Its coefficients have clear physical meaning, and owing to its good predictive capabilities, the model could be successfully used to clarify the contributions of analyte molecular structures and chromatographic factors to the specific processes underlying separation in chaotropic chromatography.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Chromatography A",
title = "Influence of the mobile phase and molecular structure parameters on the retention behavior of protonated basic solutes in chaotropic chromatography",
volume = "1511",
pages = "68-76",
doi = "10.1016/j.chroma.2017.06.069"
}

Colović, J., Kalinić, M., Vemić, A., Erić, S.,& Malenović, A.. (2017). Influence of the mobile phase and molecular structure parameters on the retention behavior of protonated basic solutes in chaotropic chromatography. in Journal of Chromatography A
Elsevier Science BV, Amsterdam., 1511, 68-76.
https://doi.org/10.1016/j.chroma.2017.06.069

Colović J, Kalinić M, Vemić A, Erić S, Malenović A. Influence of the mobile phase and molecular structure parameters on the retention behavior of protonated basic solutes in chaotropic chromatography. in Journal of Chromatography A. 2017;1511:68-76.
doi:10.1016/j.chroma.2017.06.069 .

Colović, Jelena, Kalinić, Marko, Vemić, Ana, Erić, Slavica, Malenović, Anđelija, "Influence of the mobile phase and molecular structure parameters on the retention behavior of protonated basic solutes in chaotropic chromatography" in Journal of Chromatography A, 1511 (2017):68-76,
https://doi.org/10.1016/j.chroma.2017.06.069 . .

TY  - JOUR
AU  - Milošević, Nenad
AU  - Vemić, Ana
AU  - Colović, Jelena
AU  - Kostić, Nada
AU  - Malenović, Anđelija
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3004
AB  - The quality by design approach has been applied to develop a chaotropic chromatography method for determination of trimetazidine dihydrochloride (TMZ) and two impurities (Y-145, Y-234). Baseline separation and accurate determination of the investigated analytes was set as the target analytical profile, with k (Y-145), k (TMZ), and alpha (Y-145/TMZ) selected as critical quality attributes. The critical process parameters studied in this research were pH of water phase, acetonitrile content in mobile phase, and concentration of perchloric acid in water phase. To compute a design space as a region of the knowledge space having satisfactory values of all critical quality attributes at the desired quality level, Monte Carlo simulations were performed to propagate the error originating from the calculated model coefficients to the predicted responses. At each of 4851 defined grid points, 5000 iterations were performed and the region having probability pi ae lt yen> 95% of achieving all defined critical quality attributes was computed. A working point situated in the center of the design space was chosen, corresponding to 27% acetonitrile in mobile phase, 63% 170 mM perchloric acid in water phase, and pH of water phase adjusted to 3.60. The method was validated to confirm its reliability for use in routine pharmaceutical analysis.
PB  - Springer Heidelberg, Heidelberg
T2  - Chromatographia
T1  - Design of Experiments-Design Space Approach for Development of Chaotropic Chromatography Method for Determination of Trimetazidine Dihydrochloride and Two Impurities
VL  - 80
IS  - 4
SP  - 585
EP  - 592
DO  - 10.1007/s10337-017-3275-5
ER  - 

@article{
author = "Milošević, Nenad and Vemić, Ana and Colović, Jelena and Kostić, Nada and Malenović, Anđelija",
year = "2017",
abstract = "The quality by design approach has been applied to develop a chaotropic chromatography method for determination of trimetazidine dihydrochloride (TMZ) and two impurities (Y-145, Y-234). Baseline separation and accurate determination of the investigated analytes was set as the target analytical profile, with k (Y-145), k (TMZ), and alpha (Y-145/TMZ) selected as critical quality attributes. The critical process parameters studied in this research were pH of water phase, acetonitrile content in mobile phase, and concentration of perchloric acid in water phase. To compute a design space as a region of the knowledge space having satisfactory values of all critical quality attributes at the desired quality level, Monte Carlo simulations were performed to propagate the error originating from the calculated model coefficients to the predicted responses. At each of 4851 defined grid points, 5000 iterations were performed and the region having probability pi ae lt yen> 95% of achieving all defined critical quality attributes was computed. A working point situated in the center of the design space was chosen, corresponding to 27% acetonitrile in mobile phase, 63% 170 mM perchloric acid in water phase, and pH of water phase adjusted to 3.60. The method was validated to confirm its reliability for use in routine pharmaceutical analysis.",
publisher = "Springer Heidelberg, Heidelberg",
journal = "Chromatographia",
title = "Design of Experiments-Design Space Approach for Development of Chaotropic Chromatography Method for Determination of Trimetazidine Dihydrochloride and Two Impurities",
volume = "80",
number = "4",
pages = "585-592",
doi = "10.1007/s10337-017-3275-5"
}

Milošević, N., Vemić, A., Colović, J., Kostić, N.,& Malenović, A.. (2017). Design of Experiments-Design Space Approach for Development of Chaotropic Chromatography Method for Determination of Trimetazidine Dihydrochloride and Two Impurities. in Chromatographia
Springer Heidelberg, Heidelberg., 80(4), 585-592.
https://doi.org/10.1007/s10337-017-3275-5

Milošević N, Vemić A, Colović J, Kostić N, Malenović A. Design of Experiments-Design Space Approach for Development of Chaotropic Chromatography Method for Determination of Trimetazidine Dihydrochloride and Two Impurities. in Chromatographia. 2017;80(4):585-592.
doi:10.1007/s10337-017-3275-5 .

Milošević, Nenad, Vemić, Ana, Colović, Jelena, Kostić, Nada, Malenović, Anđelija, "Design of Experiments-Design Space Approach for Development of Chaotropic Chromatography Method for Determination of Trimetazidine Dihydrochloride and Two Impurities" in Chromatographia, 80, no. 4 (2017):585-592,
https://doi.org/10.1007/s10337-017-3275-5 . .

