EVALUATION OF AMPEROMETRIC DETECTION AT A GLASSY-CARBON ELECTRODE FOR THE LIQUID-CHROMATOGRAPHIC DETERMINATION OF ANTIHYPERTENSIVE SUBSTANCES

A liquid chromatographic technique with amperometric detection has been developed for determining the antihypertensive drugs captopril, todralazine and prazosin in human serum samples. The technique is based on the oxidation possibilities of these compounds at glassy carbon electrodes. An individual electrochemical study of the three compounds has been carried out and the solution and instrumental variables, such as joint oxidation potential, pH, and buffer and mobile-phase compositions, have been optimized. The internal standard selected was timolol, a beta-blocker drug with antihypertensive effects that has similar groups, that can be oxidized at a glassy carbon electrode. Conditions for the prior extraction of the three substances from serum have been established using solid-liquid extraction cartridges. The technique proposed permits the simultaneous determination of trace amounts of captopril, todralazine and prazosin in human serum samples, with detection limits of 0.20, 0.004 and 0.06 mu g ml(-1), respectively, and recoveries of 95.8, 99.8 and 98.7%.