Determination of hydrochlorothiazide in serum by high-pressure liquid chromatography

A quantitative high-pressure liquid chromatographic method has been developed for the analysis of hydrochlorothiazide in serum in therapeutical concentrations. The method is based on gel filtration of the sera on Sephadex G-15, extraction of the protein-free fraction of the effluent with ethyl acetate and injection of a methanol solution of the drug extract on a reversed-phase column packed with Spherisorb ODS (particle size, 10 mum). The mobile phase is 15% methanol in water. The detection limit is 50 ng/ml of serum. Serum samples from patients receiving hydrochlorothiazide have been analysed by the described method at different hours postdose.