Simultaneous determination of sibutramine and its derivatives in weight loss dietary supplements by LC-MS/MS

Abstract

The liquid chromatography tandem mass spectrometry method (LC-MS/MS) was used to determine the content of sibutramine (SB), N-desmethyl sibutramine (DSB) and N-didesmethyl sibutramine (DDSB) illegaly mixed in weight loss dietary supplements. Sibutramine and its derivatives were extracted by methanol; impurities in the extract were removed by graphitized carbon black (GCB) adsorbent. The chromatographic separation of analytes took place on C18 column (100 mm x 2.1 mm, 3.5 µm) with a gradient mobile phase of acetonitrile and 2 mM ammonium acetate in 0.1% formic acid solution. Multiple reaction monitoring (MRM) in the positive mode was used to detect and quantify SB, DSB and DDSB at m/z 279.9/124.8; 266.0/124.8 and 252.1/125.0, respectively. The method was validated following the AOAC requirements for specificity, repeatability and recovery. Calibration curves lineared from 0.002 to 0.1 µg/mL for SB, DSB and DDSB. The method was successfully applied to determine the content of SB, DSB and DDSB in weight loss dietary supplements that were randomly collected from phamacies in Hanoi of three formulations of hard capsule, soft capsule and teabag. The results shown that six samples had SB and DSB with the content in the range of 0.817 - 31.7 mg/g.