Effect of column temperature on enantioseparation of dihydropyrimidinones using alcohol solvated Chiralpak AS and AS‐H columns

Abstract

In this study we report the application of column temperature programs to compare the chromatographic behaviors of four commercially available dihydropyrimidinone (DHP) compounds on Chiralpak AS and AS-H phases under different alcohol solvation conditions such as 1-propanol (1-PrOH), 2-methyl-1-PrOH (2-Me-1-PrOH), 1-butanol (1-BuOH), 2-BuOH, and tert-BuOH (t-BuOH) in n-hexane (n-Hex). It was observed that the apparent retention factors of the DHP compounds on the AS phase in t-BuOH/n-Hex mobile phase had the largest reduction (>27%) among the mobile phases studied after a heating and cooling temperature cycle (10 to 50 back to 10 degrees C). However, the average reduction of the apparent retention factors of the compounds on t-BuOH solvated AS-H was less than 4%. No clear trend of changes in the apparent retention factors on AS and AS-H columns was observed in other alcohol modified mobile phases. Step-temperature programs showed that alcohol solvated AS phase had larger changes in the apparent retention factors with time than those of AS-H phase at the elevated temperature step (50 degrees C). Both t-BuOH solvated AS and AS-H phases showed kinetic behaviors in chromatographic processes at the elevated temperature.