Residue analysis and dissipation dynamics of chlorpyrifos in cotton and soil

【Objective】Safety assessment of chlorpyrifos in cotton and soil was conducted to provide important scientific references for the rational use of pesticides in cotton. 【Method 】The quantitative analysis of chlorpyrifos was done by GC-FPD and the established pretreatment method of chlorpyrifos in cottonseed, leaf of cotton and soil. Dissipation dynamics and residues of chlorpyrifos in cottonseed, leaf of cotton and soil were studied through residue experiments in two years(2009,2010) in two places(Henan, Jiangsu). 【Result】The average fortified recoveries in cottonseed, leaf of cotton and soil were 73.50%-105.66%,with the relative standard deviation of 3.25%-9.89%. The limit of detection of the analytical method was 2.5×10-11g, and the lowest limit of quantification was 0.013, 0.012 and 0.005 mg/kg in cottonseed, leaf of cotton and soil, respectively. The dissipation half-lives of chlorpyrifos in cotton leaf and soil were 3.0-4.0 d and 6.2-8.9 d, respectively. The final residues of chlorpyrifos in cottonseeds were all ≤0.026 mg/kg in different sampling intervals and application frequencies. 【Conclusion】Chlorpyrifos is easily dissipated with low residues in cottonseed, so it can be safely used in cotton crops when the dosage is below 562.5 ga.i./ha, by spraying 3 times with the interval of 21 d.