Effect of injection diluent on a chiral separation on an amylose S-α-methylbenzylcarbamate chiral stationary phase (short communication)

A method to separate the four stereoisomers of a chiral thiazolidine-2, 4-dione containing two stereocenters was developed. This thiazolidine-2,4-dione is susceptible to epimerization through an enol-type intermediate, predominantly in protic solvents. While acetonitrile would provide both necessary sample solubility and sample stability for chromatographic analysis, significant peak fronting was observed when it was used as the diluent with a concomitant loss in resolution. Similar fronting was not observed when preparing sample solutions in ethanol, 2-propanol, methanol, or a 1:1 mixture of methanol and ethanol. The source of this fronting was explored by performing two sample loading studies: constant sample loading with varying volume and constant volume with varying loading. Peak asymmetry was used as a quantitative measure of the resulting peak fronting. These analyses indicate that the fronting observed when using acetonitrile as a diluent could arise due to a strong-solvent like effect of this solvent and or the solubility of the solute in the microenvironment with this combination of column packing and eluent.