The Effects of Formulation on Imidacloprid Dissipation in Grapes and Vine Leaves and on Required Pre-Harvest Intervals under Lebanese Climatic Conditions

Abstract

In this study, imidacloprid, a systemic insecticide, currently having a specified European Commission MRL value for vine leaves (2 mg kg−1), was applied on a Lebanese vineyard under different commercial formulations: as a soluble liquid (SL) and water dispersible granules (WDG). In Lebanon, many commercial formulations of imidacloprid are subject to the same critical good agricultural practice (cGAP). It was, therefore, important to verify the variability in dissipation patterns according to matrix nature and formulation type. Random samplings of grapes and vine leaves were performed starting at 2 days until 18 days after treatment. Residue extractions were performed according to the QuEChERS method and the analytical determination using liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS). The SL formulation yielded significantly higher initial deposit than the WDG formulation on grapes and vine leaves. The formulation type did not significantly affect the dissipation rates; the estimated half-lives in grapes and vine leaves were 0.5 days for all imidacloprid formulations. No pre-harvest intervals were necessary on grapes. PHIs of 3.7 days for the SL formulation and 2.8 days for the WDG formulation were estimated on vine leaves. The results showed that the type of formulation and the morphological and physiological characteristics of the matrix had an effect on the initial deposits, and thus residue levels, but not on the dissipation patterns.

Dissipation kinetics, decontamination and dietary risk assessment of imidacloprid residue in bitter gourd and soil

“…The phytochemical properties of imidacloprid viz., water solubility (0.61 g/L at 20 °C), vapor pressure (3 x 10 -12 mmHg at 20 °C), octanol/water partition coefficient (Kow) (pH 7 -0.57 at 21 °C) and Henry's constant (1.7 x 10 -10 Pa•m 3 /mol) (Pesticide Properties DataBase, 2022). Imidacloprid residues in crops like mango, grapes, okra, potato, cucumber, strawberry, apple and soil have been quantified using Liquid chromatography with tandem mass spectrometry (LC-MS/MS), High-performance liquid chromatography (HPLC), Gas chromatography mass spectrometry (GC-MS) and Liquid chromatography with mass spectrometry (LC-MS) (Malhat et al, 2021;Hendawi et al, 2018;Majed et al, 2021;Mohapatra et al, 2012;Sahoo et al, 2012). While previous research estimated imidacloprid residues on different crops, no systematic study has been carried out on the dissipation kinetics, decontamination and risk assessment of imidacloprid in bitter gourd.…”