Origin of peak asymmetry and the effect of temperature on solute retention in enantiomer separations on imprinted chiral stationary phases

摘要: Abstract In enantiomer separations of d - and l -phenylalanine anlilide ( d,l -PA) on -PA-imprinted chiral stationary phases (CSPs), the use an aqueous buffer-organic solvent mixture as mobile phase resulted in improved column efficiency compared with what has previously been observed using containing acetic acid modifier. The dependence chromatographic parameters flow-rate sample load was studied. A strong asymmetry factor s ) -form a weak indicate that non-linear adsorption isotherm is main reason for broad peaks this system. Depending method used preparation materials, different shapes plots retention selectivity versus were obtained, indicating differences site distribution between polymers. slow mass transfer still present but agreement results from other ion-exchange or large porous particles. band widths both enantiomers showed similar temperature, which contrast to earlier reports imprinted polymers reversible covalent bonding separation. As expected these results, separation (α) capacity k ′) no only flow-rate. study effect temperature selectivity, linear Van 't Hoff obtained giving ΔH ΔS ′ values (binding -PA, absolute apparent -form) ΔΔH app ΔΔS (differential binding exothermic process. Changing pH 7 4 increase, mainly . Using acid-containing mixture, endothermic process positive , values. interpreted terms extensive solvation solute ammonium groups, being most pronounced phase.