TY  - JOUR
AU  - Terzić, Jelena
AU  - Popović, Igor
AU  - Tumpa, Anja
AU  - Stajić, Ana
AU  - Jančić-Stojanović, Biljana
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3022
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method (vol 125, pg 385, 2016)
VL  - 138
SP  - 386
EP  - 386
DO  - 10.1016/j.jpba.2017.02.016
ER  - 

@article{
author = "Terzić, Jelena and Popović, Igor and Tumpa, Anja and Stajić, Ana and Jančić-Stojanović, Biljana",
year = "2017",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method (vol 125, pg 385, 2016)",
volume = "138",
pages = "386-386",
doi = "10.1016/j.jpba.2017.02.016"
}

Terzić, J., Popović, I., Tumpa, A., Stajić, A.,& Jančić-Stojanović, B.. (2017). Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method (vol 125, pg 385, 2016). in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 138, 386-386.
https://doi.org/10.1016/j.jpba.2017.02.016

Terzić J, Popović I, Tumpa A, Stajić A, Jančić-Stojanović B. Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method (vol 125, pg 385, 2016). in Journal of Pharmaceutical and Biomedical Analysis. 2017;138:386-386.
doi:10.1016/j.jpba.2017.02.016 .

Terzić, Jelena, Popović, Igor, Tumpa, Anja, Stajić, Ana, Jančić-Stojanović, Biljana, "Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method (vol 125, pg 385, 2016)" in Journal of Pharmaceutical and Biomedical Analysis, 138 (2017):386-386,
https://doi.org/10.1016/j.jpba.2017.02.016 . .

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  - Stajić, Ana
AU  - Jančić-Stojanović, Biljana
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2935
AB  - Background. Teicoplanin and vancomycin are glycopeptide antibiotics currently in use for treatment of multidrug-resistant bacterial infections. Scope and Approach. Severe undesirable effects, such as ototoxicity, nephrotoxicity and neutropenia have been reported for vancomycin and teicoplanin, which necessitates monitoring the concentration of these two drugs in different biological samples. In order to obtain precise and accurate results, sensitive, reliable and fast methods are necessary. The main aim of this mini review is to give a clear and concise overview of the recently developed, validated, novel and improved methods for glycopeptide antibiotic analyses in various biological matrices. Also, the variability of the matrices requires optimal and effective sample preparation procedures to be developed, and so these are discussed. Key Findings and Conclusions. Different liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods have been described for quantitative determination of glycopeptide antibiotics in various biological matrices. It was shown that protein precipitation was a convenient method for sample preparation despite the high number of novel sample preparation methods.
AB  - Uvod. Teikoplanin i vankomicin su antibiotici glikopeptidne strukture koji se trenutno koriste u terapiji multirezistentnih bakterijskih infekcija. Cilj i pristup. Ozbiljni neželjeni efekti vankomicina i teikoplanina kao što su ototoksičnost, nefrotoksičnost i neutropenija zahtevaju njihovo praćenje u različitim tipovima biološkog materijala. Osetljiva, pouzdana i brza metoda potrebna je u cilju dobijanja tačnih i preciznih podataka o koncentraciji pomenutih jedinjenja. Cilj ovog pregleda je da da jasan i kratak prikaz o razvijenim i validiranim novim, ili unapređenim metodama za analizu glikopeptidnih antibiotika u različitim biološkim matriksima. Takođe, u radu su opisane i metode pripreme uzorka upravo zbog raznovrsnosti biološkog materijala. Ključni nalazi i zaključak. Opisane su raznovrsne LC-MS/MS metode za određivanje glikopeptidnih antibiotika u biološkom materijalu. Primećeno je da je precipitacija proteina pogodna metoda pripreme uzorka bez obzira na broj novijih metoda pripreme koje se koriste.
PB  - Univerzitet u Beogradu - Fakultet veterinarske medicine, Beograd
T2  - Veterinarski glasnik
T1  - Overview of the analytical methods for vancomycin and/or teicoplanin determination in biological matrices
T1  - Pregled analitičkih metoda za određivanje vankomicina i teikoplanina u biološkom materijalu
VL  - 71
IS  - 2
SP  - 87
EP  - 97
DO  - 10.2298/VETGL1702087S
ER  - 

@article{
author = "Stajić, Ana and Jančić-Stojanović, Biljana",
year = "2017",
abstract = "Background. Teicoplanin and vancomycin are glycopeptide antibiotics currently in use for treatment of multidrug-resistant bacterial infections. Scope and Approach. Severe undesirable effects, such as ototoxicity, nephrotoxicity and neutropenia have been reported for vancomycin and teicoplanin, which necessitates monitoring the concentration of these two drugs in different biological samples. In order to obtain precise and accurate results, sensitive, reliable and fast methods are necessary. The main aim of this mini review is to give a clear and concise overview of the recently developed, validated, novel and improved methods for glycopeptide antibiotic analyses in various biological matrices. Also, the variability of the matrices requires optimal and effective sample preparation procedures to be developed, and so these are discussed. Key Findings and Conclusions. Different liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods have been described for quantitative determination of glycopeptide antibiotics in various biological matrices. It was shown that protein precipitation was a convenient method for sample preparation despite the high number of novel sample preparation methods., Uvod. Teikoplanin i vankomicin su antibiotici glikopeptidne strukture koji se trenutno koriste u terapiji multirezistentnih bakterijskih infekcija. Cilj i pristup. Ozbiljni neželjeni efekti vankomicina i teikoplanina kao što su ototoksičnost, nefrotoksičnost i neutropenija zahtevaju njihovo praćenje u različitim tipovima biološkog materijala. Osetljiva, pouzdana i brza metoda potrebna je u cilju dobijanja tačnih i preciznih podataka o koncentraciji pomenutih jedinjenja. Cilj ovog pregleda je da da jasan i kratak prikaz o razvijenim i validiranim novim, ili unapređenim metodama za analizu glikopeptidnih antibiotika u različitim biološkim matriksima. Takođe, u radu su opisane i metode pripreme uzorka upravo zbog raznovrsnosti biološkog materijala. Ključni nalazi i zaključak. Opisane su raznovrsne LC-MS/MS metode za određivanje glikopeptidnih antibiotika u biološkom materijalu. Primećeno je da je precipitacija proteina pogodna metoda pripreme uzorka bez obzira na broj novijih metoda pripreme koje se koriste.",
publisher = "Univerzitet u Beogradu - Fakultet veterinarske medicine, Beograd",
journal = "Veterinarski glasnik",
title = "Overview of the analytical methods for vancomycin and/or teicoplanin determination in biological matrices, Pregled analitičkih metoda za određivanje vankomicina i teikoplanina u biološkom materijalu",
volume = "71",
number = "2",
pages = "87-97",
doi = "10.2298/VETGL1702087S"
}

Stajić, A.,& Jančić-Stojanović, B.. (2017). Overview of the analytical methods for vancomycin and/or teicoplanin determination in biological matrices. in Veterinarski glasnik
Univerzitet u Beogradu - Fakultet veterinarske medicine, Beograd., 71(2), 87-97.
https://doi.org/10.2298/VETGL1702087S

Stajić A, Jančić-Stojanović B. Overview of the analytical methods for vancomycin and/or teicoplanin determination in biological matrices. in Veterinarski glasnik. 2017;71(2):87-97.
doi:10.2298/VETGL1702087S .

