DETERMINATION OF DISSOCIATION-CONSTANTS OF CEPHALOSPORINS BY CAPILLARY-ZONE-ELECTROPHORESIS

Although the cephalosporins are important drugs in medical and in phar maceutical research, the pK(a) of these substances is frequently not k nown. Dissociation constants of cephalosporins were determined by capi llary zone electrophoresis (CZE) as a new technique and potentiometric titration (PMT) at low solute concentrations. The CZE method relies o n measuring the ionic mobility of the solute as a function of pH. Mobi lity and pH data are fitted to an equilibrium expression by using nonl inear regression. The total analysis time for the determination of the pK(a) using CZE was 40 min. Potentiometric titration was performed as a comparative method to CZE for the determination of the dissociation constants. The total analysis time was 50 min and the sample concentr ation was between 200 and 300 mu g/ml. (C) 1998 Elsevier Science.