| The thesis is mainly focused on the determination ofα-lactalbumin (α-Lac),β-lactoglobulin A (β-lgA) andβ-lactoglobulin B (β-lgB) in the dairy products by high performance capillary electrophoresis (HPCE) and high performance liquid chromatography (HPLC). It consists of the following four sections:(1) Two new methods for the determination ofα-Lac,β-LgA andβ-LgB in the whey protein by HPCE and HPLC were established. The CE analysis was carried out in an uncoated capillary with 50μm i.d and 57 cm total length. The running buffer was 0.5 mol/L H3BO3 containing 25 mmol/L HP-β-CD and 0.8 g/L PEO 4000 000 (pH 9.1, adjusted by 2 mol/L CsOH). The sample buffer was 50 mmol/L HAc. The detection wavelength was 214 nm. The factors that influence the separation of the three proteins, such as the kind, concentration and pH of the buffer, the buffer additives, separation voltage, were investigated in detail. The RSDs of the method for the three proteins was 3.5, 3.8 and 6.6%, respectively. A good linear relationship existed for the three proteins in the range from 50 mg/L to 400 mg/L with correlation coefficients (r) of 0.9983, 0.9972, and 0.9974, respectively. The LODs (S/N=3) were 10, 15, and 12 mg/L, and LOQs (S/N=10) were 30, 50 and 40 mg/L, respectively. The HPLC analysis was performed with a CAPCELL PAK C8 SG 300(200 mm×4.6 mm, 5μm) column and a gradient mobile phase mixture employing acetonitrile and water solution containing trifluoroacetic acid and sodium cholride. Because the migration time of Lf andα-Lac were the same, onlyβ-lgA andβ-lgB could be determined by the method. The linear relationship was observed in the range of 15 - 500 mg/L, with a correlation coefficient (r) of 0.9998 and 0.9997, respectively for the two proteins. The LODs (S/N=3) were 4 and 3 mg/L, and LOQs (S/N=10) were 12 and 10 mg/L. The RSDs of method for the two proteins were 3.6% and 3.2%. The two methods were used to determine the proteins in the same samples and satisfactory results were obtained. With the advantagement of having good accuracy and a shorter analysis time, lower solvent consumption and better column efficiency, CE was considered to be a better method compared with HPLC,(2) Based on the developed CE method, the contents of above three proteins in the diary products were determined. The samples include whey protein power, raw milk, bovine colostrum, liquid milk, yogurt and formula power from different manufactures and countries. The results indicated that whey protein power has the highest content of the above three proteins, the second are bovine colostrum, the third are raw milk. The content of the above three proteins in liquid milk had a relationship with the storage duration; normally the longer the duration the less the protein content. The contents ofα-Lac in most of the yogurt were higher than those in UHT milk. The contents of proteins in infant formula were decreased when the stage was raised. Infant formula with the same stages but different brands and countries has dramatic differences in the contents ofα-Lac, and the contents of the above three proteins in imported formula are not always higher than those from domestic ones. The results provide a valuable asset for the protein analysis in milk and milk products.(3) In the CE analysis, different concentrations of HAc and TCA for the removal of interfering proteins in raw milk, imported and domestic infant formula, and yogurt were investigated in detail. It was shown that TCA is better than HAc for eliminating of interfering proteins in the above four samples. The interfering proteins in 2 mL of raw milk could be eliminated by 3 mL of 100 g/L TCA. 0.5 g of imported or homemade infant formula needs 5 mL of 10 g/L and 20 g/L TCA to remove the interfering proteins, respectively. For 2 g of yogurt, 5 mL of 20 g/L TCA is needed. The present reaserch may add valuable information for the sample pretreatment of interfering protein-containing samples (such as raw milk, infant formula and yogurt).(4) For the determination of the IgG in the health food by affinity liquid chromatography, GB method was improved by the modification of the liquid chromatography instrument in our lab. The two methods were used to determine the same health foods. The results obtained by CE and HPLC have no significant differences. The improved affinity liquid chromatography method was also used to determine the content of IgG in bovine colostrum, raw milk and human milk samples..
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