Determination of the unbound clozapine concentration in human serum albumin (HSA), human plasma, rabbit serum and plasma samples by capillary electrophoresis in the frontal analysis mode (CE/FA) was developed.The unbound clozapine concentration was directly measured from the height of the frontal peak and the obtained results were compared with those of the conventional ultrafiltration method.Effects of separation voltage and composition of running buffer on the plateau were investigated and the optimized separation condition was determined.The protein binding selectivity of clozapine was discussed.

Key words: clozapine, HPCE/FA(high performance capillary electrophoresis-frontal analysis), protein binding, serum and plasma