SOLID-PHASE EXTRACTION TECHNIQUES FOR ASSAY OF DIURETICS IN HUMAN URINE SAMPLES

Solid-phase extraction techniques were evaluated for the treatment of urine samples in the analysis of diuretics before injection into an HP-Hypersyl ODS-C18 column. Six different reversed-phase extraction columns were tested, and the results obtained are compared with those obtained in a classical liquid-liquid extraction with ethyl acetate. The solid-phase extraction procedures are the best overall choice for all the diuretics tested, due to their versatility, the minor time-consuming, and the good recovery percentages obtained. C18 and C-8 packings give the highest recoveries for a majority of the diuretics studied. However, CH or PH columns, due to their greater selectivity, can be used if the elution of the matrix is not complete in the washing solution. This could be more suitable to obtain satisfactory recoveries of the more polar diuretics such as acetazolamide or hydrochlorothiazide.