Simultaneous Determination of Valsartan and Chlorthalidone in Human Plasma by Using Liquid Chromatography-Tandem Mass Spectrometry

A sensitive and reliable LC-MS/MS method was established and validated for the simultaneous quantification of valsartan (VAL) and chlorthalidone (CHL) in human plasma. Sample preparation involved a liquid-liquid extraction approach. Chromatographic separations of the analytes and their isotopically labeled internal standards, valsartan-d9 (VALD9) and chlorthalidone-d4 (CHLD4), were achieved using a Waters XBridge C18 column (100 × 4.6 mm, 3.5 µm). Detection was carried out via electrospray ionization in negative mode, employing multiple reaction monitoring (MRM). The ion transitions monitored were m/z 434.2 → 179.1 for VAL and m/z 337.1 → 146.05 for CHL. Calibration curves exhibited good linearity over concentration ranges of 25 - 20,000 ng/mL for valsartan and 2 - 1000 ng/mL for chlorthalidone. The validated method demonstrates suitability for use in bioequivalence assessments involving human plasma samples.