Determination of Residues of Cyflumetofen and Bifenazate on Citrus and Dietary Risk Assessment by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Cyflumetofen and bifenazate are widely used as high-efficiency agents in citrus cultivation. Their residues and metabolic patterns are closely related to food safety and human health. Therefore, establishing accurate and sensitive residue detection methods is essential for agricultural product quality monitoring. In this study, an ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination of residues of the two acaricides (2-trifluoromethylbenzoic acid, bifenazate-diazene) and their metabolites in citrus fruits. The samples were extracted with acetonitrile, and purified by salt precipitation. Chromatographic separation was performed an ACQUITY UPLC^® BEH C18 column using a mobile phase consisting of methanol and 0.1% formic acid aqueous solution with gradient elution. Mass spectrometric detection was performed under both positive and negative ion modes with multiple reaction monitoring, and quantitative analysis was performed using the external standard method. The results showed that the target analytes and their metabolites exhibit good linearity within the range of 0.005-0.5 mg/L (R²>0.997 4). At low, medium and high spiked concentration levels, the average recoveries of cyflumetofen, 2-trifluoromethylbenzoic acid, bifenazate and bifenazate-diazene are 76.4%-96.4%, 91.6%-108.5%, 84.0%-107.0%, 94.2%-112.0%, while their relative standard deviations are 2.0%-5.0%, 1.3%-7.0%, 0.5%-8.8% and 0%-4.1%, respectively. The limit of quantification (LOQ) for all four species is 0.01 mg/kg. This method was applied for the analysis citrus pulp and whole-fruit samples collected from 12 major citrus-producing regions in China at 14 and 21 days after harvesting. The results indicated that the residual concentration of cyflumetofen and 2-trifluoromethylbenzoic acid, and the total residue concentration of cyflumetofen and 2-trifluoromethylbenzoic acid (calculated as cyflumetofen) are <0.080, <0.01, and <0.10 mg/kg, respectively, and the residual concentration of bifenazate and the total residue level of bifenazate and binfenazate-diazene (calculated as bifenazate) are <0.16 and <0.37 mg/kg, respectively. Dietary risk assessment showed that the national estimated daily intake (NEDI) and risk entropy (RQ) for the general population are 0.0279 mg and 0.4% for cyflumetofen, and 0.119 mg and 18.9% for bifenazate. This result indicates that the residues of cyflumetofen and bifenazate in citrus poses no unacceptable risks to humans.