Optimization Of Pressurized Capillary Electrochromatography System And Its Application In Food Additives

Pressurized capillary electrochromatography (pCEC) is a highlyefficient micro-separation technology, which has developed rapidly inrecent years. It combines the advantages of high performance liquidchromatography (HPLC) and capillary electrophoresis (CE), with " threeseparation modes in one instrument " function (capillaryelectrochromatography, capillary electrophoresis, capillary liquidchromatography), and characteristics of high column efficiency, highresolution, high selectivity with fast separation speed, Its separationchannel is miniaturized, and therefore, it is economical andenvironmentally friendly. Due to the double separation mechanism, theselectivity and resolution have been significantly improved compared withconventional high performance liquid chromatography (HPLC). It hasgreat potential in the study of complex samples in chemical and biologicalsystems.This thesis is divided into five chapters as follows:The first part briefly introduces the background and significance ofthis project, including the principles and applications of pCEC, the ideasand meaning of the optimization of pCEC system, application status andthe research progress of analytical methods in vitamins and so on.The second part concerns mainly the optimization of the existingpCEC system to improve its accuracy and precision, and the use ofautosampler. Since the sample in the current pCEC system is manuallyinjected, it affects the of the experiments to a certain extent and also limitsthe use of pCEC. In this experiment, Arcus5autosampler was coupled with pCEC and capillary liquid chromatography (cLC), Then, using amicro injection valve (10nL), by changing the splitting mode, in which wejust split the mobile phase without splitting the sample so that the10nLsample completely goes into the capillary column. Through theoptimization of connecting tubing, and the position of applied voltage,ultimately, we achieved accurate quantification, and to some extent, alsoimproved the precision of analysis.The third part focuses mainly on the application of pCEC analysis offour fat-soluble vitamins and vitamin tablets in food safety. Fat-solublevitamins were ultrasonically extracted with methanol, the separations wereperformed on a reversed-phase C18capillary column with a certaindetection wavelength-time program. The mobile phase was95%（V/V）methanol containing0.05%TFA (pH3.3) at a pump flow rate of0.2mL/min with the separation voltage of-15kV. Four fat-soluble vitamins(vitamin A, vitamin D3, vitamin E, vitamin K3) were baseline separatedwithin5min in isocratic pCEC mode. The detection limits of each vitamin(S/N=3) were1.5μg/ml,3.0μg/ml,15μg/ml and1.5μg/ml, respectivelywith good linearity. The interference of vitamin tablets was effectivelyeliminated. The recoveries of90.0%～110.0%of fat-soluble vitaminssample were obtained, with RSD ranged0.53%~5.46%.The fourth part of the work is to establish a method to analyze sixkinds of water-soluble vitamins (niacin, vitamin B1, vitamin B4, vitaminB5,vitamin B6, vitamin B12) in sports drink by using the optimizedpCEC-UV system. The separations were performed on a hydrophilicreversed-phase C18capillary column. The mobile phase was acetonitrile-water (containing20mM phosphate buffer solution) at a pump flow rate of0.15mL/min with the separation voltage of-5kV. Six water-solublevitamins were baseline separated within7min in gradient pCEC mode.The detection limits of each vitamin (S/N=3) were0.5μg/ml,1.0μg/ml,0.5μg/ml,1.5μg/ml,0.5μg/ml and1.0μg/ml, respectively with goodlinearity. The interference of sports drink was effectively eliminated. The recoveries of90.0％～110.0％of the watert-soluble vitamins wereobtained, with RSD ranged0.49%~4.21%.Based on the existing pressurized capillary electrochromatographysystem, we introduced autosampler and nano injection valve (10nL). Theformer solves the problem of automation of the injection system, the latteris introduced into the system to achieve accurate quantification and alsoimprove the precision of the analysis. The optimized pressurized capillaryelectrochromatography system was evaluated and then utilized in realsample analysis, which further confirmed its improved accuracy andprecision in the quantitative aspects.In the last chapter, we summarized the research and speculated on thefuture prospects.