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Hajduk A, Ulrich N. Determination of acidity constants of pyridines, imidazoles, and oximes by capillary electrophoresis. Electrophoresis 2023; 44:1353-1360. [PMID: 37377077 DOI: 10.1002/elps.202300037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 06/11/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023]
Abstract
The acidity constant in the form of pKa is one of the most important physicochemical quantities. There are prediction tools available for calculating the pKa , but they only deliver precise calculated values for a relatively small set of chemicals. For complex structures with multiple functional groups in particular, the error in the predicted pKa is high due to the application domain of the corresponding models. Thus, we aim to enlarge the dataset of experimentally determined pKa values using capillary electrophoresis. We, therefore, selected various pyridines, imidazoles, and oximes to determine the pKa values using the internal standard approach and the classical method. Especially oximes were not investigated in the past, and predictions for them include larger errors. Thus, our experimentally determined values could contribute to an improved understanding of various functional groups impacting the pKa values and serve as additional datasets to develop improved pKa prediction tools.
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Affiliation(s)
- Anna Hajduk
- Department of Ecological Chemistry, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Nadin Ulrich
- Department of Ecological Chemistry, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
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2
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Nowak PM, Biel I, Kózka G, Klag M, Woźniakiewicz M. Influence of pH measurement inaccuracy on the values of acidity constant determined on the basis of electrophoretic and thermophoretic data. Microchem J 2022. [DOI: 10.1016/j.microc.2022.107689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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3
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Dinç E, Ertekin ZC. Two Different Strategies Based on Three‐Way Analysis Models of UV Spectroscopic and Spectrochromatographic Measurements to Quantify the Acidity Constant of Acetylsalicylic Acid. ChemistrySelect 2022. [DOI: 10.1002/slct.202104345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Erdal Dinç
- Department of Analytical Chemistry Ankara University Faculty of Pharmacy 06560 Yenimahalle Ankara Turkey
| | - Zehra Ceren Ertekin
- Department of Analytical Chemistry Ankara University Faculty of Pharmacy 06560 Yenimahalle Ankara Turkey
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4
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Nytrová L, Odehnalová K, Pazourek J. Extension of the Internal Standard Method for Determination of Thermodynamic Acidity Constants of Compounds Sparingly Soluble in Water by Capillary Zone Electrophoresis. ACS OMEGA 2022; 7:1477-1482. [PMID: 35036810 PMCID: PMC8756569 DOI: 10.1021/acsomega.1c06224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 12/17/2021] [Indexed: 06/14/2023]
Abstract
The paper extends applicability of the internal standard method published in 2009 (Fuguet E. et al., J. Chromatogr. A 2009, 1216(17), 3646). Although the original capillary zone electrophoresis method was suggested to determine thermodynamic acidity constants of compounds sparingly soluble in aqueous solutions by carrying out only runs at two different pH values (i.e., without the need to perform many experiments over the appropriate pH range including the form of a low-ionized analyte), we proved that the approach also virtually overcomes any interactions of the analyte in mixed solvents, so that the experiments can be carried out in a methanol-water buffer where the solubility is much better. Applicability of the extended method is illustrated on six selected β-blockers.
