Comparative determination of sibutramine as an adulterant in natural slimming products by HPLC and HPTLC densitometry

A new validated method for the identification and quantification of the sibutramine was developed by HPTLC-densitometry at 225 nm and advantages and disadvantages compared with HPLC-FLD at 225 nm emission and 316 nm excitation. Both methods were applied to the analysis of three natural slimming products in the market for the quantitative analysis of illegally added sibutramine. HPTLC separations were performed on (20 cm × 10 cm) glass HPTLC plates coated with silica gel 60 F254 using a mobile phase, n-hexane–acetone–ammonia (10:1:0.1, v/v/v). For HPLC analysis, a phenyl column (5.0 μm, 150 mm × 4.6 mm, i.d.) and an isocratic mobile phase of acetonitrile–water–formic acid (pH 3.0; 0.19 M) (45:55:0.78, v/v/v) was used. The calibration curve area versus concentration was found to be linear in the range of 250–2000 ng/spot−1 and 5–200 μg/ml for HPTLC and HPLC, respectively. Both methods were validated for accuracy, precision, linearity, selectivity, recovery and short term stability. As a conclusion, these methods were found to be useful for the routine analysis of illegally added sibutramine in the marketed products.