Column-switching high-performance liquid chromatographic (HPLC) determination of hydrochlorothiazide in rat, dog, and human plasma

A fully automated HPLC assay for hydrochlorothiazide in plasma has been developed using a column-switching technique. The method involves direct injection of plasma to the extraction column for sample cleanup followed by switching onto the analytical column. Good precision, accuracy, and linearity were obtained over a range of 25 to 2000 ng/ml in rat, dog, and human plasma. The column-switching method has also been validated by comparison with a conventional HPLC method requiring a cumbersome plasma extraction procedure. Since the method is simple, rapid, and reproducible, it is useful for determination of hydrochlorothiazide levels in animal and human plasma.