Chiral Separation And On-line Preconcentration Of Four Chiral Herbicides By Capillary Electrophoresis

The pesticides are produced massively and used widely in our country and about40%with chiral structure. In recent years, with the increasing in production and consumption of chiral pesticides, the level of chiral pesticides residue in environment, food and biology body increased gradually. It is well known that, the enantiomers of pesticides have same physical and chemical characteristics, although have difference in physiological and biochemical characteristics. So the evaluation of environmental safety about chiral pesticides should be conducted on enantiomer level. To establish one efficient and sensitive method to separate the enantiomers of chiral pesticides is the basis of the evaluation of environmental safety about chiral pesticides. To date, capillary electrophoresis is one important method to analys chiral pesticide, except for High performance liquid chromatography and Gas chromatography.Recently, capillary electrophoresis(CE) developed rapidly as one kind of chromatographic technique. Under the force of electric field, the sample separate in the capillary due to the difference of charge-mass ratio. Capillary electrophoresis(CE) is widely used in the field of clinical medicine, agricultural, food, environment, biological and chemical. The advantage of CE is high efficiency, low sample consumption, easy operation and so on. The disadvantage of CE is the low-sensitivity, and on-line preconcentration is an effective means to solve the problem.In our study, chiral separation and on-line preconcentration of four chiral pesticides, including Phenoxyalkanoic acids and Azoles, by capillary zone electrophoresis was conducted. Details are as following:(1) chiral separation and on-line preconcentration of cloprop, dichlorprop and fenoprop by capillary electrophoresis is conducted. The condition of background electrolyte(BGE) is optimized, including the concentration of γ-CD, the concentration of SDS, phosphate concentration and organic modifier. BGE:30mM γ-CD,50mM SDS and5%(v/v) isopropyl alcohol in75mM phoshate buffer was the optimal condition to separate the enantiomers of dichlorprop, fenoprop and cloprop respectively and the values of resolution of dichlorprop, fenoprop and cloprop are2.20,5.20and1.90respectively.Two on-line concentration techniques, stacking and sweeping, are used to enhance the detection sensitivity of CZE system. The stacking-CZE enhanced the detection sensitivity of three phenoxyalkanoic herbicides76-to79-fold and sweeping-CZE enhanced them9-to155-fold. In addition, in order to apply the method to practical use,1.5mg/L mixture sample of dichlorprop, fenoprop and cloprop spiked in tap water was successfully detected and separated by stacking-CZE method.(2) Chiral separation and on-line preconcentration of imazalil by capillary electrophoresis is conducted. The condition of chiral separation is optimized, including the concentration of P-CD, organic modifier, the concentration of NaH2PO4, the concentration of NH4H2PO4and running voltage. BGE:5mM β-CD,75mM NaH2PO4,5mM NH4H2PO4and2.5%(v/v) isopropyl alcohol with running voltage20KV was the optimal condition to separate the enantiomers of imazalil. And the the values of resolution of imazalil is3.0. One on-line concentration techniques, stacking, is used to enhance the detection sensitivity of CZE system The stacking-CZE enhanced the detection sensitivity of imazalil91-to92-fold.