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Affiliation(s)
- Lucie Nytrová
- Department
of Chemical Drugs, Faculty of Pharmacy, Masaryk University, Palackého 1946/1, CZ-612 00 Brno, Czech Republic
| | - Klára Odehnalová
- Department
of Chemical Drugs, Faculty of Pharmacy, Masaryk University, Palackého 1946/1, CZ-612 00 Brno, Czech Republic
- Department
of Experimental Phycology and Ecotoxicology, Institute of Botany of the Czech Academy of Sciences, Research Division Brno, Lidická
25/27, CZ-602 00 Brno, Czech Republic
| | - Jiří Pazourek
- Department
of Chemical Drugs, Faculty of Pharmacy, Masaryk University, Palackého 1946/1, CZ-612 00 Brno, Czech Republic
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5
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Albishri A, Cabot JM, Fuguet E, Rosés M. Determination of the aqueous pK a of very insoluble drugs by capillary electrophoresis: Internal standards for methanol-water extrapolation. J Chromatogr A 2021; 1665:462795. [PMID: 35042141 DOI: 10.1016/j.chroma.2021.462795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 12/28/2021] [Accepted: 12/29/2021] [Indexed: 10/19/2022]
Abstract
A fast determination of acidity constants (pKa) of very insoluble drugs has become a necessity in drug discovery process because it often produces molecules that are highly lipophilic and sparingly soluble in water. In this work the high throughput internal standard capillary electrophoresis (IS-CE) method has been adapted to the determination of pKa of water insoluble compounds by measurement in methanol/aqueous buffer mixtures. For this purpose, the reference pKa values for a set of 46 acid-base compounds of varied structure (internal standards) have been established in methanol-water mixtures at several solvent composition levels (with a maximum of 40% methanol). The IS-CE method has been successfully applied to seven test drugs of different chemical nature with intrinsic solubilities lower than 10-6 M. pKa values have been determined at different methanol/aqueous buffer compositions and afterwards Yasuda-Shedlovsky extrapolation method has been applied to obtain the aqueous pKa. The obtained results have successfully been compared to literature ones obtained by other methods. It is concluded that the IS-CE method allows the determination of aqueous pKa values using low proportions of methanol, becoming then more accurate in the extrapolation procedure than other reference methods.
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Affiliation(s)
- Abdulkarim Albishri
- Departament de Química Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí i Franquès 1-11 E, Barcelona 08028, Spain
| | - Joan M Cabot
- Leitat Technology Center, Innovació 2, Barcelona 08225, Spain.
| | - Elisabet Fuguet
- Departament de Química Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí i Franquès 1-11 E, Barcelona 08028, Spain; Serra Húnter Programm, Generalitat de Catalunya, Barcelona, Spain
| | - Martí Rosés
- Departament de Química Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí i Franquès 1-11 E, Barcelona 08028, Spain.
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6
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Nowak PM, Mitoraj M, Sagan F, Wietecha-Posłuszny R. Differentiation of isomeric metabolites of carbamazepine based on acid-base properties; Experimental vs theoretical approach. J Chromatogr A 2021; 1651:462275. [PMID: 34090055 DOI: 10.1016/j.chroma.2021.462275] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 05/14/2021] [Accepted: 05/18/2021] [Indexed: 01/01/2023]
Abstract
Metabolism of carbamazepine is complex and leads to the three isomeric derivatives whose occurrence is dependent on the type of sample material. Their unambiguous differentiation is overall important. In this work, the qualitative analysis of 2-hydroxycarbamazepine, 3-hydroxycrbamazepine and carbamazepine-10,11-epoxide was attempted for the first time using capillary zone electrophoresis, based on the models linking electrophoretic mobility with pKa value determining the acidity of the hydroxyl groups. For this purpose, pKa values were determined using electrophoretic and theoretical methods, and then the compliance of the obtained mobility models with the measured values was analyzed. Despite the slight difference in acidity (0.3-0.4 pH unit), the obtained results prove that the correct identification of the metabolites under consideration, and reliable prediction of the selectivity of their separation, are possible on the basis of experimentally determined pKa values, even with highly simplified methods assuming the lack of certain data. However, it is important to choose the optimal pH value, which should be close to pKa. On the other hand, worse results were obtained for the theoretically determined mobilities, which differed significantly from the experimental values. An attempt was also made to explain the acidity of hydroxycarbamazepines and the associated thermodynamic parameters - deprotonation enthalpy and entropy, with respect to their structure. The lack of intramolecular hydrogen bonds and the significant contribution of entropic effects stabilizing the protonated form seems to be significant. The higher pKa value for CBZ-2-OH probably results from the stronger effect of the energetically unfavorable organization of solvent dipoles due to ionization.
