Capillary electrochromatography (CEC) has focused attention on complementary fields of research in recent times, since it combines the best features of both high-performance liquid chromatographic and capillary electrophoretic techniques. Although CEC enables researchers to separate a diverse range of analytes at very low sample concentration, preparation and characterization of robust columns remains a vital challenge in ensuring high separation resolution and efficiency. To this end, use of chiral poly(acrylamidopropyl) materials in the porous layer open tubular (PLOT) capillary electrochromatographic (CEC) format has been investigated for the enantioseparation of racemic mixtures of bioorganic molecules.

The PLOT capillary materials were synthesized by in-situ polymerization of 3-acryl-amidopropyl trimethylammonium chloride (APAT) and divinylbenzene (DVB) in the presence of heptakis(2,3-di-O-acetyl-6-O-sulfo)-β-cyclodextrin (HSβCD) in fused-silica capillaries utilizing a novel film forming device. HSβCD was used as a chiral selector whilst DVB was employed as the polymer crosslinker. Elemental analysis and FTIR spectral analysis of the bulk polymer showed that the HSβCD was incorporated into the polymer matrix. Optimisation of the enantioseparation conditions were investigated for a variety of parameters, including buffer pH and concentration of the organic solvent in the background electrolyte. Scanning electron microscopy (SEM) images showed that the chiral PLOT capillary morphology has the features of a continuous open path polymeric matrix. Capillary column-to-column migration time reproducibility showed RSD values of ≤ 4.0%. Separations of racemic mixtures of optically active amino acids were evaluated with these new chiral capillary columns. It was observed that D-enantiomers of aromatic amino acids migrated faster than the L-enantiomers. Using PLOT capillaries (50 μm i.d. and 365 μm o.d.), chiral separations could be very reliably performed with a 30/70 (v/v) % acetonitrile/phosphate buffer (pH 8.5, 100 mM) and an applied voltage of 20 kV.

The above study thus further documents the utility of PLOT CEC systems in the analysis of chiral compounds.