A Liquid Chromatographic Method for Determination of Acetamiprid and Buprofezin Residues and Their Dissipation Kinetics in Paddy Matrices and Soil

The present study was conducted to investigate the residue status of two insecticides (acetamiprid and buprofezin) and their dissipation kinetics in three matrices viz. paddy grain, straw and soil. The extraction protocol for residues of these two insecticides was executed using acetonitrile solvent. The analytical method was validated, which showed good linearity with the limit of quantification (LOQ) value of 0.01 and 0.02 mg kg− 1 for acetamiprid and buprofezin respectively. The recovery range was 79.67–98.33 % concerning all the matrices in both the insecticides. Acetamiprid (20% SP) and Buprofezin (25% SC) were applied separately in the paddy field in two doses: single dose (recommended dose) and double dose along with untreated control throughout the experiment. Residue analysis of these two insecticides in paddy (grain and straw) and soil was accomplished employing high-pressure liquid chromatography (HPLC) with a UV detector. The dissipation data showed that acetamiprid exhibited higher dissipation in comparison with buprofezin. However, their persistence was found slightly higher in soil. The dissipation dynamics in the rice and soil were discussed with biological half-lives of both the insecticides. Consumer risk assessment study was also made considering its fate to the consumers.

Plant-Back Intervals of Imicyafos Based on Its Soil Dissipation and Plant Uptake for Rotational Cultivation of Lettuce and Spinach in Greenhouse

The plant-back intervals (PBIs) of imicyafos were investigated for rotational cultivation of lettuce and spinach in greenhouses. Imicyafos dissipation in soil and its plant uptake were evaluated by liquid chromatography-tandem mass spectrometry. Bioconcentration ratios (BCRs) were calculated by comparing the residues in plants to the initial residue in soil. The BCRs were used to calculate the soil acceptable residues (SARs) transferable to plants at the Positive List System (PLS) level. The number of days, PBIs for reaching SARs were obtained from the dissipation equation for imicyafos in soil. In soil, imicyafos followed first order dissipation kinetics (R2 = 0.975) with a half-life of 40.8 days. The BCRs ranged from 0.041 to 0.469 in the edible leaf parts of lettuce and 0.006 to 0.134 in those of spinach. The SARs ranged from 0.021 to 0.244 for lettuce and 0.075 to 1.667 mg kg−1 for spinach. The PBIs of imicyafos were estimated to be 213.9 to 357.3 days for lettuce and 100.8 to 283.6 days for spinach. This study suggests at least a minimum 1-year interval after the final application of imicyafos as a management method that complies with the PLS for the rotational cultivation of lettuce and spinach.