Synthesis And Application Of Immobilized-type Chiral Stationary Phases Based On Cellulose Derivatives For HPLC

High performance liquid chromatography (HPLC) with chiral stationary phases (CSPs)is well known as a fast and efficient technique for chiral separation. The phenylcarbamatesand benzoates of cellulose have been shown excellent chiral recognition and have been widelyused. There are two types of CSPs used in HPLC: coated-type CSPs and immobilized-typeCSPs. Coated-type CSPs are easily prepared and can show good chiral recognition abilities.But some common solvents, such as chloroform, tetrahydrofuran and acetone, are forbiddento used as eluent, because the polysaccharides-based CSPs can be damaged for theirdissolution or swelling in those solvents. Therefore, the chemical immobilization ofpolysaccharide derivatives on silica gel has been discovered as a direct approach to confer auniversal solvent compatibility to these kinds of CSPs.In this study, six regioselectively substituted cellulose derivatives were synthesized by afour-step process, and their structures were characterized by1H NMR measurement and FT-IRspectroscopy. In order to prepare the immobilized-type CSPs, vinyl groups were introduced tothe6-position of the glucose units. Under the ultraviolet irradiation, the vinyl-bearingcellulose was crosslinked by copolymeration initiated by azobisisobutyronitrile (AIBN). Theperformance of the coated-type and immobilized-type CSPs were tested by FT-IRspectroscopy and thermo gravimetric analysis (TGA). The rates of cellulose derivativescoated or immobilized on the silica gel were calculated. The surface morphologies ofimmobilized-type CSPs were also characterized by scanning electron microscope (SEM). Theresults show that the macroporous silica gels were effectively coated by cellulose derivativesvia cross-linking polymerization of vinyl group.Coated-type and immobilized-type cellulose derivatives CSPs were packed to thestainless steel column by slurry method. And the chiral recognition abilities of coated-typeand immobilized-type CSPs for seven typical racemates were evaluated by HPLC. Meanwhile,the chiral recognition abilities of these immobilized CSPs were compared with those ofcoated-type CSPs and commercialize chromatography columns. The prohibited solvents forthe coated-type CSPs, such as chloroform and tetrahydrofuran, could be used for these novelimmobilized-type CSPs. Furthermore, the effect of temperature on the chiral recognition ability was also investigated.