[Determination of sodium phenytoin in plasma by high performance capillary zone electrophoresis]

A method to determine sodium phenytoin in plasma by high performance capillary zone electrophoresis (CZE) has been established. CZE was performed in 25 mmol/L phosphate buffer solution (pH 12) at 20 degrees C. The capillary column size was 75 microns i.d. x 30 cm (effective length). Sodium phenytoin was quantified with UV detector at 200 nm. The plasma was extracted by ether after plasma was processed with proteinase K for 3 h at 55 degrees C. Then the extract was evaporated to dryness. The residue was reconstituted in 1 mL of running buffer. The average recovery was higher than 95%. The precisions of intra-day and inter-day were 3.1% and 4.7% respectively. The detection limit of sodium phenytoin was 0.6 mg/L.