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Affiliation(s)
- Paweł Mateusz Nowak
- Jagiellonian University in Kraków, Faculty of Chemistry, Department of Analytical Chemistry, Gronostajowa St. 2, 30-387 Kraków, Poland.
| | - Mariusz Mitoraj
- Jagiellonian University in Kraków, Faculty of Chemistry, Department of Theoretical Chemistry, Gronostajowa St. 2, 30-387 Kraków, Poland
| | - Filip Sagan
- Jagiellonian University in Kraków, Faculty of Chemistry, Department of Theoretical Chemistry, Gronostajowa St. 2, 30-387 Kraków, Poland
| | - Renata Wietecha-Posłuszny
- Jagiellonian University in Kraków, Faculty of Chemistry, Department of Analytical Chemistry, Gronostajowa St. 2, 30-387 Kraków, Poland
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7
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Lebanov L, Fuguet E, Melo JM, Rosés M. Determination of acidity constants at 37 °C through the internal standard capillary electrophoresis (IS-CE) method: internal standards and application to polyprotic drugs. Analyst 2020; 145:5897-5904. [PMID: 32671360 DOI: 10.1039/d0an00918k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This work provides the pKa at the biorelevant temperature of 37 °C for a set of compounds proposed as internal standards for the internal standard capillary electrophoresis (IS-CE) method. This is a high throughput method that allows the determination of the acidity constants of compounds in a short time, avoiding the exact measurement of the pH of the buffers used. pH electrode calibration at 37 °C can be avoided too. In order to anchor the pKa values obtained through the IS-CE method in the pH scale, the acidity constant at 37 °C of some of the standards has been determined also by the reference potentiometric method. In general, a decrease in the pKa value is observed when changing the temperature from 25 to 37 °C, and the magnitude of the change depends on the nature of the compounds. Once the pKa values at 37 °C of the internal standards have been established, the method is applied to the determination of the acidity constants of seven polyprotic (5 diprotic and 2 triprotic) drugs. The obtained mobility-pH profiles show well-defined curves, and the fits provide precise pKa values. Due to the lack of reference data at 37 °C only the pKa values of labetalol can be compared to values from the literature, and a very good agreement is observed.
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Affiliation(s)
- Leo Lebanov
- Departament d'Enginyeria Química i Química Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí I Franquès 1-11, 08028, Barcelona, Spain.
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8
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Quality by Design-Based Development of a Chiral Capillary Electrophoresis Method for the Determination of Dextrodropropizine and 1-Phenylpiperazine as Impurities of Levodropropizine. Chromatographia 2019. [DOI: 10.1007/s10337-019-03817-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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9
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Dardonville C. Automated techniques in pK a determination: Low, medium and high-throughput screening methods. DRUG DISCOVERY TODAY. TECHNOLOGIES 2018; 27:49-58. [PMID: 30103863 DOI: 10.1016/j.ddtec.2018.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 04/03/2018] [Accepted: 04/05/2018] [Indexed: 06/08/2023]
Abstract
Drug discovery programs that generate hundreds of new molecular entities need efficient methodologies for physicochemical profiling. Several high-throughput methods for pKa screening have been developed in the last 15 years to determine this key physicochemical parameter. Separation techniques such as HPLC-MS or capillary electrophoresis are particularly well-suited due to their high throughput and capacity to deal with impure or complex samples. In addition, potentiometric and (mostly) UV-metric-based methods (plate-based and automated systems), find their place as very precise methodologies for pKa determination despite of somewhat lower throughput. Finally, pKa prediction software packages are useful estimator tools but, to date, they cannot replace experimental measurements when accurate pKa values are required.
