Analysis of the dissipation kinetics of thiophanate-methyl and its metabolite carbendazim in apple leaves using a modified QuEChERS-UPLC-MS/MS method.

As one of the main fungicides for the apple leaf disease control, thiophanate-methyl (TM) mainly exerts its fungicidal activity in the form of its metabolite carbendazim (MBC), whose dissipation kinetics is very distinct from that of its parent but has been paid little attention. The aim of this work was to investigate the dissipation kinetics of TM and its active metabolite MBC in apple leaves using a modified QuEChERS-UPLC-MS/MS method. The results showed that TM and MBC could be quickly extracted by this modified QuEChERS procedure with recoveries of 81.7-96.5%. The method linearity was in the range of 0.01-50.0 mg kg-1 with the quantification limit of 0.01 mg kg-1 . Then this method was applied to the analysis of fungicide dissipation kinetics in apple leaves. The results showed that the dissipation kinetics of TM for the test in 3 months can be described by a first-order kinetics model with a DT50 (dissipation half-life) range of 5.23-6.03 days and the kinetics for MBC can be described by a first-order absorption-dissipation model with the Tmax (time needed to reach peak concentration) range of 4.78-7.09 days. These models can scientifically describe the behavior of TM and MBC in apple leaves, which provides necessary data for scientific application.