腈菌唑在番茄果实中的立体选择性降解

为明确田间条件下手性杀菌剂腈菌唑对映体在番茄果实中的降解规律，采用Lux Cellulose-1手性色谱柱及超高效液相色谱-串联三重四极杆质谱 (UPLC-MS/MS) 分析方法，研究了腈菌唑对映体的分离及其在番茄果实中的选择性降解。样品经乙腈提取，采用QuEChERS 方法净化。分析方法验证结果表明:在0.000 5~0.05 mg/L线性范围内，腈菌唑对映体的峰面积与其浓度间呈良好的线性关系，R2均大于0.99；在0.005、0.05和0.25 mg/kg 3个添加水平下，腈菌唑对映体在番茄中的平均回收率在92%~96%之间，相对标准偏差 (RSD) 在1.0%~3.0%之间。降解试验结果显示:腈菌唑对映体在番茄果实中的降解规律符合一级反应动力学方程，其降解半衰期在2.77~4.08 d之间；腈菌唑对映体在番茄果实中的降解具有明显选择性，随时间延长，其对映体分数 (F_E) 值由最初的0.47下降为0.24，其中S-(+)-腈菌唑优先降解，从而导致R-(–)-腈菌唑的相对富集。本研究从对映体的角度评价了腈菌唑在番茄中的降解，可为手性农药对映体的环境行为研究提供基础数据。

Enantioselective degradation of fungicide myclobutanil in tomato

To investigate the degradation of enantiomers of myclobutanil in tomato (Lycopersicon esculentum Mill.) fruits under field conditions, the separation of myclobutanil enantiomers and the enantioselective degradation in toamto were studied using a chiral Lux Cellulose-1 column separation and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were extracted by acetonitrile and purified with QuEChERS. The method showed reliable performances in linearity, recovery and precision. The correlation coefficient of calibration curves were over 0.99 in the range of 0.000 5 to 0.05 mg/L, the average recoveries of myclobutanil enantiomers in tomato varied from 92% to 96% with the relative standard deviation (RSD) ranging from 1.0% to 3.0% at 0.005, 0.05 and 0.25 mg/kg spiked level. Results of degradation trials indicated that the degradation of enantiomers of myclobutanil in tomato fruits followed to the first-order reaction kinetic equation. And the half-lives of myclobutanil enantiomers ranged from 2.77 d to 4.08 d. The degradation of myclobutanil enantiomers in tomato fruit exhibted significant selectivity. The enantiomer fraction (F_E) values decreased with time from 0.47 to the minimum of 0.24. S-(+)-Myclobutanil was more susceptible to degradation in tomato, which resulted in the relative enrichment of R-(–)-myclobutanil. The degradation of myclobutanil in tomato was evaluated from the perspective of enantiomers, and the results of this study would provide the basic data support for the risk assessment of myclobutanil in agricultural products.