| Triazole fungicides have been widely used in the world.At present,about 84%of triazole fungicides are chiral pesticides.The chemical and physical properties of chiral pesticides are the same in achiral environment,but there are usually differences in biological activity,toxicity and environmental behavior in chiral environment.The biological activity of some chiral pesticides is usually provided by only one enantiomer,while the other enantiomer has no biological activity and even has toxic effects on non-target organisms.These differences may also affect the dissipation rate of chiral pesticides,resulting in one enantiomer being more persistent than the other in natural and agricultural environments.At present,most chiral pesticides are still produced and applied in the form of racemes,which affects the accuracy of pesticide risk assessment and poses a potential threat to human health and environmental safety.Therefore,it is very important to analyze the environmental behavior of chiral pesticides at the enantiomeric level.Triazole chiral fungicides uniconazole and cyproconazole are widely used to treat plant fungal pathogens,prevent crop losses and increase agricultural production.At present,the study on the difference of environmental behavior between uniconazole and cyproconazole from the perspective of enantiomers is still not perfect.In order to comprehensively and accurately assess the risk of uniconazole and cyproconazole,the stereoselectivity behavior of uniconazole and cyproconazole in earthworm-soil microcosm were studied at the enantiomeric level.(1)By using supercritical fluid chromatography-tandem mass spectrometry(SFC-MS/MS),the chiral separation conditions of uniconazole and cyproconazole were studied.the effects of the types of chiral stationary phase,the types and proportions of modifiers,the temperature and flow rate of chromatographic column on the separation were compared.OZ-3 column,20%methanol,column temperature of 30℃ and flow rate of 3.0 mL/min were selected as the best separation conditions of uniconazole enantiomers,and the resolution(RS)was more than 1.5.OZ-3 column,12%methanol,column temperature of 40℃ and flow rate of 3.0 mL/min were selected as the best conditions for the separation of cyproconazole enantiomers,and the resolution(Rs)was>1.5.(2)Based on supercritical fluid chromatography-tandem mass spectrometry(SFC-MS/MS)and QuEChERS method,the method for the determination of uniconazole and cyproconazole residues in earthworm and artificial soil was established,and the feasibility of the method was evaluated by linearity,matrix effect(ME),recovery rate and quantitative limit(LOQ).The linear relationship between the enantiomers of uniconazole was good in the concentration range of 0.1～100 μg/L,and the correlation coefficient(R2)>0.9991.-88.7%<ME<-60.7%,mainly showing strong matrix effect.The average recovery of uniconazole in earthworm and soil samples was 83.3%～111%,RSD was 0.7%～7.4%,and LOQ was 5 ng/g.The enantiomers of cyproconazole had a good linear relationship in the concentration range of 0.1～100 μg/L,and the correlation coefficient(R2)was>0.9981.96.1%<ME<-27.0%,mainly showing strong matrix effect.The recovery rate of cyproconazole was 82.3%～113%,RSD was 0.4%～7.3%,and LOQ was 0.01 ng/g.(3)Based on artificial standard soil and Eisenia foetida model organism,the earthworm-soil microcosm was constructed.The environmental behavior of uniconazole enantiomers in earthwormsoil microcosm was studied.In the process of bioaccumulation,the concentration of uniconazole in earthworm first increased and then decreased,and reached the highest concentration(about 2600 ng/g)on the seventh day of bioaccumulation.The concentrations of S-(+)-uniconazole and R-(-)uniconazole were similar,and the EF value was 0.501～0.511.At the same time,the bioaccumulation factors(BAF)of uniconazole in earthworm was 1.0～2.1,which indicates that earthworm has weak ability to enrichment uniconazole enantiomers and has no stereoselectivity.S-(+)-uniconazole and R-(-)-uniconazole dissipated slowly in soil,and the dissipation half-life was 25.7 days.The EF value of uniconazole was between 0.503 and 0.511,and there was no stereoselectivity in the dissipation of uniconazole enantiomers in artificial soil(p>0.05).The elimination half-lives of S(+)-uniconazole and R-(-)-uniconazole in earthworm were 7.1 and 7.2 day respectively,and the EF value of uniconazole was between 0.48 and 0.51.There was no stereoselectivity in the elimination of uniconazole enantiomers in earthworm(p>0.05).(4)Based on artificial standard soil and Eisenia foetida model organism,the earthworm-soil microcosm was constructed.The environmental behavior of cyproconazole enantiomers in earthworm-soil microcosm was studied.In the process of bioaccumulation,the concentration of cyproconazole in earthworm showed a trend of increasing at first and then decreasing,and reached the highest concentration on the fifth day of bioaccumulation.The concentrations of(2R,3R)-,(2R,3S)-,(2S,3S)-,and(2S,3R)-cyproconazole were 159.5,146.5,226.8 and 258.9,respectively.The EFA and EFB values of cyproconazole ranged from 0.411 to 0.504 and 0.348 to 0.437,respectively.The enantiomers of cyproconazole were stereoselectively bioaccumulated in earthworm(p<0.01),and(2S,3R)-and(2S,3S)-cyproconazole were preferentially bioaccumulated in earthworm.The DF value fluctuated around 0.5,and there was no diastereoselectivity between cyproconazole(p>0.05).(2S,3R)-cyproconazole has the highest concentration in earthworm,and the BAF value of(2S,3R)cyproconazole was the highest,while(2R,3S)-cyproconazole has the lowest concentration.The enantiomers of cyproconazole dissipated slowly in artificial soil.The disspation half-lives of(2R,3R)-,(2R,3S)-,(2S,3S)-,and(2S,3R)-cyproconazole in soil were 20.1,21.0,23.6 and 23.0 days,respectively.The changes of EFA,EFB and DF values of cyproconazole were not significantly different from the initial values,and fluctuated around 0.5(p>0.05).The elimination half-lives of(2R,3R)-,(2R,3S)-,(2S,3S)-,and(2S,3R)-cyproconazole in earthworm were 5.81,6.01,6.01 and 6.01 days,respectively,and the ranges of EFA and EFB of cyproconazole were 0.411～0.41,respectively.(2R,3R)-and(2R,3S)-cyproconazole were preferentially eliminated in earthworm,and the DF value was about 0.5.There was no diastereoselectivity between the enantiomers of cyproconazole. |
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