黄瓜和土壤中吡唑醚菌酯和霜脲氰同步检测及其降解分析

采用QuEChERS-液相色谱-串联质谱法，建立黄瓜及土壤中吡唑醚菌酯和霜脲氰同步检测方法，研究吡唑醚菌酯·霜脲氰水分散粒剂在黄瓜和土壤中的残留变化及消解动态，旨在评估联合农药的安全性。样品经乙腈提取，N-丙基乙二胺吸附剂和十八烷基键合硅胶吸附剂净化，质谱多反应监测模式扫描。在50～800?μg/L之间具有良好的线性关系，r值均大于0.996?1，3?个质量浓度添加水平下2?种农药在黄瓜和土壤中的平均回收率为70.45%～107.08%，定量限均为0.050?mg/kg。两年三地的田间实验消解动态表明：以1.5?倍高推荐剂量下，吡唑醚菌酯和霜脲氰分别于黄瓜上施药1、7?d后，土壤上施药7、1?d后残留量小于定量限；当该制剂以推荐剂量在黄瓜上施药3?次，施药间隔7?d时，吡唑醚菌酯和霜脲氰在黄瓜中的最高残留量分别为0.090?mg/kg和0.060?mg/kg，远低于我国规定的最大残留限量0.5?mg/kg，推荐采收安全间隔期为3?d。

Simultaneous Detection and Degradation of Pyraclostrobin and Cymoxanil in Cucumber and Soil

In this paper, a method for the simultaneous detection of pyraclostrobin and cymoxanil in cucumber and soil was developed using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The degradation kinetics and the final residue of pyraclostrobin-cymoxanil water dispersible granule in cucumber and soil were studied, aiming to evaluate the safety of this pesticide combination. Samples were extracted with acetonitrile and the extract was cleaned up with primary secondary amine (PSA) and C18 before being analyzed by mass spectrometry in the multiple-reaction monitoring (MRM) mode. There was a good linear relationship within the concentration range of 50–800 μg/L with correlation coefficients (R2) greater than 0.996 1. The average recoveries of two pesticides in cucumber and soil were 70.45%–107.08% at three spiked concentrations. The limit of quantification (LOQ) was 0.050 mg/kg for both. Two-year field experiments at three different locations showed that the residual concentrations of pyraclostrobin and cymoxanil were lower than the LOQ after 1 and 7 d, and 7 and 1 d after being applied at the high recommended 1.5-fold dose to cucumber and soil, respectively. When applied at the recommended dose 3 times to cucumber with a 7 d interval between each dose, the maximum residual concentrations of pyraclostrobin and cymoxanil were 0.090 and 0.060 mg/kg, respectively, which were lower than China’s maximum residue limits (MRL) for pyraclostrobin and cymoxanil in cucumber (0.5 mg/kg). The recommended safe pre-harvest interval was 3 d.