Dissipation behaviors of deltamethrin, emamectin benzoate and hexythiazox in grape under field conditions.

The objective of this study was to evaluate the dissipation kinetics of deltamethrin, emamectin benzoate, and hexythiazox in grapes. The QuEChERS method was employed and validated for the precise determination of these three pesticides using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Excellent linearity was observed with regression coefficients exceeding 0.998. Notably, the limits of quantification (LOQ) were significantly lower than the maximum residue limits (MRLs) established for grapes by the European Union. The QuEChERS method l recovered 93.23% of the pesticides with an acceptable RSD of 5.35% (n = 180), demonstrating its suitability for quantifying them in grapes. Half-lives of deltamethrin, emamectin benzoate, and hexythiazox in grapes were 2.62-2.68 days, 8.15-7.30 days, and 3.24-4.01 days, respectively, for both single and double doses. Residues of all pesticides fell below the MRLs by the preharvest interval. This suggests that their application can be considered safe for grapes, ensuring both pest control and consumer safety.

Dissipation kinetics of some pesticides applied singly or in mixtures in/on grape leaf.

BACKGROUND: Grape and leaf quality are often severely reduced by fungi such as grey rot Botrytis cinerea Pers., powdery mildew Erysiphe necator Schwein, and downy mildew Plasmopara viticola (Berk. & M.A.Curtis) Berl. & De Toni and by insects such as Otiorhynchus spp., European grapevine moth Lobesia botrana Den.-Schiff., vine mealybug Planococcus citri Risso, and grape erineum mite Colomerus vitis Pgst. Various pesticides are often applied to mitigate these pest problems. These chemicals used singly as well as in the form of a mixture can leave residues on or in the crop. It is therefore of great importance to study the dissipation of the pesticides applied alone and in mixtures to this crop to protect consumers. RESULTS: The dissipation kinetics of cypermethrin, boscalid, deltamethrin, kresoxim-methyl, lambda-cyhalothrin, metalaxyl-M, metrafenone, and triadimenol residues were studied in vine leaves grown under sunny conditions in Turkey. The dissipation rate for singly applied pesticides followed first-order kinetics, with half-lifes in grape leaves in the range of 1.85-7.22 days. Changes in the degradation process of pesticide residues were determined after application, as both single applications and mixtures. The degradation of boscalid, cymoxanil, deltamethrin and metalaxyl-M accelerated while the degradation of cypermethrin, kresoxim-methyl, and lambda-cyhalothrin slowed down in mixtures of pesticides. CONCLUSION: The use of pesticides in mixtures leads to slower degradation and higher residues for some active ingredients and faster degradation and fewer residues for other active ingredients. Therefore, pesticide mixtures should not be applied in the field without having detailed information about their ingredients. © 2022 Society of Chemical Industry.

Method validation, residue and risk assessment of 260 pesticides in some leafy vegetables using liquid chromatography coupled to tandem mass spectrometry.

In the present study, QuEChERS method was optimized and validated for determination of 260 pesticides by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The method had a suitable linearity (R2 ≥ 0.99). Limit of detection (LOD) and limit of quantification (LOQ) were ranged from 0.56 to 2.99 µg kg-1 and 1.88 to 9.99 µg kg-1 respectively. Average recoveries varied from 71.14% to 118.83%. Repeatability conditions and intra-laboratory reproducibility conditions of the method expressed as %RSD were found between 0.55% and 16.69% and 0.74% to 19.06%, respectively. The method was used to detect pesticide residue levels of leafy vegetables collected from the open markets, greenhouses and wholesale vegetable market. The pesticide residues were detected in 57.6% of the all samples. In five samples, pesticide residues were above Maximum Residue Levels (MRLs). The risk assessment study for detected pesticides in samples indicated that leafy vegetables consumption was safe for consumers.