Simultaneous determination of difenoconazole and pyraclostrobin residues in potatoes based on UPLC-MS/MS and their...

The combined application of difenoconazole and pyraclostrobin is a common strategy to combat early blight in potatoes; however, a comprehensive understanding of their co-residue behavior and associated dietary risks remains limited. In this study, a modified QuEChERS method coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed and validated for the simultaneous determination of difenoconazole and pyraclostrobin residues in potatoes. The calibration curves showed excellent linearity over the concentration range of 0.002-0.2 mg/L. At fortification levels of 0.02, 0.2, and 2 mg/kg, the average recoveries of difenoconazole ranged from 94.8 to 100.4%, with relative standard deviations (RSDs) of 0.56-1.81%; the average recoveries of pyraclostrobin ranged from 95.2 to 99.8%, with RSDs of 0.97-1.62%. The limit of quantification (LOQ) of both compounds was 0.02 mg/kg, and the instrumental limit of detection (LOD) was 2.00 × 10 g. This sensitivity is substantially better than that of conventional HPLC-UV methods (which typically exhibit LODs around 10^-9 g), and the LOQ aligns with the maximum residue limit (MRL) of 0.02 mg/kg established in China. Dietary risk assessment indicated that the risk quotients (RQs) were 0.993 and 0.956 for difenoconazole and pyraclostrobin, respectively, demonstrating that the health risks to consumers are acceptable.