Eco-friendly HPTLC method using central composite design for evaluation of hydrochlorothiazide and methyldopa simultaneously in tablet dosage form

Methyldopa and hydrochlorothiazide are used in tablet dosage form as antihypertensive agents. A developed high-performance thin-layer chromatographic method is easy to use, accurate, precise, and dependable for the simultaneous estimation of hydrochlorothiazide and methyldopa. An experimental design was employed for the multivariate optimization of the high-performance thin-layer chromatographic method’s experimental conditions. By using the central composite design, the factors’ influence on responses was carefully examined. In a total of 19 experimental trials, 5 centre points were framed with three factors, viz., variation in the mobile phase’s toluene volume (mL), the solvent’s travel distance (mm), and the saturation time (min). Chromatographic conditions were optimised by the utilisation of central composite design. Predicted and actual values observed in contour plots were provided the optimum chromatographic condition (mobile phase (toluene: methanol: formic acid (95%) 7:3:0.2, v/v/v), a solvent front of 75 mm, and a saturation time of 30 min) for estimation of these two drugs. Under these optimum conditions, the two drugs were separated with a proper baseline and showed sufficient resolution and good RF values. The validated test parameters were optimised in accordance with International Council of Harmonisation (ICH) guidelines. Eco-friendly green chemistry methods, like Analytical Greenness (AGREE) and Green Analytical Procedure Index (GAPI), were used to evaluate the environmental impact of the new high-performance thin-layer chromatographic method. The results showed that the Quality by Design (Central Composite Design) method may be effectively used to optimise the high-performance thin-layer chromatographic method for the simultaneous quantification of methyldopa and hydrochlorothiazide.