Determination of organophosphorus pesticides in Lycium barbarum by gas chromatography with flame photometric detection.

An analytical method was developed to determine 14 organophosphorus pesticide residues in Lycium barbarum, which is both a botanical medicine and a food. A 5 g sample is mixed with 10 mL ethyl acetate and, after shaking and centrifuging, 5 mL of the upper layer is removed, concentrated, and analyzed by gas chromatography (GC) with flame photometric detection. The essential feature of this method is that, for the purpose of reducing the burden of the GC system, 0.01 g activated carbon is used to absorb pigments during the cleanup procedure. Average recoveries of 14 organophosphorus pesticides added at 0.05, 0.1, and 0.5 mg/kg were 66.84-102.42, 71.07-97.93, and 62.50-96.24%, respectively. Limits of detection ranged from 5 to 15 microg/kg. The identities of the 14 pesticides were confirmed by GC/mass spectrometry detection in the selected-ion monitoring mode. This method is sensitive, simple, rapid, inexpensive, and safe.