Chiral separation by simultaneous use of vancomycin as stationary phase chiral selector and chiral mobile phase additive

Improved chiral selectivity was observed for numerous compounds when vancomycin was added to the mobile phase on a Chirobiotic-V column. This chiral mobile phase additive (CMPA) is the same chiral selector as that bonded to the stationary phase of this Chirobiotic-V column. A substantial increase in the difference in enthalpy of transfer, ΔΔH, and in the difference in entropy of transfer, ΔΔS, for two enantiomers was observed when vancomycin was used as both the mobile phase and the stationary phase chiral selector. The importance of mobile phase composition, analytical column, CMPA concentration was investigated. Also, higher resolution was observed for the separations of acidic compounds when a fluidity enhancing solvent, such as fluoroform, was added into the mobile phase. However, the most commonly used fluidity enhancement solvent, CO2, was ineffective.