百菌清及其代谢产物(4-羟基百菌清)在油麦菜及土壤中的残留降解研究

Research on the residue and degradation dynamic of chlorothalonil and its metabolite(4-hydroxy chlorothalonil) in Lactuca sativa and soil

目的建立气相色谱法(gas chromatography,GC)和液相色谱-串联质谱法(liquid chromatography-tandem mass spectrometry,LC-MS/MS)测定油麦菜及土壤中百菌清及4-羟基百菌清残留的方法,同时研究油麦菜及土壤中百菌清及4-羟基百菌清的残留降解规律。方法油麦菜和土壤中的百菌清分别采用乙腈溶液匀浆提取和振荡提取,使用固相萃取柱净化,气相色谱法带电子捕获检测器测定;油麦菜和土壤中的4-羟基百菌清分别采用乙腈溶液匀浆提取和振荡提取,氮吹至近干用甲醇复溶后过0.2μm滤膜净化,进LC-MS/MS测定分析。结果在0.01~5 mg/L范围内,百菌清及4-羟基百菌清均线性良好;在添加量均为0.01~1 mg/kg时,百菌清在油麦菜和土中的添加平均回收率分别为78.5%~79.8%、79.2%~82.4%,相对标准偏差(relative standard deviation,RSD)分别为3.01%~7.21%、5.06%~5.95%。4-羟基百菌清在油麦菜和土中的添加平均回收率分别为96.2%~116.7%、102.1%~113.9%,RSD分别为4.57%~6.22%、2.99%~4.57%。百菌清及4-羟基百菌清在油麦菜及土壤中的消解动态均符合方程C_t=C_(0e)^(-kt):百菌清在油麦菜中的半衰期为1.7 d,在土壤中半衰期为7.5 d,4-羟基百菌清在油麦菜中的半衰期为2.0 d,在土壤中半衰期为7.5 d。结论该方法简单快速,可同时测定百菌清及其代谢物,上述结果可为今后安全、合理、高效使用百菌清提供一定的参考价值。

Objective To establish a method for determination ofchlorothalonil and 4-hydroxy chlorothalonil in Lactuca sativa and soils by gas chromatography （GC） and liquid chromatography-tandem mass spectrometry （LC-MS/MS）, and investigate the degradation dynamic on residue of chlorothalonil and 4-hydroxy chlorothalonil. Methods Pesticide residues were extracted by acetonitrile, and then there were two steps, one for chlorothalonil and the other for 4-hydroxy chlorothalonil. Chlorothalonil was purified by solid phase extraction, and determined by gas chromatography-electronic capture detector （GC-ECD）; 4-hydroxy chlorothalonil was redissolved with methanol, filtered before determination by LC-MS/MS. Results There were good linear relationship for chlorothalonil and 4-hydroxy chlorothalonil in the range of 0.01-5 mg/L. The recoveries of chlorothalonil were 78.5%-79.8% in Lactuca sativa （RSD=3.01%-7.21%） and 79.2%-82.4% in soils （RSD=5.06%-5.95%） at the 3 spiked levels of 0.01, 0.1, 1 mg/kg. The recoveries of 4-hydroxy chlorothalonil were 96.2%-116.7% in Lactuca sativa （RSD= 4.57%-6.22%）, and 102.1%-113.9% in soils （RSD=99%-4.57%）, respectively. The results indicated that the degradation of chlorothalonil and 4-hydroxy chlorothalonil in Lactuca sativa and soil could be described with equation： Ct=Coe-kt. The half-life of chlorothalonil was 1.7 d in Lactuca sativa and 7.5 d in soil, respectively. The half-life of 4-hydroxy chlorothalonil was 2.0 d in Lactuea sativa and 7.5 d in soil, respectively. Conclusion This simple method can be used to determine chlorothalonil and its metabolite simultaneously. It also can provide certain reference value for safely, reasonably and efficiently use of chlorothalonil.