Stajić, Ana, Jančić-Stojanović, Biljana, "Overview of the analytical methods for vancomycin and/or teicoplanin determination in biological matrices" in Veterinarski glasnik, 71, no. 2 (2017):87-97,
https://doi.org/10.2298/VETGL1702087S . .

TY  - JOUR
AU  - Stajić, Ana
AU  - Anđelković, Marija
AU  - Dikić, Nenad
AU  - Rasić, J.
AU  - Vukašinović-Vesić, Milica
AU  - Ivanović, D.
AU  - Jančić-Stojanović, Biljana
PY  - 2017
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2869
AB  - From 1st January 2017 higenamine was added on the WADA (World Anti-doping Agency) Prohibited list under S3 group beta-2 agonists as at all times banned substance for the athletes. The main origine of higenamine (or norcoclaurine) are different plants including Nandina domestica, Aconitum carmichaelii, Asarum heterotropioides, Galium divaricatum, Annona squamosa, Nelumbo nucifera etc. Higenamine main use is related to weight loss and it could be found (un)labeled in different dietary supplements. The objective of this study was development of sensitive and reliable UHPLC/MS/MS method for determination of higenamine in various dietary supplement samples. In order to obtain high method sensitivity, hydrophilic interaction liquid chromatography (HILIC) mode was applied. Separation was carried out on UHPLC Acquity BEH HILIC analytical column (2.1 mm x 100 mm, 1.7 mu m particle size). Mobile phase consisted of 0.1% formic acid in water and acetonitrile, respectively, was mixed in ratio of 30:70, v/v. Flow rate was set at 0.2 mL min(-1). Quercetin was used as an internal standard. ESI (+) source ionization mode using multi reaction monitoring (MRM) mode was utilized and three ion transitions of higenamine were followed 272.08 -> 107.01, 272.08 -> 161.07 and 272.08 -> 77.08. Developed method was fully validated and applied for identification and quantification of higenamine in different dietary supplements. According to the results, the most of investigated supplements were free of higenamine, and on the other hand, presence of higenamine was confirmed in some samples while it was not declared on the label.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Determination of higenamine in dietary supplements by UHPLC/MS/MS method
VL  - 146
SP  - 48
EP  - 52
DO  - 10.1016/j.jpba.2017.08.017
ER  - 

@article{
author = "Stajić, Ana and Anđelković, Marija and Dikić, Nenad and Rasić, J. and Vukašinović-Vesić, Milica and Ivanović, D. and Jančić-Stojanović, Biljana",
year = "2017",
abstract = "From 1st January 2017 higenamine was added on the WADA (World Anti-doping Agency) Prohibited list under S3 group beta-2 agonists as at all times banned substance for the athletes. The main origine of higenamine (or norcoclaurine) are different plants including Nandina domestica, Aconitum carmichaelii, Asarum heterotropioides, Galium divaricatum, Annona squamosa, Nelumbo nucifera etc. Higenamine main use is related to weight loss and it could be found (un)labeled in different dietary supplements. The objective of this study was development of sensitive and reliable UHPLC/MS/MS method for determination of higenamine in various dietary supplement samples. In order to obtain high method sensitivity, hydrophilic interaction liquid chromatography (HILIC) mode was applied. Separation was carried out on UHPLC Acquity BEH HILIC analytical column (2.1 mm x 100 mm, 1.7 mu m particle size). Mobile phase consisted of 0.1% formic acid in water and acetonitrile, respectively, was mixed in ratio of 30:70, v/v. Flow rate was set at 0.2 mL min(-1). Quercetin was used as an internal standard. ESI (+) source ionization mode using multi reaction monitoring (MRM) mode was utilized and three ion transitions of higenamine were followed 272.08 -> 107.01, 272.08 -> 161.07 and 272.08 -> 77.08. Developed method was fully validated and applied for identification and quantification of higenamine in different dietary supplements. According to the results, the most of investigated supplements were free of higenamine, and on the other hand, presence of higenamine was confirmed in some samples while it was not declared on the label.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Determination of higenamine in dietary supplements by UHPLC/MS/MS method",
volume = "146",
pages = "48-52",
doi = "10.1016/j.jpba.2017.08.017"
}

Stajić, A., Anđelković, M., Dikić, N., Rasić, J., Vukašinović-Vesić, M., Ivanović, D.,& Jančić-Stojanović, B.. (2017). Determination of higenamine in dietary supplements by UHPLC/MS/MS method. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 146, 48-52.
https://doi.org/10.1016/j.jpba.2017.08.017

Stajić A, Anđelković M, Dikić N, Rasić J, Vukašinović-Vesić M, Ivanović D, Jančić-Stojanović B. Determination of higenamine in dietary supplements by UHPLC/MS/MS method. in Journal of Pharmaceutical and Biomedical Analysis. 2017;146:48-52.
doi:10.1016/j.jpba.2017.08.017 .

Stajić, Ana, Anđelković, Marija, Dikić, Nenad, Rasić, J., Vukašinović-Vesić, Milica, Ivanović, D., Jančić-Stojanović, Biljana, "Determination of higenamine in dietary supplements by UHPLC/MS/MS method" in Journal of Pharmaceutical and Biomedical Analysis, 146 (2017):48-52,
https://doi.org/10.1016/j.jpba.2017.08.017 . .

