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

Abstract

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 DT 50 (dissipation half-life) range of 5.23-6.03 days and the kinetics for MBC can be described by a firstorder absorption-dissipation model with the T max (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.

Dissipation behavior of thiophanate-methyl in strawberry under open field condition in Egypt and consumer risk assessment

“…Different geographical areas, different rainfall, temperature and other environmental factors as well as different crop varieties, and different growing conditions can lead to different half-lives. The half-life values recorded in the present study are similar or lower with the earlier studies conducted in apple, strawberry, cucumber, and grapes were half-lives which are approximately 1.26 in strawberry (Dalia et al 2017), 1 or 5.23-6.03 days in apples (Dalia et al 2017;Wang et al 2019), 4.7-6.5 in grapes (Mandal et al 2010), and 12.3-13.4 days in cucumber (Ali Bassam Al-Obaidie and Sumir 2018).…”

Determination, dissipation dynamics, terminal residues and dietary risk assessment of thiophanate‐methyl and its metabolite carbendazim in cowpeas collected from different locations in China under field conditions

“…The results indicated that the established method provided a relatively better performance in terms of sensitivity and accuracy compared to previous approaches and was acceptable for use in the determination of thiophanate-methyl and carbendazim in cowpea samples. 16,[23][24][25] Dissipation and residue distribution of thiophanatemethyl and carbendazim in cowpeas in field trials The residual definition of thiophanate-methyl is expressed as carbendazim, 43 and the estimated residue concentration of thiophanate-methyl is the sum of the concentrations of thiophanate-methyl and carbendazim, which is termed the 'total carbendazim'. When the residual level is >LOQ, thiophanatemethyl is converted into carbendazim equivalents, and the conversion factor is 0.55.…”

“…For example, the calculated half-lives of thiophanatemethyl at different spraying dosages were 3.6-7.0 days in grapes 16 and 5.26-6.03 days in apple leaves. 25 Terminal residue trials are the data sources for dietary risk assessments and the establishment of maximum residue limits (MRLs) in certain crops. The terminal residue concentrations of thiophanatemethyl and carbendazim in cowpeas are listed in Tables 3 and 4.…”

“…A wide range of studies have been carried out to extract and detect thiophanate-methyl and carbendazim in several matrices using different determination methods, including surfaceenhanced Raman imaging scattering (SERS) techniques, 12 high-performance liquid chromatography (HPLC), [20][21][22] liquid chromatography with tandem mass spectrometry (LC-MS/ MS) 16,23 and ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS). 24,25 For instance, Wen et al 22 developed a salting-out-assisted liquid-liquid extraction coupled with an HPLC approach for the simultaneous determination of thiophanate-methyl and carbendazim and two other benzimidazole fungicides in several different aqueous samples. The limits of detection (LODs) of two target compounds were 0.14-0.19 ng mL −1 , the lowest spiked concentrations were 50 ng g −1 and the recoveries were from 60% to 98%, with relative standard deviations (RSDs) of 1-4%.…”

“…The dissipation of residues and risk assessments of thiophanatemethyl and carbendazim in some crops have been reported previously. 16,[25][26][27][28][29][30] For example, Wang et al 25 developed a modified QuEChERS-UPLC-MS/MS method to determine the concentrations of thiophanate-methyl and carbendazim in apple leaves and investigated the dissipation kinetics of these two analytes. The dissipation followed the first-order model with half-lives of 5.2-6.0 days in apple leaves.…”