Optimization Of High Performance Micro-fluidic Electrochromatography And Its Application In Food Safety

Pressurized capillary electrochromatography(pressurized capillary electrochromatography, p CEC), can be also called high performance micro-fluidic electrochromatography, is a newly developed separation technique. It integrates the advantages of capillary liquid chromatography(c LC) and capillary ectrophoresis(CE) with dual separation mechanism. Fully automatic p CEC consists of the following modules: a solvent delivery module, a UV/Vis detector, a controller, a micro fluidic control module, an auto sampler, a high voltage power supply, and solvent tray. In addition to UV/Vis detector, it can also be coupled to other detectors, such as micro fluidic laser induce fluorescencedetector,(μLIF), micro fluidic evaporative light scattering detector(μELSD), micro fluidic electrochemical detector(μECD), and nano electrosprayionization mass spectrometry(nano ESI-MS).This thesis is divided into seven chapters:The first chaper introduces the background and significance of this project, including the principles, applications and apparatus of CE, CEC and p CEC. Summarize the optimization of p CEC system and its application in food safety.The second chapter of the thesis is mainly focuses on the optimization and evaluation of p CEC instrument. 1. A thermostat was developed for p CEC and the performance in terms of retention time, peak area, column efficiency and trailing factor was tested at different temperature(4℃, 10℃, 20℃, 30℃, 40℃) and under different mode(μHPLC, p CEC). The thermostat with cooling capacity can be used to achieve accurate temperature control as well as minimize the impact of Joule heat. The temperature control can be used as a measure in actual applications to achieve better separation. 2. Evaluated the connector used for holding the electrode by V comparing the difference between 1/16 ″ cross and 1/32 ″ cross connectors. 3. Investigated feasibility of utilizing the nano injector for p CEC system, only to split the mobile phase, but without splitting the sample to achieve quantitative injection. By comparing the dead volume and the electrode reaction of several different methods(micro tee, stainless steel union, titanium alloy union), the titanium alloy uion was selected as the connector, which may lay a solid foundation for quantitative injection in p CEC.The third chapter of the thesis is to study the coupling of p CEC with MS. Coupling p CEC with MS, applying positive voltage on the cross, zero voltage on the end of the capillary colomn. Comparing the electrode reaction of several different access methods, the final choice is the decoupler. In addition, optimize the pipeline between six port vavle injector and splitting cross. Compare the material, diameter, length of the piplin e, the finial choice is the PEEK pipline(20 cm length, 100 μm i.d.).The forth chapter of the thesis isto combine μCCD with p CEC, testing the limit of detection, compared with that of UV/VIS detection, which lays the foundation for the cell design of p CEC-μCCD.The fifth chapter is concerned with the analysis of aflatoxin in foods by using p CEC-μLIF. The mobile phase was 45% methanol(0.05% FA, p H 3.2), the splitting ratio was 1:300, the separation voltage was 15 k V. Four aflatoxin(B1, B2, G1, G2) were baseline separated in the mode of isocratic p CEC elution. The LOD of each aflatoxin(S/N=3) were 0.02、0.016、0.008、0.01 μg/m L. The recoveries of foods were 90.0%~112.0%, with RSD ranged 0.5%~1.9%.The sixth chapter concerned with the method development for parabens and antioxidants analysis in foods by p CEC-UV/Vis. The mobile phase was acetonitrile/water(0.05% formic acid, p H3.0), the splitting ratio was 1:300, the separation voltage was 15 k V. Parabens and antioxidants(PG, THBP, TBHQ, EP, PP, BHA, OG, BHT) were baseline separated in the mode of gradient elution. The LOQ of each sample were 0.8、1.0、5.0、1.7、2.5、3.1、1.6、8.3 μg/m L. The spiked recoveries were 90.7%~101.1%, with RSD ranged 0.1%~1.9%.The seventh chapter summarized the whole thesis and looked into the the prospect of this innovitave technology.