Enantiomeric resolution on Chiral-AGP with the aid of experimental design - Unusual effects of mobile phase pH and column temperature

Baseline separation of the enantiomers of two structurally related dihydro-pyranoimidazopyridines was performed within 15 min on Chiral-AGP by using experimental design. The retention times of the enantiomers were found to have an optimum at a mobile phase pH of around 7. However, the enantioselectivity increased with increasing mobile phase pH. Besides the interesting effect of pH, only a minor decrease in the enantioselectivity was obtained by increasing the column temperature. The variables, column temperature, mobile phase pH and concentration of acetonitrile, influenced all four stereoisomers in the same way. However, the statistical model separated the loadings i.e., the influence of the descriptor variables on the capacity factors of the first and last eluted enantiomers of the two solutes investigated, which indicated differences in retention mechanisms.