| Due to its characters of high effectiveness, low toxicity and broad spectrum, deltamethrin has been widely used in pest insect prevention for Chinese herbal medicine. In this paper, the residue determination and degradation of deltamethrin in soil and Chinese herbal medicine were studied, in order to establish the MRL standard for safe deltamethrin using in Chinese herbal medicine planting. In this article, Polygonum Capitatum Buch was chosen to be our study object. The sample was extracted by ultrasonic wave assisted method and was purified by Florisil. Residue of deltamethrin in Polygonum Capitatum Buch and soil was analyzed and studied by GC-ECD with pre-column. Comparison was made within several different ways of sample extraction,different eluents and different sorbents to find out their influence on the test result respectively. The result is that: ultrasonic wave assisted method is better for the sample extraction and the mixture of petroleum ether-ethylacetate (9:1) and purified by the Florisil is the most satisfactory match of eluent and sorbent. The average recoveries of the three spiked levels of deltamethrin was 80.6-99.3% in Polygonum Capitatum Buch; the Coefficient of Variation (CV) was 3.4-13.1%, the limit of quantification (LOQ) was 0.01 mg/kg; and the limit of detection (LOD) was 4.7×10-3 ng. This result can obviously prove that the accuracy, exactitude and sensitivity of this method meet the requirements of pesticide residue analysis.The results of detection showed that the degradation half-lives of deltamethrin were 2.1-2.6 d in Polygonum Capitatum Buch and 3.3-3.4 d in soil respectively. The final residues of deltamethrin in Polygonum Capitatum Buch and soil were less than 0.01 mg/kg. |
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