Determination of cilazapril and hydrochlorothiazide in pharmaceuticals by high performance liquid chromatography

A high performance liquid chromatography method was developed for the specific determination of cilazapril (CZP), hydrochlorothiazide (HCT) binary mixtures in pharmaceutical dosage form. Active substances were seperated by gradient system in that mobile phase consists of methanol-phosphate buffer. As a mobile phase flow rate was 0.8 ml.min(-1) and Lichrospher 100 RP-18e (5 mum, 250 x 4 mm) was used as a stationary phase. Detection was carried out using a UV detector at 254 nm and trimethoprim (TM) as an internal standard. The detector response was linear in the range of 15-200 mug.mL(-1) for CZP and 10-150 mug.mL(-1) for HCT. The relative standard deviation for this method was determined to be 1.35 and 1.67% for CZP and HCT respectively.