Identification and analysis of the degradation products of chlorothalonil in vegetables

Abstract

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.