Study On Method Development For The Determination Of Drug Residues In Food And Water By Online Preconcentration Capillary Electrophoresis

Capillary electrophoresis(CE)is a type of liquid phase separation technology in which a capillary was used as a separation channel and a high voltage direct current electric field as a driving force.It has advantages of easy operation,low cost,small sample consumption and high separation efficiency.It is one of the important technologies in food and environment analysis.However,due to the small amount of sample injection and the short optical path of detection,it is usually necessary to use enrichment methods to improve the sensitivity of detection to satisfy the requirements of analysis.In this paper,the application of CE technology in food and wateranalysis was investigated.Different separation conditions are selected according to the characteristics of different analytes combined with appropriate enrichment methods to improve the detection sensitivity.Main contents are as follows:In Chapter 1,the principles of capillary electrophoresis are discussed.The separation mode,sample injection method and detection technology of capillary electrophoresis are introduced.At the same time,the enrichment method and principle of capillary electrophoresis and its application in food and environmental water analysis are introduced.In Chapter 2,the determination of clonidine(CLO)and cyproheptadine(CYP)in animal-derived food was developed by sweeping-micellar electrokinetic chromatography(sweeping-MEKC).During the experiment,the factors affecting the sweeping were optimized,and the optimal conditions obtained were buffer solution of 20 m M NaH₂PO₄,90 m M SDS and 20%(V/V)ACN at pH 2.4,sample matrix of 70 m M NaH₂PO₄.Sample was injected by pressure injection at 0.7 psi for 100 s,the voltage was-20 k V.The detection wavelength is 210 nm.Under the optimal conditions,the LODs of CLO and CYP were 0.023 and 0.031?g/m L,which showed a 50-fold increase in sensitivity compared with the CZE method.The recoveries of chicken and pork samples were87.5%?90.1%,and the RSDs were less than 3.11%.In Chapter 3,a method for the determination of plant growth hormones4-chlorophenoxyacetic acid(4-CA)and 3-indoleacetic acid(IAA)in bean sprouts was developed by field amplified sample injection-capillary electrophoresis(FASI-CE).The factors affecting the separation of FASI and CZE were investigated,and the optimal experimental conditions were obtained.The buffer solution was 20 m M borax containing10%(V/V)MeOH at pH 10.0,and the separation voltage was 20 k V.The conditions of electrokinetic injection were as follows:a water plug was injected at 0.5 psi for 5 s before sample injection,sample injection voltage was-10 k V,and the injection time was60 s.30%(V/V)MeOH was used to dissolve the sample.The detection wavelength is208 nm.Under the optimal conditions,the LODs of 4-CA and IAA were 0.0042 and0.0051?g/m L,which was about 300 times more sensitive than the CZE method.The recoveries of the three bean sprout samples were 93.5%?114.3%,and the RSDs were less than 5.28%.In Chapter 4,a large-volume sample stacking-capillary electrophoresis(LVSS-CE)method was developed for the determination of the herbicides picloram and aminopyralid in water.The influencing factors of large-volume sample stacking were investigated,and the optimal conditions obtained were:Sample was injected by pressure injection at 1.5psi for 80 s,application of reverse voltage at-10 k V for 4.5 min.Separation was performed in a 30 m M borax(pH 9.2)solution containing 10%(V/V)ACN with a separation voltage of 20 k V and a detection wavelength of 224 nm.Under optimal conditions,the LODs of the two herbicides were 0.032 and 0.028?g/m L,respectively,which had satisfied the testing requirements of the United States Environmental Protection Agency(US-EPA).The recoveries of the actual samples of drinking water and tap water were 91.6%?104.2%,and the RSDs were less than 3.14%.In Chapter 5,a method for the determination of antidepressant flupentixol(FLU)and melitracen(MEL)in water was developed by sweeping-micellar electrokinetic chromatography(sweeping-MEKC).The factors affecting the sweeping were optimized,and the optimal separation and detection conditions were obtained.Buffer solution was30 m M NaH₂PO₄ containing 50 m M SDS and 30%ACN(V/V)at pH 2.3,and the sample was prepared in 60 m M NaH₂PO₄.Sample injection was at 0.5 psi for 250 s,the separation voltage was-20 k V.The detection wavelength was 230 nm.Under the optimal conditions,the LODs of FLU and MEL were 0.023 and 0.037?g/m L,and the separation could be completed within 8 min.In four water samples(drinking water,tap water,lake water,sea water),the recoveries were 72.1%?98.5%,and the RSDs were less than3.61%.