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 H 2 O 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-MS 2 (data-dependent MS 2 ) 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-MS 2 scan with resolution at 15 000 FWHM obtained product ions for confirmation. The method validation showed good linearity with coefficients of determination (r 2 ) 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.