A NEW RAPID AND ECONOMICAL HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ASSAY WITH ELECTROCHEMICAL DETECTION FOR THE DETERMINATION OF ETOPOSIDE (VP-16) IN HUMAN PLASMA SAMPLES

A high performance liquid chromatographic assay with electrochemical d etection has been developed for the determination of etoposide in huma n plasma samples. 2-acetamidophenol was used as internal standard and extraction was performed with ethyl ether-dichloromethane (2:1) in a s ingle step. Analyses were carried out on a Nova Pak C-8 column using m ethanol-75 mM acetate buffer (45:55) as mobile phase. The effluent fro m the column was monitorized at +800 mV against Ag/AgCl and the result ing current was registered. The assay was linear within the range of 0 .02-4 mu g/mL, coefficients of variation being lower than 10%. Detecti on limit was 5 ng/mL. The method is rapid and economical. Therefore, i t is suitable for routine monitoring of etoposide pharmacokinetics aft er administration of low oral doses according to recent therapeutic sc hemes.