Micron-sized cellulose microspheres were prepared through sol-gel method using NaOH/urea solution to dissolve cellulose,then cross-linked by 1,6-hexanylene diisocyanate(HDI),toluene 2,4-diisocyanate(TDI)and 1,4-phenylene diisocyanate(PDI),respectively.The reaction conditions for partial modification of the microspheres were studied.The degree of substitution(DS)in cellulose was controlled by adjusting the reaction conditions.HDI-crosslinked microspheres were partially modified with phenyl isocyanate to obtain chiral stationary phases(CSPs).The CSPs of a lower degree of crosslinking(DC)showed better chiral recognition ability than those of a higher DC.Meanwhile the CSPs prepared by premodification exhibited better chiral recognition ability than those prepared by pre-crosslinking.
The aim of this work is optimizing the techniques to prepare pure cellulose microspheres, which are used as packing adsorbents for high-performance liquid chromatography. Thereupon, cellulose was dissolved in a pre-cooled NaOH/urea solution, from which various-size microspheres were prepared. The volume-average diameters were controlled approximately at 30 μm, 8 μm and 4 μm grades when cyclohexane, liquid paraffin and pump oil were used as dispersants, respectively. The present investigations reveal that higher viscosity dispersant is suitable for the preparation of smaller-size microspheres, while larger size microspheres are prepared preferably using lower-viscosity dispersant. The chiral stationary phase derived from 8 μm grade microspheres can separate the enantiomers of efavirenz.
