Study On The Separation Of Acidic Artificial Pigments By Pressurized Capillary Electrochromatography

Acidic artificial pigments,which was of a good water solubility and strong ionic characteristic,are difficult to gain efficient separation by the conventional chromatography in the isocratic elution mode with a single interaction.Pressurized capillary electrochromatography(pCEC),a new technology combining the high efficiency analysis of capillary electrophoresis(CE)and the high selectivity of high performance liquid chromatography(HPL.C.),has been widely used in recent chromatographic researches.Based on pCEC method,effects of different functional monolithic columns on the separation of acidic artificial pigments one-dimensional electrochromatography separation and the continuous multiple pattern separation technology of two-dimensional electrochromatography have been investigated.and the multiple interactions including electrophoresis,ion exchange and chromatography retention in the continuous two-dimensional electrochromatography was discussed,An efficient separation of anionic acid synthetic pigment by pCEC has been successfully achieved.There are four chapters in this paper as below:In chapter 1,a review on the structural properties,characteristics and current development on the separation technology of edible synthetic pigments were presented.The technique principle of the pressurized capillary electrochromatography and the separation mode as well as the development of two-dimensional chromatography were described,and then the topic basis and the research content of this study were summarized.In chapter 2,based on cationic charged POSS hybrid silica-gel monolithic column,a research on the separation of acidic pigments by capillary electrochromatography with strong hydrophilic and ion-exchange mixed mode was carried out.Benzyl vinyl three methyl ammonium chloride(VBTA)was used as the functional monomer,and its content was optimized The retention behaviors of neutral substance,charged substance and acid pigment on POSS-VBTA column were investigated.The-POSS-VBTA monolithic column showed strong hydrophilicity arid significant eletrostatic adsorption,and thus acidic pigments such as lemon yellow,sunset yellow,allura red and brilliant blue could be effectively eluted due to their strong retention.In chapter 3,the separation of acid pigment was fulfilled by capillary electrochromatographywith neutral POSS matrix organic-silica hybrid monolithic column.To avoid the strong electrostatic interaction between acidic pigments and the monolithic stationary phase,the neutral hydrophilic POSS-HEMA matrix monolithic column was prepared and applied in this study.The chromatographic separation behaviors of neutral and anionic acidic pigment were investigated under different buffer salt and acetonitrile contents.Under the optimum comdition that the mobile phase was composed of acetonitrile and triethylamine at 40:60(triethylamine 3mmol/L,pH 6.50),the pressure was of 4.4 Mpa(500 psi)and the separation voltage was+15 kV,baseline separation of four acidic pigments including lemon yellow,sunset yellow,allura red,and brilliant blue could be gained in 7 minIn chapter 4,the continuous two-dimensional pressurized capillary chromatographic separation technology was studied and applied to acid pigments.The separation of six acidic pigments viz.sunset yellow,allura red,amaranth,carmine,and brilliant blue has been obtained by pCEC.The continuous two-dimensional separation column was constructed,which included a 9 cm quartz capillary,and a 16 cm long ODS-packed column.The separation behavior of acid pigment on an one-dimensional ODS-packed column and the continuous two dimensional column were studied.The mechanisms of the separation in two dimensional colum by pressurized capillary electrochromatography was discussed,and the optimization of the parameters such as buffer salts concentration,pH and high voltage was also studied.under the optimum conditions,a isocratic separation of 6 acidic pigments(viz.lemon yellow,sunset yellow,red temptation,amaranth,carmine and brilliant blue)could be achieved in 16.0 min by the 2-D pCEC technology.Applied to the commercial beverage samples,The recovery rate was gained in the range of 74.8-92.7%with the RSD of peak area less than 4.7%.