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10
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Woźniakiewicz M, Nowak PM, Gołąb M, Adamowicz P, Kała M, Kościelniak P. Acidity of substituted cathinones studied by capillary electrophoresis using the standard and fast alternative approaches. Talanta 2018; 180:193-198. [DOI: 10.1016/j.talanta.2017.12.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 12/08/2017] [Accepted: 12/11/2017] [Indexed: 11/26/2022]
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11
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Thermodynamics of acid-base dissociation of several cathinones and 1‐phenylethylamine, studied by an accurate capillary electrophoresis method free from the Joule heating impact. J Chromatogr A 2018; 1539:78-86. [DOI: 10.1016/j.chroma.2018.01.047] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 01/17/2018] [Accepted: 01/21/2018] [Indexed: 12/12/2022]
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12
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Nowak PM, Woźniakiewicz M, Piwowarska M, Kościelniak P. Determination of acid dissociation constant of 20 coumarin derivatives by capillary electrophoresis using the amine capillary and two different methodologies. J Chromatogr A 2016; 1446:149-57. [DOI: 10.1016/j.chroma.2016.03.084] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 03/24/2016] [Accepted: 03/30/2016] [Indexed: 11/30/2022]
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13
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Liu C, Yamaguchi Y, Sekine S, Ni Y, Li Z, Zhu X, Dou X. Gene analysis of multiple oral bacteria by the polymerase chain reaction coupled with capillary polymer electrophoresis. J Sep Sci 2015; 39:986-92. [PMID: 26648455 DOI: 10.1002/jssc.201501087] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 11/09/2015] [Accepted: 11/30/2015] [Indexed: 12/16/2022]
Abstract
Capillary polymer electrophoresis is identified as a promising technology for the analysis of DNA from bacteria, virus and cell samples. In this paper, we propose an innovative capillary polymer electrophoresis protocol for the quantification of polymerase chain reaction products. The internal standard method was modified and applied to capillary polymer electrophoresis. The precision of our modified internal standard protocol was evaluated by measuring the relative standard deviation of intermediate capillary polymer electrophoresis experiments. Results showed that the relative standard deviation was reduced from 12.4-15.1 to 0.6-2.3%. Linear regression tests were also implemented to validate our protocol. The modified internal standard method showed good linearity and robust properties. Finally, the ease of our method was illustrated by analyzing a real clinical oral sample using a one-run capillary polymer electrophoresis experiment.
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Affiliation(s)
- Chenchen Liu
- Engineering Research Center of Optical Instrument and System, University of Shanghai for Science and Technology, Shanghai, China.,Institute of Photonics and Bio-medicine (IPBM), Graduate School of Science, East China University of Science and Technology (ECUST), Shanghai, China
| | - Yoshinori Yamaguchi
- Institute of Photonics and Bio-medicine (IPBM), Graduate School of Science, East China University of Science and Technology (ECUST), Shanghai, China.,Department of Applied Physics, Graduate School of Engineering, Osaka University, Osaka, Japan
| | - Shinichi Sekine
- Division of Special Care Dentistry, Osaka University Dental Hospital, Osaka University, Osaka, Japan.,Department of Preventive Dentistry, Osaka University Graduate School of Dentistry Osaka University, Osaka, Japan
| | - Yi Ni
- Institute of Photonics and Bio-medicine (IPBM), Graduate School of Science, East China University of Science and Technology (ECUST), Shanghai, China
| | - Zhenqing Li
- Engineering Research Center of Optical Instrument and System, University of Shanghai for Science and Technology, Shanghai, China
| | - Xifang Zhu
- School of Optoelectronic Engineering, ChangZhou Institute of Technology, Changzhou, Jiangsu, China
| | - Xiaoming Dou
- Institute of Photonics and Bio-medicine (IPBM), Graduate School of Science, East China University of Science and Technology (ECUST), Shanghai, China.,School of Optoelectronic Engineering, ChangZhou Institute of Technology, Changzhou, Jiangsu, China
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14
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Determination of acid dissociation constants of warfarin and hydroxywarfarins by capillary electrophoresis. J Pharm Biomed Anal 2015; 112:89-97. [DOI: 10.1016/j.jpba.2015.04.027] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 04/17/2015] [Accepted: 04/18/2015] [Indexed: 01/18/2023]
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15
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Zrnčić M, Babić S, Mutavdžić Pavlović D. Determination of thermodynamic pKavalues of pharmaceuticals from five different groups using capillary electrophoresis. J Sep Sci 2015; 38:1232-9. [DOI: 10.1002/jssc.201401057] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 01/13/2015] [Accepted: 01/13/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Mirta Zrnčić
- Department of Analytical Chemistry; Faculty of Chemical Engineering and Technology; University of Zagreb; Zagreb Croatia
| | - Sandra Babić
- Department of Analytical Chemistry; Faculty of Chemical Engineering and Technology; University of Zagreb; Zagreb Croatia
