Supramolecular effects in the chiral discrimination of meta-methylbenzoyl cellulose in high-performance liquid chromatography

A series of chiral stationary phases (CSPs) were prepared from meta-methylbenzoyl cellulose (MMBC) by deposition on silica using different methods (evaporation or precipitation) and various solvating agents. The chromatographic properties of these CSPs were evaluated using a set of racemic compounds. Both the method of deposition and the solvating agent have a profound influence on the optical resolving power of the MMBC CSPs. Surprisingly, variations were observed not only in the enantioselectivities, but also in the enantiomeric elution order of some of the substances. The precipitation method of deposition is preferable to coating by evaporation. The highest enantioselectivities were obtained with the phases prepared by precipitation of MMBC, either from pure methylene chloride (MC-P), or from methylene chloride solution in the presence of phenol (MC-PHN). These two CSPs show complementary properties in terms of resolution for most compounds investigated and in some cases exhibit opposite optical discrimination patterns. This phenomenon points to the importance of the supramolecular structure of the chiral polymer MMBC on its chiral recognition capability.