Development Of A Pressure Assisted-valve Injection Capillary Electrophoresis With High-precision Quantitative Capability And Its Application In The Analysis Of Food And Health Care Products

Capillary electrophoresis（CE）has been widely used in various fieldssuch as pharmaceutical, environmental, biotechnology and chemicalanalysis since it was firstly developed in1980s. However, this technique isnot perfect，there are still some drawbacks, especially those associated withsample introduction. The lack of a reliable mode of sample introductionhampers the application of CE in quantitative analysis. We constructed apressure assisted-capillary electrophoresis system with high accuracy andhigh precision, and optimized the experimental conditions, obtained thegood results on the analysis of real samples by using this system. Besides,we combined this system with micellar electokinetic capillarychromatography (MEKC) successfully, which made the system not only have the advantage of MEKC in the separation of neutral substances，butalso with superior quantitative capability. This dissertation is divided intofour chapters as follows:In Chapter1, we briefly introduced the background and significance of theproject, mainly focused on CE and MEKC. The development andapplication of CE and MEKC in many fields were reviewed. The overviewof injection technology of traditional CE also provided, with thedescription of problems and difficulties in current injection technology.In Chapter2, We constructed a pressure assisted-capillaryelectrophoresis system with high accuracy and high precision, optimizedthe hardware of the system. Pressure assisted-capillary electrophoresissystem with high accuracy and high precision was set up. A10nL4-portinjecction valve and a micro flow syringe pump were introduced into thetraditional CE system, in which the4-port injection valve was isolatedfrom the electrical field by an electrical decoupler. Separation speed,column efficiency, quantitative reproducibility, consecutive injectionreproducibility and separation selectivity of the system were investigated.Results showed that the qCE system was stable, reliable, and greatlyenhanced the performance of capillary electrophoresis in terms ofquantitative and consecutive operation, Reproducibilities lower than2% (RSD) for both retention time and peak area were achieved.Chapter3focused on the application of pressure assisted-capillaryelectrophoresis system with high accuracy and high precision indetermining the content of cordycepin, adenine, adenosine, uridine, uracilin real sample. Establishment of experimental conditions for cordycepin,adenine, adenosine, uridine, uracil: the type of buffer, buffer concentration,buffer pH value and the electrophoresis voltage were studied. The bestexperimental conditions for the CE separation were40mM of borax(pH9.0) buffer as a background electrolyte with-15kV operating voltage.Under this condition, baseline separation of five kinds of nucleoside andbase was achieved. The effectiveness of the system was demonstratedby the quantitative analysis of cordycepin, adenine, adenosine, uridine,uracil in real samples, such as cordyceps powder and cordyceps capsules.In Chapter4, we used the system in the MEKC mode successfully,which made the system not only have the advantage of MEKC in theseparation of neutral substances，but also with superior quantitativecapability. Its performance was evaluated and compared with theconventional injection method, then, we use the system for a quantitativedetermination of five parabens in vinegar. Relative standard deviations(RSDs) in terms of migration time and peak area of benzoic acid, benzene, toluene and DMSO as measured by using this nano-valve quantitativemethod and compared to those by using the electrokinetic method andhydrodynamic method. The results showed that injection accuracy andprecision of the quantitative nano-valve method were superior to those oftraditional electrokinetic method and hydrodynamic methods. Thechromatographic conditions for four parabens: SDS concentration, bufferconcentration, buffer pH value were optimized. The best conditions wereestablished as15mM of borax buffer with100mM SDS (pH9.0) as abackground electrolytes with-15kV operating voltage. Under thecondition, baseline separation of the four parabens was achieved.We introduced a10nL4-port injecction valve and a micro flowsyringe pump into the built-up system. The former solve the problem ofthe system in column efficiency, and the introduction of the latter can beflexible to improve the analysis speed, optimize separation selectivity ofthe system. After optimization and evaluation of the system, we used it forquantitative analysis in real samples, which confirmed the superiority of itsquantitative capability.