Abstract:

Organophosphorus pesticides (OPs), malathion, methyl parathion, trichlorfon, and acephate were used frequently in vegetable cultivation, mainly metabolized into O,O-dimethyl dithiophosphate, 4-nitrophenol, dimethyl dichloroviny phosphate (DDVP) and methamidophos, respectively. A method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the determination of the organophosphorus pesticides and their metabolites. According to the difference of coloring matter contents in vegetable matrix, the pre-treatment for vegetables with high coloring matter contents were performed using activated carbon coupled with a Florisil solid-phase extraction column, and others were purified by a Florisil solid-phase extraction column. A hydrophilic interaction chromatographic column (ACQUITY UPLC BEH HILIC) was used with acetonitrile-5 mmol/L ammonium acetate as mobile phases. The MS/MS detection was performed under positive or negative electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The results showed that the matrix effect of the LC-MS/MS was 15.3%-45.1%, the recoveries of the four organophosphorus pesticides and their metabolites were 76.9%-102.8%, the precision ranged from 5.92% to 10.19%, the limits of quantification ranged from 0.001 to 0.01 mg/L, and the linear correlation coefficients were 0.9982-0.9999 in the range of 0.01-1.00 mg/L. This method was applied in the analysis of Chinese cabbages, hot peppers, tomatoes and onions from markets. This method can be applied in rapid detection of the organophosphorus pesticides and their metabolites in vegetables.

Key words: liquid chromatography-tandem mass spectrometry (LC-MS/MS), metabolites, organophosphorus pesticides, solid-phase extraction (SPE), vegetables