Wide Dry Spirit Hymexazol And Metalaxyl In Chinese Herbal Medicines Head To Spend The Residue Dynamics Of Polygonum And Soil,

Guangkuling, a mixture of hymexazol and metalaxyl serving as active ingredients, is developed by Center for Research and Development of Fine Chemicals Guizhou University. As a high performance fungicide associated with low toxicity, Guangkuling has been widely used for controlling many Chinese herbal medicinal diseases, such as damping-off, Blight, Wilt and so on. In order to assess the safety days and support scientific evidence of Guankuling applied on Polygonum Capitatum Buch. Hymexazol and metalaxyl residues in Polygonum Capitatum Buch and soil residual dynamics were studied in the present research respectively.A method was developed for the determination of hymexazol and metalaxyl residues in Polygonum Capitatum Buch and soil respectively. Residues of hymexazol in Polygonum Capitatum Buch and soil were analyzed and studied by GC-FPD with pre-colu'mn derivatization technology. The samples were extracted by acetone, derivatizated to diethyl thiophosphate and cleaned up on a column of Florisil. Hymexazol residues were determined by external standard method. The limit of detection (LOD) was 1.02×10^-10 g. The limit of quantification (LOQ) was 0.01 mg/kg. Average recoveries at 0.01～1.0 mg/kg level were in the range from 81.4% to 106.1% with a C.V. of 1.9～9.4%. HPLC-UV was developed to determine metalaxyl residues in Polygonum Capitatum Buch and soil. Samples were extracted by methanol, cleaned up by dichloromethane, in addition, samples of Polygonum Capitatum Buch were cleaned up on a column of neutral alumina. The content of metalaxyl was determined by external standard method. The limit of detection (LOD) was 3.58×10^-10 g. The limit of quantification (LOQ) was 0.05 mg/kg. Average recoveries at levels of 0.05～2.0 mg/kg were in the range from82.5 to 104.4% with a C.V. of 1.7～5.0%. The results showed that the method was suitable for determining hymexazol and metalaxyl in Polygonum Capitatum Buch and soil respectively.The results of detection showed that the degradation half-lives of hymexazol were 2.8～3.0 d in Polygonum Capitatum Buch and 6.0～6.2 d in soil respectively. The final residues of hymexazol in Polygonum Capitatum Buch were less than 0.034 mg/kg, which was lower than 0.5 mg/kg of Japanese Maximum Residue Limit on rice. Half-life of metalaxyl in Polygonum Capitatum Buch was 6.7～7.3 d, whereas in soil it was 12.6～13.9 d. The final residues of metalaxyl were less than 0.267 mg/kg in Polygonum Capitatum Buch. The residue level of metalaxyl in Polygonum Capitatum Buch was lower than 0.5 mg/kg, the Maximum Residue Limit on Vegetables in China. Therefore, 11.25～22.50 g.a.i/ha appears to be a safe recommended dose on Polygonum Capitatum Buch in Guiyang area.