| In recent years, with the rapid development of our country economy, the improvment of people’s living standards, the increase of demand, such as health and living environment, the quality of life and health level, many originally identified as non-toxic material, its security need to be reassessed, and in-depth researched. High performance capillary electrophoresis (HPCE), with its fast analysis speed, high separation efficiency, less sample quantity, low organic solvent consumption, simple pretreatment, has been widely used in health safety testing, especially in the determination of analytes in g/kg or percentage concentration of complex food, cosmetics. This paper maily focus on the simultaneous separation and determination of ten preservatives in ten sample matrixs and the accurate assay of thioglycolic acid in cosmetics. The thesis is composed two parts:In the first part, an improved micellar electrokinetic capillary chromatography method (MEKC) for the simultaneous determination of ten preservatives in ten types of food matrices was developed. Sample pretreatment methods for the effective extraction of ten preservsatives (dehydroacetic acid (DA), sorbic acid (SA), benzoic acid (BA), methyl p-hydroxybenzoate (MP), ethyl p-hydroxybenzoate (EP), propyl p-hydroxybenzoate (PP), butyl p-hydroxybenzoate (BP), isopropyl p-hydroxybenzoate (IPP), isobutyl p-hydroxybenzoate (IBP) and isoamyl p-hydroxybenzoate (IAP)) from ten kinds of food samples (soy sauce, chili sauce, jam, abalone sauce, seasoning sauce, pickles, ham, beverages, preserves, jellies, margarine, cheese, pastry, moon cakes) were systematically investigated. The types and contents of solvents in sample solutions were also optimized in detail. The ten preservatives were well separated from each other using an uncoated fused-silica capillary with50μm i.d. and70cm total length (effective length:60cm). The running buffer was15mmol/L Na2P4O7+60mmol/L H3BO3+100mmol/L SDS. The sample extraction solution varies with the types of food sample matrice. Three kinds of sample buffer solution were optimized as follows:1#. F(1.5mmol/L sodium tetraborate+6mmol/L boric acid):V (acetonitrile)=95:5;2#. V (25mmol/L acetic acid):V (acetonitrile)=95:5;3#.V (5mmol/L acetic acid):V (acetonitrile)=95:5. A content of five percent of acetonitrile is needed to ensure the resolution and the solubility of the preservatives in the injected sample solutions. The separations were performed at a constant voltage of25kV. The injection time was15s. The detection wavelength was at214nm. The limit of detection (LOD)(S/N=3) and limit of quantitation (LOQ)(S/N=10) were0.4-0.5mg/L and1.2～1.5mg/L, respectively. The correlation coefficient (r) values of the calibration curves were all greater than0.999. The recoveries of the samples at the concentrations studied were in the range from83.1%～116.3%. Relative standard deviations were all less than6.1%. Four hundred and thirteen food samples (111soy sauce,55sauces,30pickles,36ham,21preserves,38beverages,22cheese,57pastry,23moon cakes and20jellies) collected from the local farmers’market, ordinary and high grade supermarkets were analyzed by the current MEKC method and satisfactory results were obtained. Some of the results in soy sauce samples were compared with the HPLC method. They were in good agreement with those of HPLC method. The improved method with high separation efficiency, simple sample pretreatment and high throughputs could meet the needs for routine analysis of the ten preservatives in ten kinds of food products.The second part introduced a novel method for the accurate assay of TGA in cosmetics by capillary zone electrophoresis (CZE). Several key parameters, including the buffer concentration and pH, the type and concentration of additives, and concentration of sample buffer, which influence quantitative analysis and separation of TGA in cosmetic samples, were investigated in detail. The analysis was carried out using an uncoated capillary with50μm i.d and40.2cm (effective length:30cm) total length. The running buffer was300mmol/L Na3PO4(pH12.60) solution containing0.5mmol/L CTAB as electroosmotic flow modifier. A1:10dilution of the running buffer was used as the sample buffer. The separation was carried out at-5kV constant voltage conditions (current about-124μA). The detection wavelength was set at236nm. The injection time was10s. The relative standard deviations (RSDs) of corrected peak area precisions of the TGA were in the range of0.5%～4.3%. The RSDs of migration time were less than0.3%. The LOD (S/N=3) and LOQ (S/N=10) were2mg/L and6mg/L, respectively. The corrected peak areas versus the concentrations of TGA showed a good linear relationship within the range of6～1000mg/L, with a correlation coefficient (r) of0.9998. The average recoveries at the three spiked levels (125,250and500mg/L) were96.9%,102.3%and94.0%with RSDs2.1%,3.9%and2.2%, respectively. The method was cross-validated by both high performance liquid chromatographic and ion chromatographic method. Eighty-five commercial depilatory creams and hair-treatment products were analyzed with satisfactory results. |
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