A single-run HPLC–PDA method for simultaneous screening of sibutramine, phenolphthalein, caffeine and furosemide in weight-loss products

Abstract

Background: A high-performance liquid chromatography method with photodiode-array detection (HPLC-PDA) was developed and validated for the simultaneous quantification of caffeine (CAF), furosemide (FUR), phenolphthalein (PHE), and sibutramine (SIB) in herbal weight-loss products. Materials and Methods: The method employed methanol for sample extraction and utilized a C18 column with a phosphate buffer-acetonitrile gradient. Results: Validation according to ICH and AOAC guidelines confirmed excellent linearity (10-150 µg mL⁻¹, R² ≥ 0.991), accuracy (spike recovery: 95.89-103.08 %), and precision (intra- and inter-day RSD ≤ 2.66 %). The limits of detection and quantification were sufficiently low to detect these adulterants at trace levels. Application to 32 commercial products from Vietnam revealed that 28.1 % (9 samples) were adulterated with four synthetic drugs, primarily with SIB alone or in combination with PHE. Conclusion: These findings underscore the need for enhanced regulatory oversight of the weight-loss supplement market. Thus, this method represents a robust, sustainable, and readily applicable solution for quality control laboratories.