Study On Preparation And Chiral Recognition Of Polysaccharide Derivatives-Based Chiral Stationary Phases

Preparation and application of coated and immobilized polysaccharide derivatives-based chiral stationary phases (CSPs) is one of the promising research fields in separation sciences. Based on the analysis and evaluation of bibliographer, a series of the eight regioselective substituted polysaccharide derivatives-based CSPs, two immobilized-type cellulose-based CSPs by improved method and two coated-type composite CSPs by different mixing method were synthesized in the Dissertation. Their chiral discrimination abilities for racemic compounds were evaluated. And the influences of mobile phase polar additives and concentration, amount of diisocyanate, the substituents and their arrangement on enantioseparation were studied.Four cellulose derivatives having two different substituents at6-position and2-,3-positions of the glucose unit were prepared and evaluated as CSPs for HPLC. The obtained four cellulose derivatives were characterized by FT-IR spectrum,’H NMR spectrum, and elemental analysis, and the resolution of15racemates was studied. Additionally, the performances of the obtained CSPs were compared with that of Chiralcel OD, one of the most widely used CSPs. One CSP exhibited high chiral recognition, comparable to that of Chiralcel OD. One racemate was completely resolved on the CSP, while it cannot be resolved effectively on Chiralcel OD.Four regioselective substituted amylose derivatives with three different substituents at2-,3-, and6-positions of the glucose unit were prepared and evaluated as CSPs for HPLC. The influences of mobile phase polar additives and concentration on enantioseparation were studied. The chiral recognition of the four CSPs were compared to that of the commercially available Chiralpak AD containing amylose3,5-dimethylphenylcarbamate as chiral selector. Two of them showed higher chiral recognitions than Chiralpak AD for some racemates.The classical method for preparation of immobilized-type cellulose-based CSPs with diisocyanate as the linker was improved. Two different immobilized CSPs were prepared by using1,4-phenylene diisocyanate and4,4’-diphenylmethane diisocyanate as spacer arms. Compared with the classical diisocyanate method, the improved procedure avoided the derivatization and regeneration of6-hydroxyl groups of cellulose, and thus showed an advantage for simple and economical preparation. The relationships among the amount of diisocyanate used, immobilization efficiency, and enantioseparation on the obtained CSPs were investigated. Also, the solvent durability of the immobilized-type CSP was examined with eluents containing chloroform and tetrahydrofuran. By utilizing these eluents, the chiral recognition abilities of the CSP for most of the tested racemates were improved.Two coated-type composite CSPs were prepared based on cellulose tris(3,5-dimethylphenylcarbamate)(CDMPC) and amylose tris(3,5-dimethylphenylcarbamate)(ADMPC) by coating the corresponding derivatives onto3-aminopropyl silica gel separately and then mixing or by coating the mixed derivatives onto silica gel. The CSPs containing only CDMPC or ADMPC were also prepared for comparison. Investigations showed that the mixing method did not significantly influence the enantioselectivities. The composite CSPs generally show chiral recognition abilities intermediate between those of the two individual phases, while some racemates were poorer and at the same time, one were better resolved on the composite CSPs.