HPLC based on chiral stationary phases (CSPs) has become one of the most attractive approaches to chiral separations, due to their simplicity for determining optical purity and easy extension to the semipreparative and preparative scales. 1 One of the major problems in using many CSPs is their narrow range of analyte applicability; they can only discriminate a limited number of specific types of chemical entities, and it is frequently necessary to derivatize the compounds of interest to achieve separation. 2 On the other hand, the polysaccharide derivative-based CSPs developed by Okamoto and coworkers [3][4][5][6][7] have proven to be highly versatile and rugged. Okamoto reported that the resolution of 483 racemic mixtures on cellulose and that 80% of them were successfully resolved on either the cellulose or amylose tris(3,5-dimethylphenylcarbamate) (CDMPC or ADMPC). 8 Silica is the most popular choice for support of HPLC stationary phase ligands due to the mechanical strength, wide range of particle and pore dimensions, pore structure and wellestablished silane chemistry. However, silica and bonded phase ligands have stability problems. Silica dissolves in mobile phase buffered at or above pH 8 with loss of bonded phase ligand and column packing. 9 Loss of organosilanes from the silica surface via hydrolysis proceeds rapidly at low pH (< 3) and at high temperature (≥ 40˚C). These deficiencies of the column packing create problems of poor injection reproducibility, poor peak shape, and high backpressure, thus making method development tasks difficult. Siloxane-bonded silica phases with improved hydrolytic stability at extreme pH for use in reversedphase liquid chromatography were introduced. 10-13 However, careful choices of operating conditions, such as the use of acetonitrile instead of methanol, the use of boric acid or organic buffers in low concentration and low temperature, are still required to achieve acceptable column lifetimes. [14][15][16][17] Zirconia particles are very robust material; they show no detectable signs of dissolution over the pH range from 1 to 14 and have been used for prolonged periods at temperatures up to 200˚C in chromatographic separations. Thus, zirconia has received considerable attention as a stationary phase support for HPLC over the last decade. 18,19 One of us has been working to develop efficient and chemically stable CSPs on zirconia substrates. [20][21][22][23] Bare zirconia cannot be covalently modified like silica due to the instability of Zr-C and Zr-O-Si bonds in water. 24 Zirconia-based CSPs reported have thus been prepared by coating chiral selectors on zirconia surface by utilizing Lewis acid-base chemistry. Recently we reported chiral separation of N- (2,4-dinitrophenyl) Porous zirconia particles are very robust material and have received considerable attention as a stationary phase support for HPLC. We prepared cellulose dimethylphenylcarbamate-bonded carbon-clad zirconia (CDMPCCZ) as a chiral stationary phase (CSP) for separation of enantiomers of a set of...
