Development and validation of eco-friendly micellar HPLC method for the simultaneous determination of hydrochlorothiazide and valsartan in bulk powder and pharmaceutical dosage forms

Ongoing greener in chromatography, new methodologies have to be developed using safer mobile phase composition and/or lower solvent consumption. The new methods should also consider the applicability in industrial facilities where selection criteria are based mainly on profit through cost and time. The drugs under study, valsartan (VAL) and hydrochlorothiazide (HCT), are co-formulated as tablet dosage form which is considered a widely consumed first-line treatment for hypertension. The use of the biodegradable non-ionic surfactant Brij-35 (0.1 M) in the aqueous phase increased the surface polarity of the bonded C18 stationary phase by its polyoxyethylene chain. This change gave faster separation of the analytes in short analysis time, enabled the use of methanol instead of acetonitrile which is more environmentally safe and also decreased its ratio required to enhance elution to only 25%. Fast isocratic separation was achieved at flow 1 mL min−1 where the retention times were 2.9 and 4.3 min for VAL and HCT, respectively, using UV detection at 254 nm. The method was validated according to ICH guidelines. High accuracy results were obtained at linearity range of 5–100 µg mL−1 for both drugs. LOD and LOQ were (1.01 and 3.05 µg mL−1) for VAL and (1.01 and 3.09 µg mL−1) for HCT, respectively. The method was successfully applied for determination of the drugs in their marketed dosage form. Since claiming greenness is not enough, the proposed method was compared favorably with published methods using the new assessment tool, GAPI index.