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Dissipation and residue fate of kresoxim-methyl in tobacco leaves and soil under field conditions

Nie, Yanhua, Zhang, Kankan, Chen, Hongyu, Zhang, Wen, Zhu, Huijun, Hu, Deyu
International journal of environmental analytical chemistry 2015 v.95 no.14 pp. 1338-1352
detection limit, ecosystems, field experimentation, gas chromatography, half life, kresoxim-methyl, leaves, petroleum, soil, tobacco, China
The fate of kresoxim-methyl was studied in a tobacco field ecosystem, and a simple and reliable method was developed for the determination of kresoxim-methyl in soil, green and cured tobacco leaves. Kresoxim-methyl residues were extracted from samples with petroleum ether, and determined by gas chromatography (GC) coupled with an electron capture detector (ECD). Kresoxim-methyl (30% suspension concentration) was applied at 150 g a.i. ha –¹ (the recommended high dosage) and 225 g a.i. ha –¹ (1.5 times the recommended high dosage) in the experimental fields in Huishui and Changsha in China. The limits of detection (LODs) and limits of quantification (LOQs) of kresoxim-methyl in green tobacco leaves, cured tobacco leaves and soil were 0.012 and 0.04 mg kg –¹, 0.12 and 0.4 mg kg –¹, and 0.0015 and 0.005 mg kg –¹, respectively. The average recoveries were 84.5% to 95.7%, 79.8% to 94.3% and 83.3% to 93.8% with relative standard deviations (RSDs) less than 10% in green tobacco leaves at four spiked levels (0.04, 0.2, 2 and 8 mg kg –¹), cured tobacco leaves at three spiked levels (0.4, 1 and 10 mg kg –¹) and soil at three spiked levels (0.005, 0.05 and 0.5 mg kg –¹), respectively. The results showed that the half-lives of kresoxim-methyl in green tobacco leaves and soil were 1.2–5.3 days and 6.7–10.4 days, respectively. At harvest, kresoxim-methyl residues in cured tobacco leaves samples collected 21 days after the last application at the recommended dosage were below 1.0 mg kg –¹. These results could help establish appropriate application frequency and harvest intervals in the use of kresoxim-methyl on tobacco plants.