Residual dynamics of three organophosphorus pesticides in Agaricus bisporus fruits and cultivation substrates

To investigate the residual behaviors of three organophosphorus pesticides in the cultivation of Agaricus bisporus, field trials were conducted by applying diazinon, chlorpyrifos and phoxim into the culture media (soil and substrates). By optimizing the pretreatment method and instrument conditions, determination method of three organophosphorus pesticide in mushroom, soil and substrates using liquid chromatography-tandem mass spectrometry was established. Samples were extracted with acetonitrile, purified by QuEChERS and detected with UPLC-MS/MS. In mushroom, soil and cultivation substrates, Recoveries of diazinon at the spiked levels of 0.0003, 0.003, 0.1 mg/kg and the recoveries of chlorpyrifos and phoxim at the spiked levels of 0.0006, 0.006, and 0.1 mg/kg, were 76%-108%, and the relative standard deviation was 2.2%-13%. The limits of detection (LOD) of diazinon, chlorpyrifos and phoxim were 0.0001, 0.0002, 0.0002 mg/kg, respectively, and the limits of quantitation (LOQ) were 0.0003, 0.0006, 0.0006 mg/kg, respectively. At all application rates, three pesticides dissipated following the first-order degradation kinetics. The dissipation half-lives of diazinon, chlorpyrifos and phoxim in cultivation substrates were 5.2 d, 10.6 d, 13.6 d and 5.6 d, 11.4 d, 12.3 d and those in soil were 25.9 d, 41.7 d, 27.2 d and 41.7 d, 48.1 d, 36.8 d, respectively. The dissipation of three pesticides in soil was faster than that in the cultivation substrates. Chlorpyrifos residue in mushroom fruits was up to 0.014 mg/kg at the application rate of 10 mg/kg, which exceeded the European maximum residue limits standard (MRL). The others were lower than the Japanese, European and America MRL values.