Identification and analysis of the degradation products of chlorothalonil in vegetables

In this study, the untargeted screening of the degradation products of chlorothalonil (CHT) in vegetables was performed using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). Sulfhydryl-CHT (SH-CHT) and hydroxyl CHT (OH-CHT) were screened as the key degradation products of CHT in vegetables. SH-CHT is a new degradation product of CHT in the vegetables. This study was the first discover the SH-substituted degradation product of pesticide in vegetables. The chemical structure of SH-CHT was deduced and confirmed through synthetic reference. An efficient method for the simultaneous monitoring of SH-CHT and hydroxyl CHT (OH-CHT) in vegetables has been proposed based on QuEChERS in combination with HPLC-MS/MS analysis. The recoveries of SH-CHT and OH-CHT were in range of 85.8%-105.1% with intra- and inter-relative standard deviation (RSD) of less than 10.0%. The limits of detection were 2.0 μg/kg for SH-CHT and 0.2 μg/kg for OHCHT. Seven kinds of vegetables covering various plant families were processed with CHT. As a result, SH-CHT was detected in five kinds of sulfur-rich vegetables with transformation rates of 7.6%-26.6%. OH-CHT was detected in all the vegetables with transformation rates of 1.7%-14.0%. Toxicity evaluation based on ECOSAR program indicated that SH-CHT had potentially high toxicity to aquatic organisms. This study provides a powerful approach for the monitoring and risk assessment of SH-CHT and OH-CHT in food safety control. Furthermore, the study inspires comprehensive research on the overlooked degradation pathways of pesticides in sulfur-rich vegetables.