| | - Dragana Mutavdžić Pavlović
- Department of Analytical Chemistry; Faculty of Chemical Engineering and Technology; University of Zagreb; Zagreb Croatia
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16
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Saygılı R, Ulus R, Yeşildağ İ, Kübra İnal E, Kaya M, Murat Kalfa O, Zeybek B. Synthesis of some 1,8-dioxoacridine carboxylic acid derivatives and the determination of their ionization constants in ethanol–water mixtures. J Mol Struct 2015. [DOI: 10.1016/j.molstruc.2014.12.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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17
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Nowak P, Woźniakiewicz M, Kościelniak P. Application of capillary electrophoresis in determination of acid dissociation constant values. J Chromatogr A 2014; 1377:1-12. [PMID: 25543298 DOI: 10.1016/j.chroma.2014.12.032] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 12/05/2014] [Accepted: 12/09/2014] [Indexed: 11/20/2022]
Abstract
The chemical groups undergoing protonation or deprotonation in solution are described by the acid dissociation constant value, the key parameter for physicochemical characterization of biologically- and pharmacologically-important compounds. Capillary electrophoresis (CE) proved to be suitable technique for its determination: it enables automated and accurate measurements even for minute amount of sample, does not require the information about concentration, and handle both the impure and complex samples. In this review, a number of contributions reporting on the application of CE in pKa prediction has been summarized and critically discussed. The reader will find herein the brief introduction of theory, summary of all works published in the last decade, considerations on the most important innovations and achievements, and the discussion of pKa-related issues as e.g. the role of pKa-shifts in the chiral separation mechanism or the elucidation of migration order reversals observed during CE-mediated separations.
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Affiliation(s)
- Paweł Nowak
- Jagiellonian University in Kraków, Faculty of Chemistry, Department of Analytical Chemistry, Kraków, Poland
| | - Michał Woźniakiewicz
- Jagiellonian University in Kraków, Faculty of Chemistry, Department of Analytical Chemistry, Kraków, Poland.
| | - Paweł Kościelniak
- Jagiellonian University in Kraków, Faculty of Chemistry, Department of Analytical Chemistry, Kraków, Poland
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18
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Cabot JM, Fuguet E, Rosés M. Determination of acidity constants of sparingly soluble drugs in aqueous solution by the internal standard capillary electrophoresis method. Electrophoresis 2014; 35:3564-9. [DOI: 10.1002/elps.201400353] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 09/01/2014] [Accepted: 09/01/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Joan Marc Cabot
- Departament de Química Analítica and Institut de Biomedicina de la Universitat de Barcelona; Universitat de Barcelona; Barcelona Spain
| | - Elisabet Fuguet
- Departament de Química Analítica and Institut de Biomedicina de la Universitat de Barcelona; Universitat de Barcelona; Barcelona Spain
| | - Martí Rosés
- Departament de Química Analítica and Institut de Biomedicina de la Universitat de Barcelona; Universitat de Barcelona; Barcelona Spain
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19
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Partition coefficients of organic compounds between water and imidazolium-, pyridinium-, and phosphonium-based ionic liquids. Anal Bioanal Chem 2014; 406:8021-31. [DOI: 10.1007/s00216-014-8264-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 10/03/2014] [Accepted: 10/08/2014] [Indexed: 11/25/2022]
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20
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Cabot JM, Fuguet E, Rosés M. Internal standard capillary electrophoresis as a high-throughput method for pKa determination in drug discovery and development. ACS COMBINATORIAL SCIENCE 2014; 16:518-25. [PMID: 25170674 DOI: 10.1021/co500059p] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel high-throughput method for determining acidity constants (pKa) by capillary electrophoresis (CE) is developed. The method, based on the use of an internal standard (IS-CE), is implemented as a routine method for accurate experimental pKa determination of drugs undergoing physicochemical measurements in drug discovery laboratories. Just two electropherograms at 2 different pH values are needed to calculate an acidity constant. Several ISs can be used in the same buffer and run to enhance precision. With 3 ISs, for example, the pKa of the test compound (TC) can be obtained in triplicate in less than 3 min of electrophoresis. It has been demonstrated that the IS-CE method eliminates some systematic errors, maintaining, or even increasing the precision of the results compared with other methods. Furthermore, pH buffer instability during electrophoretic runs is not a problem in the IS-CE method. It is also proved that after 16 h of electroseparation using the same buffer vial, pH may change by around one unit; but the pKa calculated by the IS-CE method remains constant. Thus, IS-CE is a powerful high-throughput method for pKa determination in drug discovery and development.
