DETERMINATION OF METFORMIN IN PLASMA BY CAPILLARY ELECTROPHORESIS USING FIELD-AMPLIFIED SAMPLE STACKING TECHNIQUE

A capillary electrophoresis method was described for the determination of metformin in human plasma based on the extraction of the ion-pair with bromothymol blue into chloroform. Phenformin was used as internal standard. Field-amplified sample stacking injection was employed with an electrokinetic injection voltage of 10 kV for 10 s. The running bu ffer was 0.1 M phosphate buffer (pH 2.5), running voltage was 20 kV an d the UV absorbance detection was set at 195 nm. The limit of quantita tion was 0.25 mu g/ml. Linearity range of calibration curve was 0.25 t o 3.5 mu g/ml. Recoveries for three levels (0.25, 1 and 2 mu g/ml) wer e 80.24%, 67.44% and 58.97% (n=5 for each level), respectively. The in tra-day precisions for the three levels were 11.9%, 3.09% and 4.33% an d the inter-day precisions were 12.4%, 4.57% and 4.94%, respectively. The concentrations of metformin hydrochloride in human plasma of eight volunteers were measured after orally administrating metformin enteri c-capsule and tablet. (C) 1998 Elsevier Science B.V.