LIQUID CHROMATOGRAPHIC DETERMINATION OF CHLOROTHIAZIDE AND HYDROCHLOROTHIAZIDE DIURETIC DRUGS IN BOVINE-MILK

A liquid chromatographic (LC) procedure was developed for the determin ation of chlorothiazide (CTZ) and hydrochlorothiazide (HCTZ) in bovine milk. Whole milk was defatted by centrifugation at 4 degrees C. The t op layer was treated with lead acetate and acetonitrile, mixed, and ce ntrifuged. The supernatant was extracted with ethyl acetate to remove acetonitrile. The solvent mixture was further treated with sodium tung state and mixed. The top layer was removed and evaporated to dryness, the residue was dissolved in the mobile phase, and the final extract w as analyzed by LC. The LC employed a polymer column, a mobile phase of acetonitrile/tetrahydrofuran in phosphate buffer, and a UV detector. The average recoveries of CTZ from milk fortified at 35, 70, and 140 p pb were 97, 96, and 99%, respectively, with corresponding coefficients of variation (CVs) of 8, 5, and 5%. The average recoveries of HCTZ at 35, 70, and 140 ppb were 87, 91, and 90%, respectively, with CVs of 5 , 6, and 5%. The method was validated by assaying milk obtained from c ows dosed separately with the two diuretics. CTZ was detected in 8-h ( 430 ppb) and 24-h (85 ppb) incurred milk samples and HCTZ (47 ppb) onl y in the 8-h incurred milk samples.