IMPROVED ELECTROCHEMICAL DETECTION OF DIURETICS IN HIGHPERFORMANCE LIQUID-CHROMATOGRAPHIC ANALYSIS BY POSTCOLUMN ONLINE PHOTOLYSIS

A sensitive, high-performance liquid chromatographic method including postcolumn on-line UV irradiation and electrochemical detection is des cribed for the determination of pharmaceuticals with diuretic action. The investigations on this liquid chromatography-photolysis-coulometri c detection approach indicate that, depending on the substituents of t he compounds, oxidation of drugs containing an aromatic chloride and t hiazide moiety occurs at potentials as low as +200 mV. Parameters infl uencing the electrochemical response are given to optimize the reactio n conditions. The procedure presented allows the quantification of diu retics, and consequently of chemically related substances, with good r eproducibility and high selectivity at the picogram level.