The Influence of Temperature, Ultrasonication and Chiral Mobile Phase Additives on Chiral Separation: Predominant Influence of β-Cyclodextrin Chiral Mobile Phase Additive Under Ultrasonic Irradiation

Abstract

This paper introduces a technique for resolving amino acids that combines the advantages of the conventional CSP (chiral stationary phase) method with the CMPA (chiral mobile phase additive) method. A commercially available chiral crown ether column, CROWNPAK CR(+), was used as the CSP and three cyclodextrins (-CD, -CD, HP--CD) were used as the mobile phase additives. Chromatographic resolution was performed at and with or without sonication. A comparison of the chromatographic results under ultrasonic conditions with those under non-ultrasonic conditions showed that ultrasound decreased the elution time and enantioselectivity at all temperatures. In the case of the -CD mobile phase additive, the elution time and enantioselectivity under ultrasonic condition were significantly higher than under non-sonic condition at all temperatures. Commercially available Chiralpak AD, Whelk-O2 and Pirkle 1-J columns were used as CSPs to examine more meticulously the effects of ultrasonication and temperature on the optical resolution. The optical resolution of some chiral samples analyzed at and with or without sonication was compared. As in the previous case, the enantioselectivity was lower at but similar enantioselectivity was observed at .