手性三唑酮在3种叶类蔬菜中的立体选择性降解及残留

Stereoselective Degradation and Final Residue of Chiral Triazolone in Three Leafy Vegetables

[目的]明确手性三唑酮在3种叶类蔬菜中的立体选择性降解及残留规律。[方法]通过田间小区试验和超高效液相色谱串联质谱(UPLC-MS/MS)分析技术,研究手性三唑酮在菜心、油麦菜和苋菜中的立体选择性降解行为及最终残留情况。[结果]三唑酮在3种叶类蔬菜中的降解均符合一级动力学规律(r≥0.860),在油麦菜中存在显著的立体选择性降解行为,R-(-)-三唑酮被优先降解,导致S-(+)-三唑酮的富集,半衰期分别为0.8、1.7 d,ES值为-0.3275;而在菜心和苋菜中的立体选择性降解不明显,EF值在0.5~0.6之间,ES绝对值<0.05,S-(+)-三唑酮和R-(-)-三唑酮在菜心中的半衰期均为1.3 d,在苋菜中则分别为3.2、3.3 d。最终残留试验结果表明:施药7 d后,3种叶类蔬菜中S-(+)-三唑酮和R-(-)-三唑酮的降解率均超过96.0%;施药10 d后,菜心和油麦菜中总三唑酮含量均≤0.033 mg/kg,而苋菜中总三唑酮含量为0.048~0.088 mg/kg。[结论]手性三唑酮在不同叶类蔬菜品种中的立体选择性降解存在显著差异,这种差异主要受叶类蔬菜本身酶体系的影响;在菜心、油麦菜和苋菜上喷施20%三唑酮外消旋乳油,按637.5、956.3 g a.i./hm^2的剂量施药1次,采收间隔期为10 d,手性三唑酮在3种叶类蔬菜中的总残留量均低于0.10 mg/kg。

[Aims] In order to determine the stereoselective degradation and terminal residue of chiraltriazolone in three leafy vegetables. [Methods] Field experiments was conducted and UPLC-MS/MS was carried out to study degradation behavior and residue of chiral triazolone in flowering cabbage, leaf lettuce and amaranth. [Results] The dissipation of triazolone enantiomers in three leafy vegetables followed the first-order kinetics(r≥0.860). The degradation rate of R-(-)-triadimefon was faster than S-(+)-triadimefon in leaf lettuce, which had the half-lives of 0.8 and 1.7 d,respectively, and the ES value was-0.3275, indicated that stereoselective degradation in leaf lettuce was significantly.But stereoselective degradation in flowering cabbage and amaranth was unobvious, as the EF values ranged from 0.5 to0.6 and absolute values of ES<0.05. Half-lives of S-(+)-triazolone and R-(-)-triazolone in the flowering cabbage were both 1.3 d, and in amaranth they were 3.2 and 3.3 d, respectively. Final residue results showed that the degradation rates of S-(+)-triazolone and R-(-)-triazolone in three leafy vegetables were more than 96.0% after 7 d application;terminal residues of triazolone both in flowering cabbage and leaf lettuce were ≤0.033 mg/kg, while they were 0.048-0.088 mg/kg in amaranth after 10 d application. [Conclusions] The stereoselective degradation behavior of chiral triazolone in different leafy vegetable was significantly different, which mainly affected by the enzyme system of leafy vegetable.As triazolone 20% racemic cream were sprayed at the doses of 637.5, 956.3 g a.i./ha for one time, with harvest interval was 10 d, the residues of chiral triazolone in flowering cabbage, leaf lettuce and amaranth were less than 0.10 mg/kg.