Impact of soil type and temperature on dissipation dynamics of a new readymix formulation of halauxifen-methyl + pyroxsulam.

The persistence and dissipation of a new readymix formulation of halauxifen-methyl + pyroxsulam was investigated in three soils viz. red lateritic (Soil A), coastal saline (Soil B) and black soil (Soil C) under three incubation temperatures (20, 30 and 40° C). Soil samples were fortified at 1.0 (T1) and 2.0 (T2) mg kg- 1 doses separately for both compounds. The analytical methods showed satisfactory mean recovery, precision and linearity and therefore accepted for analysis. Both molecules followed single first-order kinetics. A significant influence of soil type on the persistence of both herbicides was observed. The order of stability of halauxifen-methyl was Soil A > B > C and for pyroxsulam was Soil B > C > A. Besides, a faster rate of dissipation of halauxifen-methyl and pyroxsulam was recorded at elevated temperatures, regardless of soil type. This research will help to understand the effect of temperature on the fate of the herbicide mixture in soils of diverse agro-climatic regions.

Effect of Soil Type and Temperature on Persistence and Dissipation Kinetics of a New Readymix Formulation of Fomesafen + Quizalofop-ethyl.

The research portrays the fate of a new herbicide mixture of fomesafen and quizalofop-ethyl. The soil samples viz. red lateritic soil (A), coastal saline soil (B) and black soil (C) were fortified separately for fomesafen and quizalofop-ethyl at 0.5 (T1) and 1.0 mg kg-1 (T2) doses and incubated at 20, 30 and 40°C. A satisfactory mean recovery, precision and linearity proved that the methods were accurate. Both the herbicides followed first + first order kinetics. Higher persistence of fomesafen was observed in Soil C than Soil B and Soil A with 22.38-53.75 days half-life, whereas quizalofop-ethyl showed higher stability in Soil A than Soils B and C with half-life of 0.93-12.07 days. Both compounds showed faster rates of dissipation at increased temperature, irrespective of soil type. The current study will help to predict the effect of temperature on the dissipation of herbicides in different soil under real field scenario.

Effect of pH on the Hydrolytic Transformation of a New Mixture Formulation of Fomesafen and Quizalofop-ethyl in Water.

A hydrolytic transformation study was conducted in water of pH 4.0, 7.0 and 9.2 to evaluate the effect of pH on persistence of a new readymix formulation of fomesafen and quizalofop-ethyl. The water samples were fortified at 0.5 and 1 µg mL-1 levels and analysed at 0 (2 h), 1, 3, 7, 15, 30, 60, 90, 120, 150 days interval. Both the analytical methods were validated following SANTE guideline and found accurate based on average recovery of 80-100%, Relative standard deviation (RSD) < 20% and Coefficient of Determination (R2) 0.99. The dissipation of both the molecules was pH dependent and followed first order kinetics. Higher persistence of fomesafen was observed in alkaline pH as compared to neutral and acidic pH with half-life of 41.56-63.24 days, whereas higher stability of quizalofop-ethyl was observed in the water of acidic pH followed by neutral and alkaline pH with half-life of 1.26-8.09 days.

Validation of a Multiresidue Method for the Analysis of 86 Multiclass Pesticides in Litchi Fruit by Gas Chromatography-Tandem Mass Spectrometry.

BACKGROUND: Although India is an important producer of litchi fruit, there is hardly any validated method available for its pesticide residue analysis. This strongly warrants the need to standardize a simple multiresidue analytical method for efficient analysis of multiclass pesticides with specificity, sensitivity, and accuracy in a single chromatographic run in combination with MS determination. OBJECTIVE: The aim of this study was to develop and validate a rapid ethyl-acetate-based sample preparation method for a simultaneous determination of 86 pesticides in litchi fruit by using GC-tandem MS. METHODS: The method involved ethyl acetate as an extracting solvent and a combined salt system comprising sodium chloride and sodium sulphate for the organic layer separation. To obtain satisfactory recovery percentage of each pesticide studied here, this combination was selected for further validation based on selectivity, sensitivity, linearity, precision, and accuracy values. RESULTS: The correlation coefficient (r2) of studied pesticides ranged between 0.97 and 0.99 at six concentration levels from 5 to 250 ng/mL. Furthermore, the average recovery values were within 70 and 120%, with repeatability relative SD below 20% for all 86 pesticides at the LOQ level and with an appreciable Horwitz ratio distribution that ranged between 0.5 and 2. CONCLUSIONS: All data demonstrate that the proposed method is adequately linear, accurate, and repeatable. Therefore, it can be widely used in commercial laboratories for analyzing pesticide residues for both domestic and export purposes. The method is in support of protecting consumer health. HIGHLIGHTS: A large-scale multiresidue method is reported for simultaneous analysis of a wide range of pesticides in litchi. The method complies with the regulatory requirements in terms of sensitivity for maximum residue limit compliance. The performance of the method complied with the SANTE guidelines of analytical QC.

Effect of pH on the Transformation of a New Readymix Formulation of the Herbicides Bispyribac Sodium and Metamifop in Water.

A laboratory experiment was conducted to investigate the effect of pH on the persistence and the dissipation of the new readymix formulation of bispyribac sodium and metamifop. The experiment was conducted in water of three different pH viz. 4.0, 7.0 and 9.2. The spiking level of both the compounds in water was 1.0 and 2.0 µg/mL. The residues were extracted by a simple, quick and reliable method and quantified by liquid chromatography tandem mass spectrometry (LC-MS/MS). The method was justified based on the recovery study, which was > 85%. The dissipation of both compounds followed first order kinetics. The half-life values ranged between 19.86-36.29 and 9.92-19.69 days for bispyribac sodium and metamifop, respectively. The pH of water has a prominent effect on degradation of both the compounds. The rate of dissipation of both the compounds was highest in water of acidic pH followed by neutral and alkaline pH.