有机磷农药辛硫磷的醇解动力学及机理研究

辛硫磷,又名O,O-二乙基-O-（苯乙腈酮肟）硫代磷酸酯,是一种低毒、广谱、高效的有机磷杀虫剂,对害虫有强烈的触杀作用。采用气相色谱-火焰光度检测器（GC-FPD）研究了不同温度下辛硫磷甲醇溶液的稳定性。结果表明,辛硫磷在0～4℃下保存280d后损耗不足1%,该温度适合长时间贮存辛硫磷甲醇储备液;40℃下保存160d后,损耗达8%,其动力学行为符合一级动力学方程式：lnC]/C0]=-6×10-4t·d-1,半衰期为1155.2d。损耗部分的辛硫磷通过气相色谱-电子电离质谱（GC-EI-MS）分析,推断可能发生醇解转化为O-甲基-O,O-二乙基硫代磷酸酯,为有机磷农药的醇解提供了科学依据。

Alcoholysis Kinetics and Mechanisms Study of Organophosphorus Pesticides Phoxim

The alcoholysis kinetics and mechanisms of organophosphorus pesticide phoxim in methanol solution under different temperature were investigated in our study.Experimental results showed that phoxim was quite stable in methanol solution with less than 1% depletion after 280 days at 0～4 ℃,which suggested that 0～4 ℃ suited for the preservation of phoxim methanol solutions.However,when stored at 40 ℃ for 160 days,the depletion reached 8% and the alcoholysis reaction followed the first-order kinetics equation lnC]/C0] =-6×10-4 t·d-1 with a half-life of 1 155.2 days.Subsequently,a method using GC-MS was developed to isolate and identify the alcoholysis product.The product was identified and characterized as O-methyl-O,O-biethyl thiophosphate.And from the alcoholysis product,the probable alcoholysis pathway for phoxim was proposed that phoxim alcoholized largely via methoxy acting as nucleophile to give rise to O-methyl-O,O-biethyl thiophosphate.