title: Internal standard capillary electrophoresis as a high-throughput method for pKa determination in drug discovery and development.
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.
authors.affiliation: Departament de Química Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona , Martí i Franquès 1-11, E-08028 Barcelona, Spain.
authors.forename: Joan M
authors.initials: JM
authors.lastname: Cabot
authors.forename: Elisabet
authors.initials: E
authors.lastname: Fuguet
authors.forename: Martí
authors.initials: M
authors.lastname: Rosés
mesh_terms: D002021:Buffers; D055808:Drug Discovery / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D057166:High-Throughput Screening Assays / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D012015:Reference Standards; D015203:Reproducibility of Results; D013816:Thermodynamics
chemical_list: D002021:Buffers
keywords: IS-CE; acidity constant; capillary electrophoresis; high-throughput method; internal standard; pKa determination