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  - Tumpa, Anja
AU  - Miladinović, Tamara
AU  - Rakić, Tijana
AU  - Stajić, Ana
AU  - Jančić-Stojanović, Biljana
PY  - 2016
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2567
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3444
AB  - A liquid chromatography method is reported for the determination of diclofenac potassium and its impurities using Quality by Design criteria. Central composite design was used for the investigation of the influence of critical parameters on performance that included the methanol concentration in the mobile phase, the pH of the aqueous phase, and the potassium dihydrogen phosphate concentration in the aqueous phase. Mathematical models enabled theoretical examination of experimental space to achieve maximal separation in minimal analysis time. A Monte Carlo simulation was used to evaluate the risk of uncertainty in model predictions, to adjusting process parameters, and to identify design space. Fractional factorial design was employed for robustness testing and method was fully validated. Optimal conditions were a C18 150mmx4.6mm, 5 mu m particle size column; a methanol -68.3mmolL(-1) potassium dihydrogenphosphate (68.7:31.3, v/v) mobile phase at pH 3.0, a flow rate of 1mL min(-1), a column temperature of 25 degrees C, and ultraviolet detection at 254nm.
PB  - Taylor & Francis Inc, Philadelphia
T2  - Analytical Letters
T1  - Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography
VL  - 49
IS  - 4
SP  - 445
EP  - 457
DO  - 10.1080/00032719.2015.1075131
ER  - 

@article{
author = "Tumpa, Anja and Miladinović, Tamara and Rakić, Tijana and Stajić, Ana and Jančić-Stojanović, Biljana",
year = "2016",
abstract = "A liquid chromatography method is reported for the determination of diclofenac potassium and its impurities using Quality by Design criteria. Central composite design was used for the investigation of the influence of critical parameters on performance that included the methanol concentration in the mobile phase, the pH of the aqueous phase, and the potassium dihydrogen phosphate concentration in the aqueous phase. Mathematical models enabled theoretical examination of experimental space to achieve maximal separation in minimal analysis time. A Monte Carlo simulation was used to evaluate the risk of uncertainty in model predictions, to adjusting process parameters, and to identify design space. Fractional factorial design was employed for robustness testing and method was fully validated. Optimal conditions were a C18 150mmx4.6mm, 5 mu m particle size column; a methanol -68.3mmolL(-1) potassium dihydrogenphosphate (68.7:31.3, v/v) mobile phase at pH 3.0, a flow rate of 1mL min(-1), a column temperature of 25 degrees C, and ultraviolet detection at 254nm.",
publisher = "Taylor & Francis Inc, Philadelphia",
journal = "Analytical Letters",
title = "Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography",
volume = "49",
number = "4",
pages = "445-457",
doi = "10.1080/00032719.2015.1075131"
}

Tumpa, A., Miladinović, T., Rakić, T., Stajić, A.,& Jančić-Stojanović, B.. (2016). Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography. in Analytical Letters
Taylor & Francis Inc, Philadelphia., 49(4), 445-457.
https://doi.org/10.1080/00032719.2015.1075131

Tumpa A, Miladinović T, Rakić T, Stajić A, Jančić-Stojanović B. Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography. in Analytical Letters. 2016;49(4):445-457.
doi:10.1080/00032719.2015.1075131 .

Tumpa, Anja, Miladinović, Tamara, Rakić, Tijana, Stajić, Ana, Jančić-Stojanović, Biljana, "Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography" in Analytical Letters, 49, no. 4 (2016):445-457,
https://doi.org/10.1080/00032719.2015.1075131 . .

TY  - JOUR
AU  - Maksić, Jelena
AU  - Tumpa, Anja
AU  - Popović, Igor
AU  - Jančić-Stojanović, Biljana
PY  - 2016
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2662
AB  - The purpose of the present research was to conduct stress degradation studies on the olopatadine hydrochloride, an antiallergic drug, using the hydrophilic interaction liquid chromatography (HILIC). HILIC requires the utilization of polar and moderately polar stationary phases and aqueous-organic mobile phase usually containing more than 70% of organic solvent. In this study, olopatadine hydrochloride was subjected to acid and base hydrolysis, oxidation and thermolytic degradation in order to estimate its stability under different stress conditions recommended by ICHQ1A (R2) guideline. Degree of degradation was followed by HILIC method. The chromatographic conditions were: column Betasil Cyano (100 mmx4.6 mm, 5 mu m particle size), mobile phase consisted of acetonitrile and ammonium acetate 5 mM (pH adjusted to 4.50) in ratio 85: 15 V/V, flow rate was 1 mL min(-1), column temperature was set at 30 degrees C and detection was performed at 257 nm. Results obtained for stress studies indicated that olopatadine hydrochloride underwent transformation under acidic and oxidative (30% hydrogen peroxyde) conditions showing high degree of degradation. Furthermore, it was found that olopatadine hydrochloride is relatively stable when exposed to thermal (60 degrees C) and basic (1 M NaOH) conditions. Therewith, kinetics of degradation reaction was determined with an aim to define the corresponding reaction rate constants and half-lives. Firstly, the order of the reaction was evaluated experimentally using the integral method. Based on the calculated values of the correlation coefficients, it was shown that the acidic, basic and oxidative degradation are the second-order reaction. High stability under basic conditions was achieved on the basis of the great degradation half-life values. Also, it has been verified that acidic degradation is the fastest reaction.
PB  - Savez hemijskih inženjera, Beograd
T2  - Hemijska industrija
T1  - Investigation of olopatadine hydrochloride under stress conditions by hydrophilic interaction liquid chromatography [Ispitivanje olopatadin-hidrohlorida pod stres uslovima metodom tečne hromatografije hidrofilnih interakcija]
VL  - 70
IS  - 3
SP  - 339
EP  - 346
DO  - 10.2298/HEMIND150404039M
ER  - 

