Study On Enantioselective Environmental Behavior Of Chiral Trizole Pesticides

At present, over 25% of used pesticides are chiral. Different enantiomers of chiral pesticides often exhibit different bioactivity, toxicity as well as metabolism behavior in the environment. The study of environmental behavior of chiral pesticides has great importance on the elucidation and evaluation of relevant ecological effect as well as ecological risk of chiral pesticides in environment.In this paper, three triazole pesicides, i.e., triadimefon, triadimenol and diniconazole, were investigated in details related to their chiral separation and enantioselective degration in soil. Following experimental results were conducted:1) Enantiomeric separation of chiral pesticidesEnantiomers of three triazole pesticides, i.e., triadimefon, triadimenol and diniconazole, were successfully separated by using chiral HPLC. Influence of different chiral columns and mobile phase on the separation results was further investigated.2) Determination of optical rotation and absolut configurations of enantiomers of triazole pesticidesIndividual enantiomers of triazole pesticides were prepared by chiral HPLC and their optical rotation activity was further determined using polarimeter. The absolute configurations of triadimefon and diniconzaole enantiomers were determined on the basis of reported literature. Moreover, the absolute configurations of the four triadimenol stereoisomers were deduced via the reductive experiment of triadimefon to triadimenol.3) Chiral stability of triazole pesticides in organic solvents and waterChiral stability of three triazole pesticides in different organic solvents and buffer solutions was studied. Significant enantiomerization of triadimefon enantiomers was observed in methanol, ethanol and water. Triadimenol and diniconazole were showed configurationally stable in organic solvents and water. Influence of temperature and pH value on the enantiomerization of triadimefon enantiomers was further investigated.5) Enantioselective degradation of triadimefon and diniconazole in soilsEnantioselective determinantion of triadimefon, triadimenol, and diniconazole in soils was accomplished by Matrix Solid-phase Dispersion (MSPD) extraction in combination with chiral and achiral HPLC. On this basis, enantioselective degradation of triadimefon and diniconazole was investigaed in details. Diniconazole was showed to degrade very slowly in Tianjin alkaline soil and no obvious enantioselectivity was observed. As for triadimefon, the degradation was fast with half-lives of and in Baoding alkaline and Hubei acidic soils, respectively. The degradation of triadimefon was faster in Baoding soil than in Hubei soil. Obvious enantioselectivity was observed in Hubei soil with S-(+)-triadimefon faster degraded than R-(-)-triadimefon. Furthermore, the incubation of enantiopure triadimefon enantiomers in the two soils showed significant enantiomerization took place along with the degradation. At last, triadimenol-B was identified as the main degradation product of triadimefon degradation in the two soils. Further chial analysis showed different enantiomer composition of the formed triadimenol when racemic triadimefon and enantiopure enantiomers were separately incubated in the two soils.