Determination of 18 Organophosphorus Pesticide Residues in Hedyotis Diffusa by QuEChERS Coupled with Gas Chromatography-Triple Quadrupole Mass Spectrometry

A metod of QuEChERS-gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) for the determination of 18 organophosphorus pesticides (OPPs) in Hedyotis diffusa was established. The target compounds in the sample were extracted with acetonitrile, the water was removed with anhydrous magnesium sulfate, and the impurities were removed with a mixture of ethylenediamine-N-propyl silane, C₁₈ adsorbent, and graphitized carbon black. The solution obtained was used for GC-MS/MS analysis. Rxi-5 Sil MS capillary chromatographic column was used to separate target compounds in sample solution under temperature-programmed condition, MS with electron impact ion source was used for detection in multiple reaction monitoring mode, and a series of mixed standard solutions with blank sample solution as dilution solvent was used to make working curves. The results showed that mass fractions of 18 OPPs were linearly related to the corresponding peak areas in the range of 10.0-1 000.0 μg·kg^-1, with detection limits (3S/N) in the range of 0.6-3.0 μg·kg^-1. The spiked recovery test was made on the negative samples, giving recoveries in the range of 90.3% to 99.9%, and RSDs (n=6) of determined values were ranged from 1.0% to 3.6%. This proposed method was used for the analysis of actual samples, and ethionate, malathion, triazophos and pyridaben were detected, with detection amount in the range of 0.2-19.4 μg·kg^-1.