Investigation of experimental approaches to the determination of pKa values by capillary electrophoresis

Determination of dissociation constants of folic acid, methotrexate, and other photolabile pteridines by pressure-assisted capillary electrophoresis

“…Buffer viscosity and hydration properties vary upon composition and pH changes, introducing systematic error in the recorded m eff values [21]. Cleveland et al [21] proposed to coinject a permanently charged marker with the sample as internal mobility reference. In the absence of protolytic equilibria, any change in m eff marker exceeding the instrumental error is a measure of the "buffer discontinuity" effect.…”

“…The pK and m L 2 parameters of this function are obtained by nonlinear regression, which is preferred over linearization approaches [21].…”

“…CZE was introduced as a tool for characterization of acid-base chemistry in 1991 [19]. Since then, over 60 papers have been published in this field [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and the developments have recently been reviewed [25]. The determination of ionization constants by CE relies on registration of effective electrophoretic mobility (m eff ) in a series of BGE solutions with varying pH and constant ionic strength (I = Sz 2 i c i for all ions).…”

Capillary electrophoresis for the analysis of small‐molecule pharmaceuticals

“…Technetium radiopharmaceuticals pH range 1.3-6.6 50 mbar PACE Citric acid adjusted with NaOH [200] Anthrocyclines (antibiotics) pH 4.20-8.20 [202] Cytokinins (phytohormones) pH 1.5-6.0 [203] Dihydrofolate reductase inhibitors pH 2.1-4.5 50 mM phosphate buffer adjusted with phosphoric acid/NaOH [204] Quinolones (antibacterials) pH 2.0-11.0 [205] Ropinirole and impurities (Parkinson's treatment) pH 2.20-11.42 [206] pK a of organic bases in aqueous methanol (0-70% v/v) pH range 4.76-9.5 Tris, ethanolamine and acetate buffers [207] pK a of N-imidazole derivative aromatase inhibitors pH range 3.88-9.16 25 mM phosphate buffer adjusted with triethylamine [208] pH values [185][186][187][188][189][190][191][192][193][194][195][196][197]. Table 7 details a selection of reported applications.…”

Determination of dissociation constants of amino acids by capillary zone electrophoresis

“…An automated method for obtaining the pK a values of acids and bases using CE was described and is suitable for determining the pK a value of compound with low water solubility [20]. Several approaches for the calculation of the pK a value from CE data were proposed by Gluck and Cleveland [21]. Nonlinear regression was the simplest and most precise regression procedure for determining the pK a value of a solute by CE.…”