Simultaneous analysis of candesartan cilexetil and hydrochlorothiazide in human plasma and dosage forms using HPLC with a photodiode array detector

A simple and fast HPLC method using a photodiode array detector was developed for the antihypertensive drugs, candesartan cilexetil, and hydrochlorothiazide in human plasma and dosage forms. The system requires a Supelcocil C-18 (5 mum, 15 cm X 4.6 mm) column, and a mobile phase composed of 10 mM potassium dihydrogen phosphate : methanol : acetonitrile (2 : 80 : 18, v/v/v) (pH 2.5) while at a flow rate 1.0 mL min(-1). Candesartan cilexetil and hydrochlorothiazide were detected at 260.0 nm and were eluted in 3.5 and 6.5 min, respectively, after injection. No endogenous substances were found to interfere. The method utilises protein precipitation with acetonitrile as the only sample preparation involved prior to reversed phase-HPLC. No internal standard was required. The linearity range for candesartan cilexetil and hydrochlorothiazide was 30.0-2500.0 ng mL(-1) and 20.0-1000.0 ng mL(-1), respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were estimated to be 2.0 and 11.0 ng mL(-1) for candesartan cilexetil and 3.58 and 6.75 ng mL(-1) for hydrochlorothiazide, respectively. The proposed method, which is rapid, simple, and does not require any separation step, has been successfully applied to the assay of dosage forms and human plasma containing candesartan cilexetil and hydrochlorothiazide.