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Affiliation(s)
- Joan M. Cabot
- Departament de Química
Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain
| | - Elisabet Fuguet
- Departament de Química
Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain
| | - Martí Rosés
- Departament de Química
Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain
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21
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Deeb SE, Wätzig H, El-Hady DA, Albishri HM, de Griend CSV, Scriba GKE. Recent advances in capillary electrophoretic migration techniques for pharmaceutical analysis. Electrophoresis 2014; 35:170-89. [PMID: 24395663 DOI: 10.1002/elps.201300411] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 10/04/2013] [Accepted: 10/04/2013] [Indexed: 12/31/2022]
Abstract
Since the introduction about 30 years ago, CE techniques have gained a significant impact in pharmaceutical analysis. The present review covers recent advances and applications of CE for the analysis of pharmaceuticals. Both small molecules and biomolecules such as proteins are considered. The applications range from the determination of drug-related substances to the analysis of counterions and the determination of physicochemical parameters. Furthermore, general considerations of CE methods in pharmaceutical analysis are described.
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Affiliation(s)
- Sami El Deeb
- Drug Analysis and Research Center, Department of Pharmaceutical Chemistry, Al-Azhar University - Gaza, Gaza, Palestine; Institute of Medicinal and Pharmaceutical Chemistry, TU Braunschweig, Braunschweig, Germany
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22
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TAKAYANAGI T, INOUE G, IKUTA A. Analysis of Binding Equilibrium of Phenylalkylamines to Brij 58 Micelle through the Measurement of Electrophoretic Mobility by CZE. CHROMATOGRAPHY 2014. [DOI: 10.15583/jpchrom.2014.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Toshio TAKAYANAGI
- Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University
| | - Genki INOUE
- Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University
| | - Ayumi IKUTA
- Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University
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23
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Wang JL, Xu XJ, Chen DY. Determination of pKa values of a triptolide derivative and its impurities by pressure-assisted capillary electrophoresis. J Pharm Biomed Anal 2014; 88:22-6. [DOI: 10.1016/j.jpba.2013.08.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 08/06/2013] [Accepted: 08/08/2013] [Indexed: 11/25/2022]
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24
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Šolínová V, Kašička V. Determination of acidity constants and ionic mobilities of polyprotic peptide hormones by CZE. Electrophoresis 2013; 34:2655-65. [PMID: 23775856 DOI: 10.1002/elps.201300119] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 04/23/2013] [Accepted: 04/23/2013] [Indexed: 12/16/2022]
Abstract
CZE has been applied to determination of thermodynamic acidity constants (pKa ) of ionogenic groups and actual ionic mobilities of polyprotic peptides-synthetic human and salmon gonadotropin-releasing hormones and their derivatives and fragments. First, the mixed acidity constants, pKa,imix, of ionogenic groups, and actual ionic mobilities, mi , of gonadotropin-releasing hormone peptides were determined by nonlinear regression analysis of pH dependence of their effective electrophoretic mobilities. The effective mobilities were measured by CZE in a series of BGEs within a broad pH range (1.80-12.10), at constant ionic strength (25 mM) and reference temperature (25°C). Second, the pKa,imix values were recalculated to thermodynamic pKa s using the Debye-Hückel theory. Thermodynamic pKa of carboxyl groups was estimated to be in the range of 2.5-3.3 for C-terminal amino acids of the above peptides, and 5.2 for glutamic acid in the middle of peptide chain; pKa of imidazolyl group of histidine residues was in the range of 5.7-6.8, pKa of N-terminal amino group of the peptide with free N-terminus was equal to 6.2, pKa of phenol group of tyrosine residues was in the range of 9.8-10.8, and pKa of guanidinyl group or arginine residues reached values 11.1-11.3, depending on the position of the residues in the peptide and on the amino acid sequence of the peptide. Absolute values of actual ionic mobilities of peptides with charge number ±2 were in the range (14.6-18.6) × 10(-9) m(2) V(-1) s(-1) , and ionic mobilities of peptides with charge number ±1 reached values (6.5-12.9) × 10(-9) m(2) V(-1) s(-1) .