@article{
author = "Maksić, Jelena and Tumpa, Anja and Popović, Igor and Jančić-Stojanović, Biljana",
year = "2016",
abstract = "The purpose of the present research was to conduct stress degradation studies on the olopatadine hydrochloride, an antiallergic drug, using the hydrophilic interaction liquid chromatography (HILIC). HILIC requires the utilization of polar and moderately polar stationary phases and aqueous-organic mobile phase usually containing more than 70% of organic solvent. In this study, olopatadine hydrochloride was subjected to acid and base hydrolysis, oxidation and thermolytic degradation in order to estimate its stability under different stress conditions recommended by ICHQ1A (R2) guideline. Degree of degradation was followed by HILIC method. The chromatographic conditions were: column Betasil Cyano (100 mmx4.6 mm, 5 mu m particle size), mobile phase consisted of acetonitrile and ammonium acetate 5 mM (pH adjusted to 4.50) in ratio 85: 15 V/V, flow rate was 1 mL min(-1), column temperature was set at 30 degrees C and detection was performed at 257 nm. Results obtained for stress studies indicated that olopatadine hydrochloride underwent transformation under acidic and oxidative (30% hydrogen peroxyde) conditions showing high degree of degradation. Furthermore, it was found that olopatadine hydrochloride is relatively stable when exposed to thermal (60 degrees C) and basic (1 M NaOH) conditions. Therewith, kinetics of degradation reaction was determined with an aim to define the corresponding reaction rate constants and half-lives. Firstly, the order of the reaction was evaluated experimentally using the integral method. Based on the calculated values of the correlation coefficients, it was shown that the acidic, basic and oxidative degradation are the second-order reaction. High stability under basic conditions was achieved on the basis of the great degradation half-life values. Also, it has been verified that acidic degradation is the fastest reaction.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "Hemijska industrija",
title = "Investigation of olopatadine hydrochloride under stress conditions by hydrophilic interaction liquid chromatography [Ispitivanje olopatadin-hidrohlorida pod stres uslovima metodom tečne hromatografije hidrofilnih interakcija]",
volume = "70",
number = "3",
pages = "339-346",
doi = "10.2298/HEMIND150404039M"
}

Maksić, J., Tumpa, A., Popović, I.,& Jančić-Stojanović, B.. (2016). Investigation of olopatadine hydrochloride under stress conditions by hydrophilic interaction liquid chromatography [Ispitivanje olopatadin-hidrohlorida pod stres uslovima metodom tečne hromatografije hidrofilnih interakcija]. in Hemijska industrija
Savez hemijskih inženjera, Beograd., 70(3), 339-346.
https://doi.org/10.2298/HEMIND150404039M

Maksić J, Tumpa A, Popović I, Jančić-Stojanović B. Investigation of olopatadine hydrochloride under stress conditions by hydrophilic interaction liquid chromatography [Ispitivanje olopatadin-hidrohlorida pod stres uslovima metodom tečne hromatografije hidrofilnih interakcija]. in Hemijska industrija. 2016;70(3):339-346.
doi:10.2298/HEMIND150404039M .

Maksić, Jelena, Tumpa, Anja, Popović, Igor, Jančić-Stojanović, Biljana, "Investigation of olopatadine hydrochloride under stress conditions by hydrophilic interaction liquid chromatography [Ispitivanje olopatadin-hidrohlorida pod stres uslovima metodom tečne hromatografije hidrofilnih interakcija]" in Hemijska industrija, 70, no. 3 (2016):339-346,
https://doi.org/10.2298/HEMIND150404039M . .

TY  - JOUR
AU  - Maksić, Jelena
AU  - Tumpa, Anja
AU  - Stajić, Ana
AU  - Jovanović, Marko
AU  - Rakić, Tijana
AU  - Jančić-Stojanović, Biljana
PY  - 2016
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2604
AB  - In this paper separation of granisetron and its two related substances in HILIC mode is presented. Separation was done on silica column derivatized with sulfoalkylbetaine groups (ZIC-HILIC). Firstly, retention mechanisms were assessed whereby retention factors of substances were followed in wide range of acetonitrile content (80-97%), at constant concentration of aqueous buffer (10 mM) as well as at constant pH value of 3.0. Further, in order to developed optimal HILIC method, Design of Experiments (DoE) methodology was applied. For optimization full factorial design 32 was employed. Influence of acetonitrile content and ammonium acetate concentration were investigated while pH of the water phase was kept at 3.3. Adequacy of obtained mathematical models was confirmed by ANOVA. Optimization goals (alpha > 1.15 and minimal run time) were accomplished with 94.7% of acetonitrile in mobile phase and 70 mM of ammonium acetate in water phase. Optimal point was in the middle of defined Design Space. In the next phase, robustness was experimetally tested by Rechtschaffen design. The investigated factors and their levels were: acetonitrile content (+/- 1%), ammonium acetate molarity in water phase (+/- 2 mM), pH value of water phase (+/- 0.2) and column temperature (+/- 4 degrees C). The validation scope included selectivity, linearity, accuracy and precision as well as determination of limit of detection (LOD) and limit of quantification (LOQ) for the related substances. Additionally, the validation acceptance criteria were met in all cases. Finally, the proposed method could be successfully utilized for estimation of granisetron HCl and its related substances in tablets and parenteral dosage forms, as well as for monitoring degradation under various stress conditions.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Hydrophilic interaction liquid chromatography in analysis of granisetron HCl and its related substances. Retention mechanisms and method development
VL  - 123
SP  - 93
EP  - 103
DO  - 10.1016/j.jpba.2016.02.010
ER  - 

@article{
author = "Maksić, Jelena and Tumpa, Anja and Stajić, Ana and Jovanović, Marko and Rakić, Tijana and Jančić-Stojanović, Biljana",
year = "2016",
abstract = "In this paper separation of granisetron and its two related substances in HILIC mode is presented. Separation was done on silica column derivatized with sulfoalkylbetaine groups (ZIC-HILIC). Firstly, retention mechanisms were assessed whereby retention factors of substances were followed in wide range of acetonitrile content (80-97%), at constant concentration of aqueous buffer (10 mM) as well as at constant pH value of 3.0. Further, in order to developed optimal HILIC method, Design of Experiments (DoE) methodology was applied. For optimization full factorial design 32 was employed. Influence of acetonitrile content and ammonium acetate concentration were investigated while pH of the water phase was kept at 3.3. Adequacy of obtained mathematical models was confirmed by ANOVA. Optimization goals (alpha > 1.15 and minimal run time) were accomplished with 94.7% of acetonitrile in mobile phase and 70 mM of ammonium acetate in water phase. Optimal point was in the middle of defined Design Space. In the next phase, robustness was experimetally tested by Rechtschaffen design. The investigated factors and their levels were: acetonitrile content (+/- 1%), ammonium acetate molarity in water phase (+/- 2 mM), pH value of water phase (+/- 0.2) and column temperature (+/- 4 degrees C). The validation scope included selectivity, linearity, accuracy and precision as well as determination of limit of detection (LOD) and limit of quantification (LOQ) for the related substances. Additionally, the validation acceptance criteria were met in all cases. Finally, the proposed method could be successfully utilized for estimation of granisetron HCl and its related substances in tablets and parenteral dosage forms, as well as for monitoring degradation under various stress conditions.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Hydrophilic interaction liquid chromatography in analysis of granisetron HCl and its related substances. Retention mechanisms and method development",
volume = "123",
pages = "93-103",
doi = "10.1016/j.jpba.2016.02.010"
}

Maksić, J., Tumpa, A., Stajić, A., Jovanović, M., Rakić, T.,& Jančić-Stojanović, B.. (2016). Hydrophilic interaction liquid chromatography in analysis of granisetron HCl and its related substances. Retention mechanisms and method development. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 123, 93-103.
https://doi.org/10.1016/j.jpba.2016.02.010

Maksić J, Tumpa A, Stajić A, Jovanović M, Rakić T, Jančić-Stojanović B. Hydrophilic interaction liquid chromatography in analysis of granisetron HCl and its related substances. Retention mechanisms and method development. in Journal of Pharmaceutical and Biomedical Analysis. 2016;123:93-103.
doi:10.1016/j.jpba.2016.02.010 .

