Preparation And Performance Evaluation Of Chitooligosaccharide Based Hydrophilic Materials For Chromatographic Separation

At present,the development of hydrophilic interaction liquid chromatography(HILIC)separation materials with novel structures and excellent properties mainly consider these two aspects:(1)hydrophilic properties of chromatographic materials;(2)stability of chromatographic materials.It is well known that polysaccharides have a large number of hydrophilic groups including hydroxyl,amino,and/or carboxyl groups,which can be used to modify their chemical structures to increase the stability,therefore leading to being one preferential raw material for the preparation of high-performance stationary phases.Based on the above considerations,in this study chitooligosaccharides(COSs)and its derivatives were used to prepare three kinds of COS chromatographic separation materials,and the corresponding characterizations and chromatographic evaluations were carried out.The main research works are as follows:(1)A novel chromatographic stationary phase material was prepared by directly inmobilizing the chitooligosaccharide onto the surface of silica gel through a classic synthesis method,"opening reaction of alkylene oxide and amine".The obtained chromatographic material was characterized by infrared spectroscopy and elemental analysis,respectively.Using various nucleosides and bases as probes,the chromatographic separation capabilities of the obtained materials were examined in the HILIC mode.And the retention behaviors were studied under different chromatographic conditions including water content of mobile phase,salt concentration,buffer pH value,and column temperature.Moreover,the hydrophilic chromatographic selectivity was investigated by separating five water-soluble vitamins and four salicylic acid compounds.These results showed that the COS chromatographic separation material accorded with the classic characteristics of HILIC,and this synthesis way was feasible.(2)COS was modified with sodium benzaldehyde-2-sulfonate to increase its hydrophilicity and stability.And then a sodium benzaldehyde-2-sulfonate derivatized COS chromatographic material was successfully prepared.The obtained material was characterized by infrared spectroscopy,elemental analysis,and thermogravimetric analysis.In the HILIC mode,the influences of water content of mobile phase,salt concentration,buffer pH value,and column temperature on the retention behaviors of seven nucleoside and bases.The chromatographic separation performance of the obtained material was also investigated in the separation of seven nucleosides and bases,five kinds of water-soluble vitamins,and five kinds of salicylic acid related compounds.Additionally,the application of the obtained stationary phase in the test of melamine in milk sample was further observed.These results show that the obtained material could display the powerful chromatographic performance in the separation of vavious polar analytes and exihibited a good potential in the practical applications.(3)Two COS quaternary ammonium salts with different substituted degree of quaternization were prepared by 2,3-epoxypropyltrimethylammonium chloride modified COS,and were bonded onto the silica gel surfaceto obtain two novel stationary phases.The derivatives and the corresponding separation materials were characterizated by nuclear magnetic resonance,infared spectroscopy,and elemental analysis,respectively.Under different hydrophilic chromatography conditions,the chromatographic characteristics of these two materials were investigated.Additionally,the comparition between the chromatographic performances of these two materials was also previded.These results show that the separation performance of these two materials not only depends on the subsitituted degree of quaternization but also the bonding density of functional groups on the surface of silica gel.