Unusual Endothermic Retention and Reversal of Elution Order in Enantioseparation of Binaphthol on a Coated Amylose-derived Chiral Stationary Phase

Abstract

Several chiral compounds,including 1,1′-bi-2-naphthol(BINOL),binaphthol diacetate,binaphthol disulfonate,dibromobinaphthol,hydrobenzoin and naproxen,were enantioseparated on a coated amylose-derived chiral stationary phase,Lux Amylose-2,in the normal-phase mode.The effects of column temperature and polar alcohol modifier in the mobile phase on the retention,enantioseparation and elution order were investigated.Hydrobenzoin achieved an excellent enantioseparation no matter which alcohol was used as polar modifier(resolution being 17.76).Binaphthol diacetate,binaphthol disulfonate and dibromobinaphthol achieved baseline or partial enantioseparation(resolution being 3.43,2.56 and 1.47,respectively).Solvent-and temperature-induced reversals of elution order in the enantioseparation of BINOL were observed.An unusual endothermic characteristic was observed during the retention process of R-BINOL.The origin of the reversal of elution order and the chiral recognition mechanism were discussed.