Residual estimation of spirotetramat and its metabolites in chilli and soil by LC-MS/MS.

Two applications of spirotetramat were done to study the dissipation and persistence of spirotetramat and its four different metabolites in chilli and soil at 10 days interval. Total spirotetramat residues were estimated by LC-MS/MS instrument. The mean initial deposits of total spirotetramat after application of spirotetramat 15.31 OD @ 60 (X dose), 75 (1.25 × dose) and 120 (2 × dose) g a.i. ha-1 on green chilli were found to vary from 0.38 to 0.83 mg kg-1 during the initial year. Spirotetramat and its metabolite residues in green chilli were found to be below limit of quantification (0.01 mg kg-1) after 15 days of application. The spirotetramat cis enol (the major metabolite) was formed in both the soil and the plant. The residues of spirotetramat-monohydroxy were below LOQ irrespective of any substrate during the estimation. In soil, the total initial spirotetramat deposits for the 1st year were found 0.09 for X dose, 0.12 for 1.25 × dose and 0.20 mg kg-1 for 2 × dose. After 3 days for both X and 1.25 × doses and 5 days for 2 × dose, the total spirotetramat residues were below LOQ. The spirotetramat's half-life values have been determined to be between 3.19 and 3.93 days and 1.00 and 1.59 days, respectively, in soil and green chilli fruits. One day waiting period is proposed for the safe consumption of green chilli when the spirotetramat was applied irrespective of the dose.

Dissipation kinetic study of fenazaquin in chilli and soil by LC-MS/MS.

Dissipation and persistence of fenazaquin residues in chilli and soil were studied for 2 years following two applications of fenazaquin at 10-day interval. The limit of detection and limit of quantification were 0.003 and 0.01 mg kg-1. The mean initial deposits of fenazaquin 10 EC on green chilli fruits were found to be 0.74, 1.17, and 1.79 mg kg-1 after the application @ 125 (X dose), 156.25 (1.25X dose), and 250 (2X dose) g a.i. ha-1, respectively, during the first year followed by 0.78, 1.20, and 1.70 mg kg-1, respectively, during the next year. The mean initial deposits in soil were found to be 0.18, 0.25, and 0.44 mg kg-1 for the X, 1.25X, and 2X doses, respectively, during the first year and 0.19, 0.22, and 0.39 mg kg-1, respectively, during second year. The residues of fenazaquin in green chilli dissipated above 96% at 20 days in the three different doses whereas in red chilli, the residues were present on 25 days and at maturity, residues were below the limit of quantification (LOQ). In soil, the residues dissipated below the LOQ at 15 days for X and 1.25X while 20 days for the 2X dose, respectively. The half-life values in green chilli fruits and soil for the fenazaquin were found to be in the range of 3.22-3.93 days and 2.41-3.35 days, respectively. The waiting period was calculated to be 3, 5, and 8 days for green chilli after the application of fenazaquin at 25, 156.25, and 250 g a.i. ha-1, respectively.

Validation of QuEChERS Method for Estimation of Imidacloprid and its Metabolites in Cotton Flower, Pollen, Nectariferous Tissue, and Honey.

BACKGROUND: Exposure of Apis mellifera to neonicotinoid insecticides is one of the factors attributed to the recent decline in A. mellifera populations resulting in economic and ecological losses due to loss of pollination services. Honeybees can get exposed to neonicotinoids like imidacloprid directly in the field at the time of application as well as during consumption of pollen and nectar from treated plants. In addition, some metabolites of imidacloprid are more toxic than the parent compound. So, the fate of imidacloprid and its metabolites in commodities to which honeybees get exposed needs to be overhauled. OBJECTIVE: To validate QuEChERS method for estimation of imidacloprid and its metabolites in cotton flower, pollen, nectariferous tissue, and honey using HPLC. METHODS: The QuEChERS method was validated in terms of selectivity, linearity, LOD, LOQ, matrix match, accuracy, and precision. The estimation of residues was done by HPLC. RESULTS: Recoveries of imidacloprid and its metabolites for cotton flowers, nectariferous tissue, pollen and honey samples were in the range of 80.42-99. 83%. LOQ for imidacloprid and its metabolites was 0.01 µg/g. Acceptable precision (RSD < 20%) was obtained. CONCLUSION: The method allows simple and fast extraction of imidacloprid and its metabolites from cotton flower, pollen, nectariferous tissue, and honey. HIGHLIGHTS: An accurate, simple, and sensitive analytical method was validated for imidacloprid and its metabolites. The method was validated according to the SANTE/12682/2019 guidelines.

