Spectrophotometric determination of ionization constants by capillary zone electrophoresis

Semi-empirical relationships between effective mobility, charge, and molecular weight of pharmaceuticals by pressure-assisted capillary electrophoresis: Applications in drug discovery

“…Determination of maximum Z c values and appropriate model equation of multiprotic pharmaceuticals with close pK a values using Eqs. (5) and (6) Compound MW (g/mol)…”

“…(5) and (6) Model to Z c /MW x relationships were utilized for CE method development to predict the m eff of five dibases at different pH values and choose an appropriate pH to achieve optimal separation. Additionally, the equations were used to determine the potential valency of and apply the appropriate model equation to seven multiprotic acids and bases with closely spaced pK a values.…”

“…For these reasons, the CE methodology has proven extremely useful in the analysis of a wide range of molecules including peptides, proteins, and pharmaceuticals. In the past decade, a number of methods utilizing CE for determination of negative log of the dissociation constant (pK a ) have been reported [1][2][3][4][5][6][7][8][9][10][11]. Since 1998, CE has been employed to determine the pK a s of many different types of molecules including amino acids, pharmaceuticals, metabolites, and radiopharmaceuticals [12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

Estimation of pKa values using microchip capillary electrophoresis and indirect fluorescence detection

“…UV detection is perhaps the most popular [10][11][12][13][14][15][16][17][18][19][20] of the CE-based approaches for the estimation of pK a values, although conductometric [18], amperometric [21], and indirect UV detection [22] have also been used. In an important study, Barbosa et al.…”

Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

“…(13) predicts a sigmoidal behaviour of A s versus pH. This expression can be applied for the spectroscopic determination of dissociation constants in aqueous media, pK a, by CZE experiments [14] or apparent dissociation constants in micellar media, pKa,app, by MEKC experiments, provided that the molar absorptivities ella and e a differ sufficiently at the applied wavelength. Notice that for micellar media K~ should be replaced by K,~.,pr.…”