Chiral resolution of histidine using an anti-d-histidine l-RNA aptamer microbore column

In this paper, we report a new anti-amino acid aptamer chiral stationary phase (CSP). The enantiomers of histidine were separated using an immobilized histidine-specific l-RNA aptamer (40-mer) and an aqueous buffer as mobile phase. The effects of the variation of different operating parameters, including the mobile phase pH and the MgCl2 concentration as well as the column temperature, on the solute retention were assessed. The results suggested that (i) the protonated form of histidine was involved in the stereospecific RNA binding and (ii) Mg2+ was essential for the target enantiomer binding to the specific aptamer sites. From a practical point of view, it appeared that the baseline resolution in a minimum analysis time can be achieved at a column temperature of 35 °C for an eluent containing 10 mM of MgCl2, pH 5.5.