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Affiliation(s)
- Veronika Šolínová
- Institute of Organic Chemistry and Biochemistry, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Reijenga J, van Hoof A, van Loon A, Teunissen B. Development of Methods for the Determination of pKa Values. ANALYTICAL CHEMISTRY INSIGHTS 2013; 8:53-71. [PMID: 23997574 PMCID: PMC3747999 DOI: 10.4137/aci.s12304] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The acid dissociation constant (pKa) is among the most frequently used physicochemical parameters, and its determination is of interest to a wide range of research fields. We present a brief introduction on the conceptual development of pKa as a physical parameter and its relationship to the concept of the pH of a solution. This is followed by a general summary of the historical development and current state of the techniques of pKa determination and an attempt to develop insight into future developments. Fourteen methods of determining the acid dissociation constant are placed in context and are critically evaluated to make a fair comparison and to determine their applications in modern chemistry. Additionally, we have studied these techniques in light of present trends in science and technology and attempt to determine how these trends might affect future developments in the field.
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Affiliation(s)
- Jetse Reijenga
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Arno van Hoof
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Antonie van Loon
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Bram Teunissen
- Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands
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Gravador RS, Fuguet E, Ràfols C, Rosés M. Temperature variation effects on the determination of acidity constants through the internal standard-capillary electrophoresis method. Electrophoresis 2013; 34:1203-11. [DOI: 10.1002/elps.201200584] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 11/30/2012] [Accepted: 12/05/2012] [Indexed: 11/07/2022]
Affiliation(s)
- Rufielyn S. Gravador
- Departament de Química Analítica and Institut de Biomedicina de la Universitat de Barcelona; Universitat de Barcelona; Barcelona; Spain
| | - Elisabet Fuguet
- Departament de Química Analítica and Institut de Biomedicina de la Universitat de Barcelona; Universitat de Barcelona; Barcelona; Spain
| | - Clara Ràfols
- Departament de Química Analítica and Institut de Biomedicina de la Universitat de Barcelona; Universitat de Barcelona; Barcelona; Spain
| | - Martí Rosés
- Departament de Química Analítica and Institut de Biomedicina de la Universitat de Barcelona; Universitat de Barcelona; Barcelona; Spain
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Cabot JM, Fuguet E, Ràfols C, Rosés M. Determination of acidity constants by the capillary electrophoresis internal standard method. IV. Polyprotic compounds. J Chromatogr A 2013; 1279:108-16. [DOI: 10.1016/j.chroma.2013.01.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 12/21/2012] [Accepted: 01/03/2013] [Indexed: 11/27/2022]
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Martínez CHR, Dardonville C. Rapid Determination of Ionization Constants (pK a) by UV Spectroscopy Using 96-Well Microtiter Plates. ACS Med Chem Lett 2013; 4:142-5. [PMID: 24900577 DOI: 10.1021/ml300326v] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 11/20/2012] [Indexed: 11/28/2022] Open
Abstract
We have developed a methodology that enables for the rapid measurement of ionization constants (pK a) of series of compounds by UV spectrophotometry. This protocol, which is straightforward to set up, takes advantage of the sensitivity of UV spectroscopy and the throughput enabled by the 96-well microplate (as opposed to the use of 1 cm quartz cuvette). The compounds, in stock solutions in DMSO, are dissolved in several aqueous buffer solutions directly in the microtiter plate, allowing the simultaneous determination of the UV spectra as a function of pH. Further treatment of the data provides the pK a values in a medium-throughput manner. The pK a values of 11 new antitrypanosomal dibasic compounds were determined using this methodology.
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