Dissipation kinetics of imidacloprid in cotton flower, nectariferous tissue, pollen and Apis mellifera products using QuEChERS method.

BACKGROUND: Exposure of Apis mellifera to neonicotinoid insecticides is one of the factors attributed to the recent decline in A. mellifera populations resulting in economic and ecological losses due to loss of pollination services. Honey bees can get exposed to neonicotinoids like imidacloprid directly in the field at the time of application as well as during consumption of pollen and nectar from treated plants. So, the fate of imidacloprid in commodities to which honey bees get exposed needs to be overhauled. RESULTS: Residue of imidacloprid was investigated following imidacloprid application as seed treatment (2.4 and 4.8 g a.i. kg-1 seed) at the time of sowing and as foliar spray (17.8 and 35.6 g a.i. ha-1 ) at 70 days after sowing when the crop was at full bloom stage. The imidacloprid residue was below limit of quantification (LOQ) in flowers, necatariferous tissue, pollen from seed-treated cotton plants and honey collected from hives kept in plots with seed-treated cotton plants. However, average initial imidacloprid residue (2 h after spray) was 1.84 and 1.95 mg kg-1 in flowers; 0.22 and 0.24 mg kg-1 in nectariferous tissue; 0.88 and 0.96 mg kg-1 in pollen collected from plants sprayed with imidacloprid @ 17.8 g a.i. ha-1 at locations Faridkot and Bathinda, respectively. The average initial imidacloprid residue (21 days after spray) in honey collected from hives was 0.01 mg kg-1 . CONCLUSION: The residue in different substrates sampled from seed treated cotton plants was below LOQ. However, its foliar spray at bloom time resulted in imidacloprid residue in flower, nectariferous tissue, pollen and honey sampled from hives placed in plots. © 2021 Society of Chemical Industry.

Validation of QuEChERS Method Coupled with LC-MS/MS for Determination of Thiamethoxam and its Metabolites in Wheat and Soil.

BACKGROUND: Thiamethoxam, a neonicotinoid insecticide, has been widely accepted for the control of sucking and certain chewing pests. Through different routes, i.e., wind drift, leaching, and surface runoff, it can reach non-target areas, which include humans as well. Therefore the fate of thiamethoxam in food grains and soil is of prime importance, entailing a need for pesticide use to be subject to steady observation. OBJECTIVE: The review aimed to validate the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for the detection of thiamethoxam and its metabolites in wheat leaves, grain, straw, and soil using liquid chromatography-tandem mass spectrometry (LC-MS/MS). METHOD: The QuEChERS method allows sample extraction by acetonitrile followed by cleanup with a primary secondary amine sorbent, magnesium sulphate, and graphitized carbon black. The method was validated in terms of selectivity, linearity, LOD, LOQ, matrix match, accuracy, and precision. The estimation of residues was done by LC-MS/MS. RESULTS: The recovery of thiamethoxam and its metabolites in wheat and soil samples was in the range of 81.22-98.14%. The LOQ for thiamethoxam and its metabolites was 0.01 mg/kg. The matrix effect values were in the acceptable range of -20 to +20%. CONCLUSIONS: The method allows a simple and fast extraction of thiamethoxam and its metabolites from wheat leaves, grain, straw, and soil. It could be helpful in the evaluation of regulatory and food safety decisions regarding the use of neonicotinoids. HIGHLIGHTS: The method was validated according to the European Commission SANTE/12682/2019 guidelines. An accurate, simple, and sensitive analytical method was validated for thiamethoxam and its metabolites.