Effect of decontamination and processing on insecticide residues in grape (Muscat Hamburg).

Field and laboratory experiments were conducted to study the effect of simple decontamination methods and processing on imidacloprid, dimethoate, and emamectin benzoate residues in grapes and their processed products by liquid chromatography-mass spectrometry. Among the decontamination methods evaluated, washing with NaCl (2%) solution was effective for reducing imidacloprid (77.55%), dimethoate (83.27%), and emamectin benzoate (77.28%) residues in mature grapes. No metabolites (omethoate and 6-chloronicotinic acid) were detected in both decontamination and processing studies. The grapes were processed into various products, including fresh juice, squash, and raisin, following the standard effective steps for each product. Washing with NaCl (2%) solution for decontamination was included as an additional step in the standard protocol and resulted in substantial removal of surface residues of the selected insecticides. The processing factor calculated was less than one for all the products.

Bifenthrin in the tropical sugarcane ecosystem: persistence and environmental risk assessment.

Termites are one of the major pests of sugarcane. Bifenthrin has label claim for use against sugarcane termites and is applied at the time of planting over the cane setts in the furrows. A thorough knowledge on the dissipation kinetics of bifenthrin in the soil and cane setts provides an insight into its dynamic behavior in the soil-plant-environment continuum, and hence, was studied in detail. The recoveries of the method adopted to determine the residues of bifenthrin in the soil, sugarcane setts, stem, and leaf were in the range of 92.78-98.19% at three levels of fortification ranged between 0.01 and 0.1 µg/g of matrix. At the recommended dose (100 g a.i./ha), bifenthrin was found to persist in the soil and cane setts up to 60 and 75 days after treatment (DAT) with the half-lives of 16.4 and 25.0 days, respectively. The dissipation kinetics of bifenthrin followed the biphasic model. At double the recommended dose, the residues persisted up to 75 DAT and reached below the detectable limit (< 0.01 µg/g) on 90 DAT both in the soil and setts. The half-life of bifenthrin was 22.0 days in the sandy clay loam soil and 17.6 days in/on the sugarcane setts. In the present study, dissipation by photolysis has been ruled out, as the treated setts were not exposed to sunlight. This could be one of the reasons for longer persistence of bifenthrin in the sugarcane setts up to 75 DAT with the half-life of more than 2 weeks. The bifenthrin residues were not detected in the leaf and stem of sugarcane plant throughout the experimental period. There could be harmful effects to earthworms (risk quotient > 1.0) due to the presence of bifenthrin residues in the soil of tropical sugarcane ecosystem.

Persistence and metabolism of carbofuran in the soil and sugarcane plant.

Persistence and metabolism of carbofuran in the soil and sugarcane plant were studied under tropical sugarcane ecosystem. Residues of carbofuran and its metabolites in the soil, sugarcane leaf, and juice were determined by employing matrix-specific sample preparation methods and gas chromatography equipped with mass spectrometry. The recoveries of carbofuran, 3-keto carbofuran, and 3-hydroxy carbofuran were in the range of 88.75 ± 2.58-100.25 ± 2.38, 90.38 ± 2.61-98.24 ± 4.78, and 89.25 ± 3.11-98.10 ± 3.19%, respectively, at three levels of fortification across the three matrices involved in the study. At recommended dose (carbofuran 3% CG at 2 kg a.i./ha), the initial deposit of carbofuran in the soil was 14.390 ± 1.727 µg/g. The total residues comprising both carbofuran and 3-hydroxy carbofuran were detected up to 105 days after treatment with the half-life of 10.83 days. The parent compound and its metabolite were detected and quantified in the sugarcane plant (leaves and juice) from 14 days after application of carbofuran in the soil. The total residues (carbofuran and 3-hydroxy carbofuran) were detected in the leaves and cane juice up to 75 and 30 days after treatment, respectively.

Dissipation kinetics and safety evaluation of tebuconazole and trifloxystrobin in tea under tropical field conditions.

Dissipation kinetics of tebuconazole, trifloxystrobin and its acid metabolite residues were studied in tea under tropical field conditions using GC-MS (SIM). The average recoveries ranged from 80.7% to 105.8%, with a RSD of <9.3%. Dissipation rate for both doses applied followed first-order kinetics, with half-lives in green leaves in the range of 2.8-3.3 and 2.9-3.3 days; ranges in processed tea were 2.7-3.6 days for trifloxystrobin and 3.0-3.1 days for tebuconazole. The trifloxystrobin residues were not transferred into the tea infusion during the infusion process; tebuconazole did transfer, in the range of 14.3-18.9%. As the theoretical maximum residue contributions on tea from initial deposits were found to be less than the maximum permissible intake values, at the recommended application dose a withdrawal period of 23 days before consumption should be applied to reduce risk.

Dissipation behavior of phorate and its toxic metabolites in the sandy clay loam soil of a tropical sugarcane ecosystem using a single-step sample preparation method and GC-MS.

