DYNAMIC COLUMN-COATING PROCEDURE FOR CHIRAL LIGAND-EXCHANGE CHROMATOGRAPHY

The preparation of HPLC columns for chiral ligand-exchange chromatography by dynamic adsorption of a histidine-based chiral selector (N(tau)-n-decyl-L-histidine, LNDH) on commercial reversed-phase, C18 columns was investigated. The most suitable solvent for column preparation was sought through a study of the behaviour of LNDH on the reversed-phase column eluting with different methanol-water ratios at varying pH. It is shown that the use of an aqueous solvent instead of pure methanol is advantageous, despite the decrease in LNDH solubility, and that the solvent pH must be controlled. Open and closed-cycle procedures for flowing the selector solution through the column are compared through a study of chromatographic retention, selectivity and efficiency parameters of selected enantiomers. Even though no significant difference in column loading was found between the two procedures, the open cycle method gave rise to more efficient and selective chiral columns.