Simultaneous Determination of Slimming Drugs in Dietary Supplements by Liquid Chromatography/Time-of-Flight Mass Spectrometry

Abstract

A method for the simultaneous determination of 13 slimming drugs in dietary supplements by liquid chromatography/time-of-flight mass spectrometry was developed and applied to real-time surveys of imported health supplements. The target compounds were mutually well separated on a reversed-phase LC Shodex ODP2-HP 2D column using a combination of step-wise and linear gradient elution of a mixed mobile phase solution of ammonium formate buffer, methanol, and formic acid. The detection limits were in the range 1-50 ng/mL, and the lower limits of quantification were 2-100 ng/mL. The average recoveries of the 13 types of pharmaceutical ingredients in the diet supplements were 93-110%, and the RSD was within 7.1%. Applying the developed method to the survey of imported dietary supplements revealed that 32 out of the 39 Chinese products tested contained pharmaceutical ingredients such as sibutramine. On the other hand, out of 30 US products, synephrine was detected in 26 specimens, and yohimbine was detected in 8 specimens. These results proved that a number of products were contaminated by drugs, which was considered to be intentional. The developed method is applicable for the survey of imported health supplements suspected to be contaminated with pharmaceutical ingredients.