Simultaneous Determination of Seven Adulterants in Slimming Functional Foods by HPLC–ESI–MS/MS

Abstract

A high-performance liquid chromatography–electrospray ionization–tandem mass spectrometric method for simultaneous determination of seven adulterants including pseudoephedrine, norpseudoephedrine, caffeine, strychnine, fenfluramine, sildenafil, and amfepramone in slimming functional foods was established. For tablet formulation, the target chemicals were extracted with ammoniated methanol, while for liquid samples, plant powder, or capsules formulations, these chemicals were extracted with a mixture solution of ammoniated methanol-diethyl ether (2:1 v/v). After anhydrous sodium sulfate being added, the extracts were centrifuged and then the supernatant was evaporated to dryness under condition of a nitrogen gas flow. The residue was reconstituted with acetonitrile–water (1:9 v/v) to produce a test solution. Chromatographic separation was accomplished using a RP-C18 column with a gradient elution procedure using 0.03% formic acid in acetonitrile and 0.01% formic acid solution. Seven chemicals were separated and detected in 10 min. Clenbuterol was used as an internal standard. The recoveries of seven targeted chemicals in different formulations are from 81.2% to 110.3%. Limits of detection of the method are from 4.2 to 16.7 μg kg−1 with relative standard deviations of 1.1–8.4%. The linearity of the method ranges from 2.0 to 500 ng mL−1 for all chemicals, with linear correlation coefficients varying from 0.9982 to 0.9992. The method has been used for determining the target chemicals in nine slimming functional foods, and satisfactory results are achieved. Among these tested samples, norpseudoephedrine and fenfluramine were not detected for all samples. Some other components, such as pseudoephedrine, amfepramone, strychnine, and sildenafil were detected in one or more samples, while caffeine was detected in almost all of these tested samples.