In this thesis we utilize capillary electrophoresis (CE) and MALDI-TOF/MS technique to investigate the adsorption and desorption behaviors of α-casein tryptic digests on chitin and chitosans with degrees of deacetylation (DDA) of 95%, 54%, 34%. The elution orders of the peptide fragments in CE electropherogram were determined by HPLC purification of the tryptic digests and MALDI-TOF/MS identification of the peptide molecular weights. The ratios of residual peptides to original tryptic digests were calculated from the peak areas in CE electropherograms. The effects of concentration and polarity of desorbents on the peptide desorption efficacy were studied for the four adsorbents. Peptide desorption ratios were also obtained from CE electropherograms. According to our results, the phosphopeptides of the peptide mixtures almost completely adsorbed onto the four chitosan adsorbents. The DDA95% chitosan seemed to have stronger affinity for peptide fragments and thus resulted in lower desorption ratios. In order to achieve better desorption efficacy for the four adsorbent systems, 0.15%, 1.5%, and 15% ammonia aqueous solutions, as well as 1.5% NH3 in 30% ACN and in 30% MeOH solutions were used as desorbents for the peptide desorption reaction. In general, low concentration NH3(aq) would result in poor desorption efficacy. For chitosans with high and medium DDAs, 1.5% and 15% NH3(aq) resulted in similar desorption ratios. For chitosans with high and medium DDAs, the additions of both ACN and MeOH would increase the desorption ratio. However, for low DDA chitosan, no enhancement of desorption ratio was observed with MeOH addition, and lower desorption efficacy was found with ACN addition