Monitoring hexythiazox residues in vegetables using LC-MS/MS: Dissipation kinetics, terminal residues, risk assessment, and washing efficiency

This study evaluated the dissipation behavior, final residues, dietary exposure risk, and removal efficiency of hexythiazox in greenhouse-grown tomatoes, cucumbers, and peppers. Field applications were conducted at two dosage levels (50 and 100 g a.i./ha), with samples collected over 14 days. Residue quantification was performed using a modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction method coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS), which was validated according to the SANTE/11312/2021 guidelines. The method demonstrated satisfactory linearity, sensitivity, accuracy, and precision across all matrices. Hexythiazox dissipation followed first-order kinetics, with half-lives ranging from 1.47 to 2.41 days. Pre-harvest intervals (PHIs) varied by crop and dose, from 3.79 to 11.78 days. Chronic dietary risk assessment showed hazard quotient (%HQ) values below the 100% threshold, indicating minimal long-term consumer risk. Postharvest rinsing with tap water (2-5 min) effectively reduced residues by up to 86.76% in tomatoes, 74.46% in cucumbers, and 65.17% in peppers. Although washing brought tomato residues below EU Maximum Residue Limits (MRLs), those in cucumbers and peppers, particularly at higher doses, remained above regulatory limits. These results underscore the importance of crop-specific residue management and postharvest decontamination practices in ensuring food safety.