Simultaneous determination of sulfoxaflor and its metabolites, X11719474 and X11721061, in brown rice and rice straw after field application using LC-MS/MS

The present study was carried out to develop an analytical method for simultaneously detecting and quantifying sulfoxaflor and its metabolites (X11721061, X11719474) in brown rice and rice straw using liquid chromatography-tandem mass spectrometry. The parent compound and its metabolites were extracted and purified using original QuEChERS' method with modification. The matrix-matched calibration curve of sulfoxaflor and its metabolites in both matrices achieved good linearity with determination coefficients (R-2) 0.9944. The overall recoveries of sulfoxaflor at two fortification levels (rice: 0.2 and 1.0mg/kg; rice straw: 0.4 and 2.0mg/kg) ranged from 97.37% to 107.71% with relative standard deviations (RSDs) <5%. On the other hand, the recoveries of both metabolites (X11721061 and X11719474) at 0.1 and 0.5mg/kg (rice) and 0.2 and 1.0mg/kg (rice straw) were satisfactory with values ranging from 83.70 % to 112.60% with RSDs <8%. During storage at -20 degrees C, the analyte and its metabolites were stable for up to 87days. The limits of quantification of 0.02mg/kg were lower than the maximum residue limit (0.2mg/kg) set by the Korean Ministry of Food and Drug Safety for brown rice. The method was successfully applied to paddy field treated with different programme schedules and a preharvest interval of 7days was proposed based upon the current study. In sum, the developed method is accurate and reproducible for ensuring the reliable determination of sulfoxaflor (and its metabolites) in harvested rice grain and straw samples from the field. The residual level of parent compound does not seem to pose any hazardous effect and treated rice could be safely used for consumption.