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Wu M.,Shanghai JiaoTong University | Xiao J.,Key Laboratory of Urban Agriculture South | Cai J.,Agrochemical and Chemical Co. | Yao J.,Agrochemical and Chemical Co. | And 3 more authors.
Fresenius Environmental Bulletin | Year: 2010

As a new neonicotinoid insecticide, imidaclothiz has been recently used in tea-fields in China. In this paper, the degradation dynamics of imidaclothiz in fresh tea, dried tea and soil were studied. Imidaclothiz residue was extracted with acetonitrile and cleaned up by a modified ENVI™-Carb method. HPLC with UV detection was employed to determine concentrations of imidaclothiz residues. The accuracy and precision of this method were validated. Two kinds of dosages of wettable powder concentrate with 10% imidaclothiz were applied in field, the recommended dose (450 g hm-2) and the double of the recommended dose (900 g hm-2). In the recommended dose group, the degradation dynamics coincided with the following equations: Ct = 2.721e -0.224t, Ct = 0.516e-0.138t, and Ct = 0.714e 0.096t for fresh tea, dried tea and soil, respectively. In the double dose group, the dynamics equations were Ct = 5.225e0.159t, Ct = 0.938e-0.145t, and Ct = 2.662e-0.038t, respectively. The final residue level was lower than the tentative maximum residue limit (MRL) of imidaclothiz on fresh tea, with a harvest interval of 45 days. © by PSP.

Wu M.,Shanghai JiaoTong University | Cai J.,Agrochemical and Chemical Co. | Yao J.,Agrochemical and Chemical Co. | Dai B.,Agrochemical and Chemical Co. | Lu Y.,Shanghai JiaoTong University
Bulletin of Environmental Contamination and Toxicology | Year: 2010

The HPLC method for determination of imidaclothiz residue in cabbage and soil was developed, and its degradation and final residue were studied. The mean accuracies of the analytical method were 92.0-93.0% in soil and 88-93% in cabbage. The precision in cabbage ranged from 2.2% to 5.6%, and in soil from 2.0% to 5.0%. The minimum detectable amount of imidacothiz was 1 × 10 -10g. The minimum detectable concentration was 0.0075 mg kg -1 in cabbage and 0.003 mg kg -1 in soil. The results showed that imidaclothiz degradation in soil and cabbage coincided with C = 0.0427e -0.0923t, C = 0.739e -0.279t. The half-lives were about 3.1 days in soil and 2.2 days in cabbage. © 2010 Springer Science+Business Media, LLC.

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