The dissipation of phorate in the sandy clay loam soil of tropical sugarcane ecosystem was studied by employing a single-step sample preparation method and gas chromatography with mass spectrometry. The limit of quantification of the method was 0.01 µg/g. The recoveries of phorate, phorate sulfoxide, phorate sulfone, and phorate oxon were in the range 94.00-98.46% with relative standard deviations of 1.51-3.56% at three levels of fortification between 0.01 and 0.1 µg/g. The Half-life of phorate and the total residues, which include phorate, phorate sulfoxide and phorate sulfone, was 5.5 and 19.8 days, respectively at the recommended dose of insecticide. Phorate rapidly oxidized into its sulfoxide metabolite in the sandy clay loam soil. Phorate sulfoxide alone accounted for more than 20% of the total residues within 2 h post-application and it was more than 50% on the fifth day after treatment irrespective of the doses applied. Phorate sulfoxide and phorate sulfone reached below the detectable level on 105 and 135 days after treatment, respectively as against 45 days after treatment for phorate residues at the recommended dose. Thus, the reasonably prolonged efficacy of phorate against soil pests may be attributed to longer persistence of its more toxic sulfoxide and sulfone metabolites.

Development and validation of a multiresidue method for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection.

A multiresidue method has been developed and validated for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection. Limits of quantification of the method varied between 0.007 and 0.01 µg/g. Ethyl acetate based extraction followed by dispersive solid-phase extraction cleanup with primary secondary amine yielded internationally acceptable recoveries of acephate, chlorpyrifos, dichlorvos, monocrotophos, malathion, malaoxon, phorate, phorate-sulfoxide, phorate-oxon, phorate-sulfone, and quinalphos from selected matrices. The recoveries of target analytes from cane juice were 75.55 ± 0.5-102.57 ± 4.2, 77.45 ± 4.7-103.33 ± 3.3, and 80.55 ± 6.6-105.82 ± 9.8% at 0.01, 0.02, and 0.1 µg/g levels of fortification, respectively. The recoveries from cane sugar were 73.24 ± 3.5-104.47 ± 1.9, 75.23 ± 1.5-116.10 ± 3.7, and 70.75 ± 5.7-110.15 ± 2.7%, respectively at 0.01, 0.02, and 0.1 µg/g levels of fortification. Matrix effect and measurement uncertainty were within the permissible limit (less than 20%) as prescribed for pesticide residue analysis.

Simultaneous determination of tebuconazole, trifloxystrobin, and its metabolite trifloxystrobin acid residues in gherkin under field conditions.

A rapid, simple, and selective analytical method for the simultaneous determination of tebuconazole, trifloxystrobin, and its metabolite trifloxystrobin acid residues in gherkin and soil was developed and validated by gas chromatography coupled with mass spectrometry. The samples were extracted with acetonitrile and cleaned up by dispersive solid-phase extraction with primary secondary amine sorbent. The limit of quantification of the method was 0.05 mg/kg for all three compounds. The method was validated using blank samples spiked at three levels and recoveries ranged from 83.5 to 103.8% with a relative standard deviation of 1.2 to 4.8%. The developed method was validated and applied for the analysis of a degradation study sample. The residues of trifloxystrobin and tebuconazole were found to dissipate following first-order kinetics with half-life ranging between 3.31-3.38 and 3.0-3.04 days, respectively, for two different dosages. Pesticide residues were below the European Union maximum residue level after seven days for trifloxystrobin (0.2 mg/kg) and ten days for tebuconazole (0.05 mg/kg), which suggested the use of this fungicide mixture to be safe to humans. These results can be utilized in formulating the spray schedule and safety evaluation on trifloxystrobin and tebuconazole in gherkin crop.

A simple and sensitive single-step method for gas chromatography-mass spectrometric determination of fipronil and its metabolites in sugarcane juice, jaggery and sugar.

A simple and sensitive single-step method for gas chromatography-mass spectrometric determination of fipronil and its metabolites viz., fipronil desulfinyl, fipronil sulphide and fipronil sulphone in sugarcane juice, jaggery and sugar has been developed. Acetonitrile was superior to ethyl acetate in terms of selectivity, though they were on par with each other in terms of recoveries. This method does not require any cleanup as the PSA-based cleanup was on par with no-cleanup treatment. Interestingly, the recoveries of fipronil and its metabolites decreased with increased amounts of C18 from 10 to 50mg/g of matrix. Matrix effects were insignificant and the limit of quantification was 0.005µg/g. The recoveries of fipronil and its metabolites varied between 87.5% and 108.5% with the RSD of 0.2-5.3% for all the three matrices studied. This method has also been validated by monitoring fipronil and its metabolites in the retail outlet samples of sugarcane juice, jaggery and sugar.

Dissipation kinetics of chlorantraniliprole in soils of sugarcane ecosystem.

Dissipation kinetics of chlorantraniliprole was studied in sandy loam soils of sugarcane ecosystem by adopting a rapid analytical method. The recovery of chlorantraniliprole was 91.67 % when extracted with ethyl acetate as against only 65.58 % in acetonitrile-based extraction. An additional cleanup step with primary secondary amine did not enhance the recovery significantly over the no-cleanup method. The ethyl acetate-based extraction followed by direct quantification in HPLC (High-performance liquid chromatography) without any cleanup facilitated rapid quantification of chlorantraniliprole residues. The LOQ (limit of quantification) of the method was 0.01 µg/g. The half-life of chlorantraniliprole was 6.50 and 6.81 days for the recommended and double the recommended doses, respectively.