Determination of Residual Behavior of Flufenacet in Wheat and its Dietary Risk Assessment by Liquid Chromatography-Tandem Mass Spectrometry

A method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the determination of flufenacet and its metabolites in wheat. The results showed that the linear relationship of flufenacet and its metabolites is good in the concentration of 0.001-0.5 mg/L, and the correlation coefficient is greater than 0.999. In three different concentration levels, the recoveries of flufenacet, flufenacet thioglycolate sulfoxide, flufenacet OA and flufenacet ESA in wheat are 89.1%-119.4%, 70.7%-113.0%, 72.0%-105.3%, 74.1%-114.8% with the relative standard deviations (RSDs) range of 0.5%-3.1%, 2.2%-5.6%, 1.6%-3.4%, 1.4%-5.9%, respectively. The limits of quantitation (LOQs) of flufenacet and flufenacet thioglycolate sulfoxide, flufenacet OA and flufenacet ESA are 0.01, 0.05 mg/kg, respectively. The method was used to determine the wheat samples in ten areas. During the harvesting, the residues of flufenacet and flufenacet thioglycolate sulfoxide in wheat grains and stalks period are all less than 0.010 mg/kg, flufenacet OA are 0.050-0.38 mg/kg, flufenacet ESA are less than 0.050 mg/kg, and the total residues of flufenacet are less than 0.12-0.69 mg/kg. Dietary risk assessment was calculated according to the dietary risk assessment model. The results showed that the daily intake (NEDI) of flufenacet in winter wheat for general population is 0.02687 mg, and the risk entropy of flufenacet is 8.5%, indicating that the dose of flufenacet in wheat does not pose an unacceptable risk to the health of the general population. There are some uncertainties in risk assessment, which are mainly reflected in three aspects: 1) No chlorine-related information has been collected from the database of the FAO/WHO Joint Meeting on Pesticide Residues, and no reference dose has been found, so acute dietary intake risk assessment cannot be carried out. 2) The maximum residue limit of registered crops in various countries was used for the residual data of flufenacet, and the median residue value could not be obtained, and the processing factor of cooking process was not considered, so the calculated risk entropy was high. 3) In this paper, only wheat was used as a single exposure route to exposure, while daily residents were also exposed to flufenacet through other foods, so there are still some limitations in the overall risk assessment of flufenacet exposure for residents.