Development and validation of HPLC-PDA method for simultaneous determination of sibutramine, furosemide, and phenolphthalein in solid form weight loss products

The illegal adulteration of weight loss products using pharmaceutical substances such as sibutramine, furosemide, and phenolphthalein poses a serious threat to public health. This study aimed to develop and validate a method for the simultaneous quantification of these compounds in weight loss dietary supplements using high-performance liquid chromatography with photodiode array detection (HPLC-PDA). The optimized method employed an InertSUSTAIN Phenyl column (250 mm × 4.6 mm, 5 µm), with a mobile phase of acetonitrile and 0.5% phosphoric acid (45% : 55%), a flow rate of 1 mL/min, and detection at 225 nm. Samples were extracted using 96% ethanol with a simple preparation procedure. The method was validated according to AOAC guidelines, including selectivity, linearity, accuracy, precision, limits of detection (LOD), limits of quantification (LOQ), and dilution integrity. The method showed excellent linearity (R² > 0.998), acceptable recoveries (95–103%), and low LODs and LOQs (0.161–0.758 µg/mL). Application of the method to 19 commercial weight loss products revealed 4 samples containing sibutramine and 2 samples containing phenolphthalein. This method is suitable for routine use in food control laboratories to ensure the safety of weight loss products.