Evaluation of boron-doped diamond electrode for simultaneous voltammetric determination of hydrochlorothiazide and losartan in pharmaceutical formulations

A method for the simultaneous determination of hydrochlorothiazide (HCTZ) and losartan (LOS) in pharmaceutical formulations using differential-pulse voltammetry (DPV) was developed. Two very well-resolved and reproducible oxidation peaks of HCTZ and LOS, with separation of 0.23 V, were obtained in Britton-Robinson (BR) buffer (pH 9.5) using an anodically pretreated boron-doped diamond electrode. Under the optimum analytical experimental conditions, the voltammetric method exhibited linear responses for simultaneous determination of HCTZ and LOS in the concentration range 3.0 × 10−6 to 7.4 × 10−5 mol L−1 for both compounds, with detection limits of 1.2 × 10−6 mol L−1 and 9.5 × 10−7 mol L−1, respectively. The proposed method was successfully applied in the simultaneous determination of LOS and HCTZ content in pharmaceutical formulations, whose accuracy was attested by good agreement of the results (paired t-test at a 95% confidence level) with those obtained using high performance liquid chromatography (HPLC).