An improved dispersive solid-phase extraction coupled with HPLC-MS/MS for the determination of difenoconazole, thiabendazole and their metabolites in animal-derived foods.

The biotransformation and bioaccumulation of pesticide residues in food animals poses significant hazards to the safety of animal-derived food products. However, conventional monitoring primarily focuses on the parent compounds, while the risks associated with their metabolites are frequently neglected. A sensitive multi-residue method was developed and validated for the simultaneous quantification of difenoconazole, thiabendazole, and their key metabolites, difenoconazole-alcohol and 5-hydroxythiabendazole, in six animal-derived food matrices. The analytical procedure involved first extraction of​ the analytes from the matrices with an improved quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, followed by their determination​ via HPLC-MS/MS. Parameters affecting the extraction efficiency were systematically evaluated. Under the optimized conditions, the method demonstrated a limit of detection (LOD) of 0.3-2.0 μg kg-1. The limit of quantitation (LOQ) was set at the lowest spiking level of 2.0 μg kg-1 (except for difenoconazole-alcohol, which is 5.0 μg kg-1). A good linear relationship was observed, with correlation coefficients greater than 0.9993. The accuracy and precision were verified in six matrices (pork, beef, mutton, chicken, duck, and fish), and obtained recoveries ranged from 71.4 % to 104.9 % with relative standard deviations (RSDs) between 2.1 % and 9.8 %. Moreover, the developed method was successfully applied to the determination of pesticide and metabolite residues in market samples, thereby confirming its excellent performance for quantitative analysis in complex animal-derived food matrices.