Reversal of Elution Order between Enantiomers of Binaphthol on an Immobilized Polysaccharide-Based Chiral Stationary Phase

Abstract

Enantioseparation of 1,1 0 -bi-2-naphthol (BINOL) was performed on an immobilized polysaccharide-based chiral stationary phase (CSP), Chiralpak IA, in the normalphase mode. The effects of polar modifier in the mobile phase and column temperature on retention, enantioseparation, and elution order were investigated. An interesting reversal of elution order for BINOL was observed. When ethanol was used as a polar modifier, R-BINOL was eluted first with marginal enantioseparation. Excellent enantioseparation was obtained when ethanol was replaced by 1-propanol, and S-BINOL was eluted first, this effect being retained with 2-butanol, 1-butanol, 1-pentanol or 1-hexanol as the modifier. When isoamyl alcohol was used, reversal of elution order was again observed, i.e., R-BINOL eluted first with marginal enantioseparation, similar to the case of ethanol. When cyclohexanol and cyclopentanol were used, R-BINOL was still eluted first, but enantioseparation was as good as with 1-propanol as the modifier. This is the first report of large enantioseparation obtained in both elution orders for a given selector/selectant system. A retention model based on stoichiometric displacement theory for retention (SDT-R) was investigated to fit the chromatographic data. The reason for solvent-induced reversal of elution order was elucidated based on a derivation of the retention model. Reversal of elution order for BINOL induced by the content of isoamyl alcohol was also predicted based on the model and confirmed by experiment.

Solvent‐induced enantioselectivity reversal in a chiral metal organic framework

“…The enantioseparation of 1,1′‐bi‐2‐naphthol was investigated on a polysaccharide‐based chiral stationary phase. Upon changing the polar modifier (1.37 M concentration) present in the n‐hexane mobile phase from ethanol to 1‐propanol, a reversal in elution order and improvement in enantioselectivity was observed [23]. In another study, vibrational circular dichroism coupled with density functional theory calculations were employed to investigate the enantioseparation of two chiral analytes on a cellulose and amylose column under chromatographic conditions.…”

Reversal of elution order of N‐(2,4‐dinitrophenyl)‐proline and N‐(2,4‐dinitrophenyl)‐serine in HPLC by BSA chiral stationary phase

“…Moreover, column temperature , concentration of sample , types and content of organic modifiers , the nature and concentration of acidic additive may have significant effect on elution order of enantiomers in chromatographic separation. However, reversal of elution order induced by changing pH and organic modifier in reversed‐phase mode has been rarely reported till now .…”

Solvent Induced Enantioselectivity Reversal in a Chiral Metal Organic Framework

“…The enantioseparation of 1,1'-bi-2-naphthol (BI-NOL) was investigated on a polysaccharide based chiral stationary phase. Upon changing the polar modifier (1.37 M concentration) present in the n-hexane mobile phase from ethanol to 1-propanol, a reversal in elution order and improvement in enantioselectivity was observed (20). In another study, vibrational circular dichroism coupled with density functional theory calculations were employed to investigate the enantioseparation of two chiral analytes on a cellulose and amylose column under chromatography conditions.…”