An Improved HPLC Method for Simultaneous Analysis of Losartan Potassium and Hydrochlorothiazide with the Aid of a Chemometric Protocol

An experimental design method was used for fast, simple, and accurate high-performance-pressure liquid chromatograpy (HPLC) determination of losartan and hydrochlorothiazide in combined dosage forms. This method avoids the disadvantages of the traditional analytical approach, which is time-consuming, involves a large number of runs, and does not allow the determination of multiple interacting parameters. On the basis of preliminary experiments, three independent variables (methanol content, pH value of the mobile phase, and flow rate) were selected as input, and as dependent variables, five responses (retention time of hydrochlorothiazide, retention time of losartan, asymmetry of hydrochlorothiazide peak, asymmetry of losartan peak, and resolution) were chosen. A full 2³ factorial design was used to determine which factors had an effect on the studied response. Afterwards, experimental design was used to optimize these influencing parameters in the previously selected experimental domain. After optimizing the experimental conditions, a separation was conducted on a Zorbax C₈ (150 mm × 4.6 mm, 5 μm particle size) column with a mobile phase consisting of methanol–acetonitrile–acetate buffer 45:20:35 v/v/v, pH 4.8 with flow rate of 0.82 mL min^?1 and column temperature of 25 °C. The developed method was successfully applied to simultaneous separation of these active drug compounds in their commercial pharmaceutical dosage forms.