Preparation Of Silica-based Chromatographic Microcolumns And Detection Of Melamine In Milk Powder

Food safety problem appeared frequently in recent years, Food safety is more and more important and urgent, it request high effective and fast of detection method, microcolumn analysis technology such as micro- high-performance liquid chromatography and capillary electrochromatography became the highlight of the food analysis. As the place and core of the separation, the property of chromatographic column decides the efficientof separation. This thesis explores the preparation, performance evaluation of the silica-based chromatography microcolumn incoluding packing column, entrapping fritless column and tandem stationary phases column, the applications in food industry.The inlet frit was prepared by the sol-gel technology and in-situ UV photo-polymerization, then packed 11cm stationary phase C18 by high pressure slurry packing, the outlet frit by sintering. The performance of the capillary columns was evaluated in terms of analysis times, column efficiency, column life, column reproducibility by the capillary LC and the capillary electro-chromatography modes. The four kinds of model compounds were separated under the optimized condition and theoretical plate height up to 7.20μm.A short length of a sol-gel monolith was initially prepared as the temporary frit in a 100μm inner diameter fused-silica capillary by an in situ photopolymerization. The packed 4μm octadecylsilane particles were then immobilized within the identical sol-gel solution through the same photopolymerization process. The prepared fritless capillary column was examined for the chromatographic performance by the self-developed capillary liquid chromatography system. Baseline separation of the model analytes was achieved including thiourea, benzene, toluene and ethylbenzene with the lowest theoretical plate height about 66μm for the retained component. A scanning electron micrograph was used to characterize the temporary frit and entrapped microspheres. The inorganic polymer matrix in the microsphere-packed column functioned to link microspheres at specific sphere-sphere and sphere-capillary contact points. Furthermore, the stability and porosity of the fritless column were systematically investigated by a simple flow method.Tandem separation beddings were prepared within the capillary tube with a photopolymerized monolith initially formed by sol-gel technology in combination with microspheric octadecylsilane material by slurry packing. The chromatographic performance of the tandem stationary phases was evaluated in detail by varying the flow rate and the composition of the mobile phase using a self-installed capillary HPLC system. For the tandem stationary phases with a forepart monolithic length of 11 cm and 1 cm the lowest theoretical plate height for the retained component was 26μm and 34μm, respectively. A scanning electron micrograph with different cross-sections of the column showed that a porous network formed in the center of the capillary and a homogenous slurry packing of C18 was obtained at the back part.It has established analytical method assemblingμ-HPLC internal standard determination for melamine in milk powder. The sample with 1% trichloroacetic acid precipitation protein purification was extracted by the supersonic vibration and centrifugation extraction, The chromatographic column self-made (effective length 29 cm, total length 37.5 cm, 5μm ODS), the acetonitrile and ion pair buffer solution as mobile phase, detection wave length 230 nm, The good linearity was in the range of from 0.1 to 1.2 mg/mL of melamine, and the coefficient 0.9962. The average recoveries of melamine are 93.25%.Cellulose tris (3,5-dimethylphenylcarbamate) chiral solid phase by bonded and coated method were synthesizedin, and the cellulose tris (3,5-dimethylphenylcarbamate) chiral column was packed by high pressure slurry packing in the 100μm fused silica capillary. Chromatographic performance was evalued by the self-assembled micro-HPLC, they have carried on the resolution to 18 kinds of raceme medicines and 14 kinds of chiral sample obtained separation under the optimized condition, this column displayed the good chiral separation performance.