Application of ultra-high-performance liquid chromatography coupled with LTQ-Orbitrap mass spectrometry for identification, confirmation and quantitation of illegal adulterated weight-loss drugs in plant dietary supplements

In this paper, an ultra-high-performance liquid chromatography coupled with linear ion trap quadrupole Orbitrap high resolution mass spectrometry (UHPLC-LTQ-Orbitrap HRMS) method was developed and validated for identification, confirmation and quantitation of illegal adulterated weight-loss drugs in plant dietary supplements. 13 wt-loss drugs were well separated by the gradient elution of 10 mmol/L ammonium acetate − 0.05% formic acid H2O and acetonitrile at a flow rate of 0.2 mL/min within 12 min. The MS analysis was operated under the positive ion and in full MS/dd-MS2 (data-dependent MS2) mode. The full MS scan with resolution at 60 000 FWHM and narrow mass windows at 5 ppm acquired data for identification and quantitation, and dd-MS2 scan with resolution at 15 000 FWHM obtained product ions for confirmation. The method validation showed good linearity with coefficients of determination (r2) higher than 0.9951 for all analytes. Meantime, all the LOD and LLOQ values were in the respective range of 0.3-2 and 1-9 ng/g. The accuracy, intra- and inter-day precision were in the ranges of −1.7 to 3.4%, 1.7-5.0% and 1.9-4.4%, respectively. The mean recoveries ranged from 85.4 to 107.1%, while the absolute and relative matrix effect were in the corresponding range of 98.2-108.6% and 2.6-8.7%. Among 120 batches of weight loss plant dietary supplements, sibutramine and fluoxertine or both were positive in 29 samples. In general, LTQ-Orbitrap HRMS technology was a powerful tool for the analysis of illegal ingredients in dietary supplements.