In this study we attempted to describe in a comparative manner the enantioselectivity performance of six different polysaccharide- and two strong cation exchanger-type chiral stationary phases (CSPs) for the resolution of free and N-protected β-carboline derivatives. On commercially available cellulose- or amylose-based CSPs, the enantioseparations were carried out in normal-phase mode by variation of the nature and the concentration of the alcohol modifier in n-hexane as mobile phase. With the application of strong cation exchanger-type CSPs, the enantioseparations were optimized by the variation of methanol-acetonitrile bulk solvent compositions in the presence of various amounts of acid and base additives acting as counter-ions. Detailed thermodynamic investigations revealed that in all cases the enantioseparations observed were enthalpically driven, i.e. the retention and selectivity decreased with increasing temperature. Elution sequences were determined routinely; no general rule was found on polysaccharide-based CSPs, while on the two enantiomeric strong cation exchanger-type CSPs the predicted reversal of the elution sequence could be confirmed on switching from one enantiomeric CSP to the other form.
Lajkó, G., Grecsó, N., Megyesi, R., Forró, E., Fülöp, F., Wolrab, D., … Ilisz, I. (2016). Enantioseparation of ß-carboline derivatives on polysaccharide- and strong cation exchanger-based chiral stationary phases. A comparative study. Journal of Chromatography A, 1467, 188–198. https://doi.org/10.1016/j.chroma.2016.05.040