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 described for the determination of pharmaceuticals with diuretic action. The investigations on this liquid chromatography-photolysis-coulometric detection approach indicate that, depending on the substituents of the compounds, oxidation of drugs containing an aromatic chloride and thiazide moiety occurs at potentials as low as +200 mV. Parameters influencing the electrochemical response are given to optimize the reaction conditions. The procedure presented allows the quantification of diuretics, and consequently of chemically related substances, with good reproducibility and high selectivity at the picogram level.