Maksić, Jelena, Tumpa, Anja, Stajić, Ana, Jovanović, Marko, Rakić, Tijana, Jančić-Stojanović, Biljana, "Hydrophilic interaction liquid chromatography in analysis of granisetron HCl and its related substances. Retention mechanisms and method development" in Journal of Pharmaceutical and Biomedical Analysis, 123 (2016):93-103,
https://doi.org/10.1016/j.jpba.2016.02.010 . .

TY  - JOUR
AU  - Tumpa, Anja
AU  - Miladinović, Tamara
AU  - Rakić, Tijana
AU  - Stajić, Ana
AU  - Jančić-Stojanović, Biljana
PY  - 2016
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2567
AB  - A liquid chromatography method is reported for the determination of diclofenac potassium and its impurities using Quality by Design criteria. Central composite design was used for the investigation of the influence of critical parameters on performance that included the methanol concentration in the mobile phase, the pH of the aqueous phase, and the potassium dihydrogen phosphate concentration in the aqueous phase. Mathematical models enabled theoretical examination of experimental space to achieve maximal separation in minimal analysis time. A Monte Carlo simulation was used to evaluate the risk of uncertainty in model predictions, to adjusting process parameters, and to identify design space. Fractional factorial design was employed for robustness testing and method was fully validated. Optimal conditions were a C18 150mmx4.6mm, 5 mu m particle size column; a methanol -68.3mmolL(-1) potassium dihydrogenphosphate (68.7:31.3, v/v) mobile phase at pH 3.0, a flow rate of 1mL min(-1), a column temperature of 25 degrees C, and ultraviolet detection at 254nm.
PB  - Taylor & Francis Inc, Philadelphia
T2  - Analytical Letters
T1  - Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography
VL  - 49
IS  - 4
SP  - 445
EP  - 457
DO  - 10.1080/00032719.2015.1075131
ER  - 

@article{
author = "Tumpa, Anja and Miladinović, Tamara and Rakić, Tijana and Stajić, Ana and Jančić-Stojanović, Biljana",
year = "2016",
abstract = "A liquid chromatography method is reported for the determination of diclofenac potassium and its impurities using Quality by Design criteria. Central composite design was used for the investigation of the influence of critical parameters on performance that included the methanol concentration in the mobile phase, the pH of the aqueous phase, and the potassium dihydrogen phosphate concentration in the aqueous phase. Mathematical models enabled theoretical examination of experimental space to achieve maximal separation in minimal analysis time. A Monte Carlo simulation was used to evaluate the risk of uncertainty in model predictions, to adjusting process parameters, and to identify design space. Fractional factorial design was employed for robustness testing and method was fully validated. Optimal conditions were a C18 150mmx4.6mm, 5 mu m particle size column; a methanol -68.3mmolL(-1) potassium dihydrogenphosphate (68.7:31.3, v/v) mobile phase at pH 3.0, a flow rate of 1mL min(-1), a column temperature of 25 degrees C, and ultraviolet detection at 254nm.",
publisher = "Taylor & Francis Inc, Philadelphia",
journal = "Analytical Letters",
title = "Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography",
volume = "49",
number = "4",
pages = "445-457",
doi = "10.1080/00032719.2015.1075131"
}

Tumpa, A., Miladinović, T., Rakić, T., Stajić, A.,& Jančić-Stojanović, B.. (2016). Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography. in Analytical Letters
Taylor & Francis Inc, Philadelphia., 49(4), 445-457.
https://doi.org/10.1080/00032719.2015.1075131

Tumpa A, Miladinović T, Rakić T, Stajić A, Jančić-Stojanović B. Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography. in Analytical Letters. 2016;49(4):445-457.
doi:10.1080/00032719.2015.1075131 .

Tumpa, Anja, Miladinović, Tamara, Rakić, Tijana, Stajić, Ana, Jančić-Stojanović, Biljana, "Quality by Design Determination of Diclofenac Potassium and its Impurities by High-Performance Liquid Chromatography" in Analytical Letters, 49, no. 4 (2016):445-457,
https://doi.org/10.1080/00032719.2015.1075131 . .

TY  - JOUR
AU  - Terzić, Jelena
AU  - Popović, Igor
AU  - Stajić, Ana
AU  - Tumpa, Anja
AU  - Jančić-Stojanović, Biljana
PY  - 2016
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2548
AB  - This paper deals with the development of hydrophilic interaction liquid chromatographic (HILIC) method for the analysis of bilastine and its degradation impurities following Analytical Quality by Design approach. It is the first time that the method for bilastine and its impurities is proposed. The main objective was to identify the conditions where an adequate separation in minimal analysis duration could be achieved within a robust region. Critical process parameters which have the most influence on method performance were defined as acetonitrile content in the mobile phase, pH of the aqueous phase and ammonium acetate concentration in the aqueous phase. Box-Behnken design was applied for establishing a relationship between critical process parameters and critical quality attributes. The defined mathematical models and Monte Carlo simulations were used to identify the design space. Fractional factorial design was applied for experimental robustness testing and the method is validated to verify the adequacy of selected optimal conditions: the analytical column Luna (R) HILIC (100 mm x 4.6 mm, 5 mu m particle size); mobile phase consisted of acetonitrile aqueous phase (50 mM ammonium acetate, pH adjusted to 5.3 with glacial acetic acid) (90.5:9.5, v/v); column temperature 30 degrees C, mobile phase flow rate 1 mL min(-1), wavelength of detection 275 nm.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Pharmaceutical and Biomedical Analysis
T1  - Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method
VL  - 125
SP  - 385
EP  - 393
DO  - 10.1016/j.jpba.2016.04.022
ER  - 

