Immobilization And Chiral Recognition Ability Of Polysaccharide Cyclohexylcarbamate-based Chiral Packing Materials

Chiral stationary phases(CSPs) for high-performance liquid chromatography (HPLC) hasdrawn much attention within the past few decades and is considered as most usuful way forboth the analysis of enantiomers and the separation of enantiomers. Among those CSPs forHPLC, polysaccharide phenylcarbamate and benzoate derivative-based CSPs are well-knownto exhibit high chiral recognition while alkylcarbamate derivatives of polysaccharides exhibitmuch lower chiral recognition abilities as CSPs for HPLC. However, alkylcarbamatederivatives can be used as CSPs both in TLC and HPLC while phenylcarbamate and benzoatederivatives can not and that is because alkylcarbamate derivatives contain no phenyl groupswhich strongly absorb ultraviolet (UV) light.Those high performanced polysaccharide-based CSPs are prepared by coatingderivatives on silica gel and this means some solvents such as chloroform, tetrahydrofuran,acetone, etc., which can dissolve or swell the derivatives cannot be used as eluents. Howeverthe use of the prohibited eluents may result in a better resolution, reversed elution order of theenantiomers and higher solubility of a sample which are important factors for the efficientseparation of enantiomers by HPLC. The immobilized-type CSPs can overcome the strictsolvent limitation of eluents and achieve a better resolution in enantiomeric separation andpreparation.Based on this background, this paper aimed at synthetizing a series of novelpolysaccharide cyclohexylcarbamate derivatives and developing a immobilized-type CSPsbased on this type of derivatives. Moreover, polysaccharide cyclohexylcarbamate derivativescan be applied as CSPs in both HPLC and TLC and this work consists three parts:First, polysaccharide cyclohexylcarbamate derivatives bearing a controlled amount of a3-(triethoxysilyl)propyl residue were synthesized by a one-pot method. FT-IR spectrum and1H NMR spectrum were introduced to characterize structures of those derivatives.Second, prepare the coated-type and immobilized-type CSPs by coating, immobilizationand packing procedures. The amounts of the immobilized polysaccharide derivatives werecalculated from the content of the organic materials on the CSP estimated bythermogravimetric analysis (TGA).At last, the chiral reccgnition abilities of the obtained polysaccharide cyclohexyl- carbamate derivative-based HPLC and TLC CSPs were evaluated by separating10typicalracemates. Relations among introduction of3-(triethoxysilyl)propyl residue, theimmobilization efficiency and chiral recognition ability were discuss and further chiralrecognition mechanisms were also addressed.