@article{
author = "Terzić, Jelena and Popović, Igor and Stajić, Ana and Tumpa, Anja and Jančić-Stojanović, Biljana",
year = "2016",
abstract = "This paper deals with the development of hydrophilic interaction liquid chromatographic (HILIC) method for the analysis of bilastine and its degradation impurities following Analytical Quality by Design approach. It is the first time that the method for bilastine and its impurities is proposed. The main objective was to identify the conditions where an adequate separation in minimal analysis duration could be achieved within a robust region. Critical process parameters which have the most influence on method performance were defined as acetonitrile content in the mobile phase, pH of the aqueous phase and ammonium acetate concentration in the aqueous phase. Box-Behnken design was applied for establishing a relationship between critical process parameters and critical quality attributes. The defined mathematical models and Monte Carlo simulations were used to identify the design space. Fractional factorial design was applied for experimental robustness testing and the method is validated to verify the adequacy of selected optimal conditions: the analytical column Luna (R) HILIC (100 mm x 4.6 mm, 5 mu m particle size); mobile phase consisted of acetonitrile aqueous phase (50 mM ammonium acetate, pH adjusted to 5.3 with glacial acetic acid) (90.5:9.5, v/v); column temperature 30 degrees C, mobile phase flow rate 1 mL min(-1), wavelength of detection 275 nm.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Pharmaceutical and Biomedical Analysis",
title = "Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method",
volume = "125",
pages = "385-393",
doi = "10.1016/j.jpba.2016.04.022"
}

Terzić, J., Popović, I., Stajić, A., Tumpa, A.,& Jančić-Stojanović, B.. (2016). Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method. in Journal of Pharmaceutical and Biomedical Analysis
Elsevier Science BV, Amsterdam., 125, 385-393.
https://doi.org/10.1016/j.jpba.2016.04.022

Terzić J, Popović I, Stajić A, Tumpa A, Jančić-Stojanović B. Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method. in Journal of Pharmaceutical and Biomedical Analysis. 2016;125:385-393.
doi:10.1016/j.jpba.2016.04.022 .

Terzić, Jelena, Popović, Igor, Stajić, Ana, Tumpa, Anja, Jančić-Stojanović, Biljana, "Application of Analytical Quality by Design concept for bilastine and its degradation impurities determination by hydrophilic interaction liquid chromatographic method" in Journal of Pharmaceutical and Biomedical Analysis, 125 (2016):385-393,
https://doi.org/10.1016/j.jpba.2016.04.022 . .

TY  - JOUR
AU  - Jančić-Stojanović, Biljana
AU  - Vemić, Sava
AU  - Elezović, Valentina
AU  - Petrović, Ana
AU  - Sinadinović, Zoran
AU  - Ivanović, Darko
AU  - Damjanović, Svetozar S.
AU  - Miljković, Branislava
PY  - 2015
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2438
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/3432
AB  - A simple and reliable new HPLC method with UV detection has been developed and validated for simultaneous determination of mitotane and its two metabolites DDA and DDE. Method development was carried out utilizing systematical approach of the design of experiments (DoE) methodology. For estimation of factors influence on selected chromatographic responses and definition of the optimal chromatographic conditions, Box-Behnken experimental design was applied. The defined optimal separation conditions were: column Restek Ultra Aqua C-18 with pre-column Restek Ultra Aqua C-18 operating at temperature 35 degrees C; mixture of acetonitrile and 0.5% formic acid as mobile phase with 1.2mL min(-1) flow rate and detection at 230nm. As sample preparation method, liquid-liquid extraction was chosen. Method was fully validated and LOQ and LOD were experimentally determined. Finally, method was successfully applied for determination of mitotane and its metabolites in plasma samples of patients with adrenocortical carcinoma.
PB  - Taylor & Francis Inc, Philadelphia
T2  - Journal of Liquid Chromatography & Related Technologies
T1  - Development of New Liquid Chromatographic Method for Mitotane and Its Metabolites Determination in Human Plasma Employing Design of Experiments Methodology
VL  - 38
IS  - 14
SP  - 1371
EP  - 1378
DO  - 10.1080/10826076.2015.1057645
ER  - 

@article{
author = "Jančić-Stojanović, Biljana and Vemić, Sava and Elezović, Valentina and Petrović, Ana and Sinadinović, Zoran and Ivanović, Darko and Damjanović, Svetozar S. and Miljković, Branislava",
year = "2015",
abstract = "A simple and reliable new HPLC method with UV detection has been developed and validated for simultaneous determination of mitotane and its two metabolites DDA and DDE. Method development was carried out utilizing systematical approach of the design of experiments (DoE) methodology. For estimation of factors influence on selected chromatographic responses and definition of the optimal chromatographic conditions, Box-Behnken experimental design was applied. The defined optimal separation conditions were: column Restek Ultra Aqua C-18 with pre-column Restek Ultra Aqua C-18 operating at temperature 35 degrees C; mixture of acetonitrile and 0.5% formic acid as mobile phase with 1.2mL min(-1) flow rate and detection at 230nm. As sample preparation method, liquid-liquid extraction was chosen. Method was fully validated and LOQ and LOD were experimentally determined. Finally, method was successfully applied for determination of mitotane and its metabolites in plasma samples of patients with adrenocortical carcinoma.",
publisher = "Taylor & Francis Inc, Philadelphia",
journal = "Journal of Liquid Chromatography & Related Technologies",
title = "Development of New Liquid Chromatographic Method for Mitotane and Its Metabolites Determination in Human Plasma Employing Design of Experiments Methodology",
volume = "38",
number = "14",
pages = "1371-1378",
doi = "10.1080/10826076.2015.1057645"
}

Jančić-Stojanović, B., Vemić, S., Elezović, V., Petrović, A., Sinadinović, Z., Ivanović, D., Damjanović, S. S.,& Miljković, B.. (2015). Development of New Liquid Chromatographic Method for Mitotane and Its Metabolites Determination in Human Plasma Employing Design of Experiments Methodology. in Journal of Liquid Chromatography & Related Technologies
Taylor & Francis Inc, Philadelphia., 38(14), 1371-1378.
https://doi.org/10.1080/10826076.2015.1057645

Jančić-Stojanović B, Vemić S, Elezović V, Petrović A, Sinadinović Z, Ivanović D, Damjanović SS, Miljković B. Development of New Liquid Chromatographic Method for Mitotane and Its Metabolites Determination in Human Plasma Employing Design of Experiments Methodology. in Journal of Liquid Chromatography & Related Technologies. 2015;38(14):1371-1378.
doi:10.1080/10826076.2015.1057645 .

Jančić-Stojanović, Biljana, Vemić, Sava, Elezović, Valentina, Petrović, Ana, Sinadinović, Zoran, Ivanović, Darko, Damjanović, Svetozar S., Miljković, Branislava, "Development of New Liquid Chromatographic Method for Mitotane and Its Metabolites Determination in Human Plasma Employing Design of Experiments Methodology" in Journal of Liquid Chromatography & Related Technologies, 38, no. 14 (2015):1371-1378,
https://doi.org/10.1080/10826076.2015.1057645 . .

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  - Colović, Jelena
AU  - Kalinić, Marko
AU  - Vemić, Ana
AU  - Erić, Slavica
AU  - Malenović, Anđelija
PY  - 2015
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/2365
AB  - The aim of this study was to systematically investigate the phenomena affecting the retention behavior of structurally diverse basic drugs in ion-interaction chromatographic systems with chaotropic additives. To this end, the influence of three factors was studied: pH value of the aqueous phase, concentration of sodium hexafluorophosphate, and content of acetonitrile in the mobile phase. Mobile phase pH was found to affect the thermodynamic equilibria in the studied system beyond its effects on the analytes' ionization state. Specifically, increasing pH from 2 to 4 led to longer retention times, even with analytes which remain completely protonated. An explanation for this phenomenon was sought by studying the adsorption behavior of acetonitrile and chaotropic additive onto stationary phase. It was shown that the magnitude of the developed surface potential, which significantly affects retention - increases with pH, and that this can be attributed to the larger surface excess of acetonitrile. To study how analytes' structural properties influence their retention, quantitative structure-retention modeling was performed next. A support vector machine regression model was developed, relating mobile phase constituents and structural descriptors with retention data. While the ETA_EtaP_B_RC and XlogP can be considered as molecular descriptors which describe factors affecting retention in any RP-HPLC system, TDB9p and RDF45p are molecular descriptors which account for spatial arrangement of polarizable atoms and they can clearly relate to analytes' behavior on the stationary phase surface, where the electrostatic potential develops. Complementarity of analytes' structure with that of the electric double layer can be seen as a key factor influencing their retention behavior. Structural diversity of analytes and good predictive capabilities over a range of experimental conditions make the established model a useful tool in predicting retention behavior in the studied chromatographic system.
PB  - Elsevier Science BV, Amsterdam
T2  - Journal of Chromatography A
T1  - Investigation into the phenomena affecting the retention behavior of basic analytes in chaotropic chromatography: Joint effects of the most relevant chromatographic factors and analytes' molecular properties
VL  - 1425
SP  - 150
EP  - 157
DO  - 10.1016/j.chroma.2015.11.027
ER  - 

@article{
author = "Colović, Jelena and Kalinić, Marko and Vemić, Ana and Erić, Slavica and Malenović, Anđelija",
year = "2015",
abstract = "The aim of this study was to systematically investigate the phenomena affecting the retention behavior of structurally diverse basic drugs in ion-interaction chromatographic systems with chaotropic additives. To this end, the influence of three factors was studied: pH value of the aqueous phase, concentration of sodium hexafluorophosphate, and content of acetonitrile in the mobile phase. Mobile phase pH was found to affect the thermodynamic equilibria in the studied system beyond its effects on the analytes' ionization state. Specifically, increasing pH from 2 to 4 led to longer retention times, even with analytes which remain completely protonated. An explanation for this phenomenon was sought by studying the adsorption behavior of acetonitrile and chaotropic additive onto stationary phase. It was shown that the magnitude of the developed surface potential, which significantly affects retention - increases with pH, and that this can be attributed to the larger surface excess of acetonitrile. To study how analytes' structural properties influence their retention, quantitative structure-retention modeling was performed next. A support vector machine regression model was developed, relating mobile phase constituents and structural descriptors with retention data. While the ETA_EtaP_B_RC and XlogP can be considered as molecular descriptors which describe factors affecting retention in any RP-HPLC system, TDB9p and RDF45p are molecular descriptors which account for spatial arrangement of polarizable atoms and they can clearly relate to analytes' behavior on the stationary phase surface, where the electrostatic potential develops. Complementarity of analytes' structure with that of the electric double layer can be seen as a key factor influencing their retention behavior. Structural diversity of analytes and good predictive capabilities over a range of experimental conditions make the established model a useful tool in predicting retention behavior in the studied chromatographic system.",
publisher = "Elsevier Science BV, Amsterdam",
journal = "Journal of Chromatography A",
title = "Investigation into the phenomena affecting the retention behavior of basic analytes in chaotropic chromatography: Joint effects of the most relevant chromatographic factors and analytes' molecular properties",
volume = "1425",
pages = "150-157",
doi = "10.1016/j.chroma.2015.11.027"
}

Colović, J., Kalinić, M., Vemić, A., Erić, S.,& Malenović, A.. (2015). Investigation into the phenomena affecting the retention behavior of basic analytes in chaotropic chromatography: Joint effects of the most relevant chromatographic factors and analytes' molecular properties. in Journal of Chromatography A
Elsevier Science BV, Amsterdam., 1425, 150-157.
https://doi.org/10.1016/j.chroma.2015.11.027

Colović J, Kalinić M, Vemić A, Erić S, Malenović A. Investigation into the phenomena affecting the retention behavior of basic analytes in chaotropic chromatography: Joint effects of the most relevant chromatographic factors and analytes' molecular properties. in Journal of Chromatography A. 2015;1425:150-157.
doi:10.1016/j.chroma.2015.11.027 .

Colović, Jelena, Kalinić, Marko, Vemić, Ana, Erić, Slavica, Malenović, Anđelija, "Investigation into the phenomena affecting the retention behavior of basic analytes in chaotropic chromatography: Joint effects of the most relevant chromatographic factors and analytes' molecular properties" in Journal of Chromatography A, 1425 (2015):150-157,
https://doi.org/10.1016/j.chroma.2015.11.027 . .