[Extra-thermodynamic properties of 2-arylpropionic acids on a chiral-AGP column by high performance liquid...

The effect of temperature (274-313 K) on the chromatographic behavior of naproxen and ibuprofen on a Chiral-AGP column was investigated with a mobile phase consisting of 50 mmol/L phosphate buffer (pH 6.41) and 0.5% (or 1.0%, v/v) 1-propanol. Higher temperature was found disadvantageous to the enantiomeric separation. With temperature increased, the retention time, resolution and selectivity of the chiral separation were decreased. The resolution of naproxen was larger than that of ibuprofen in all cases. When naproxen and ibuprofen enantiomers were entirely separated by the mobile phase containing 1.0% 1-propanol, the maximum temperatures allowed were 298 K and 288 K, respectively. All of the Van' t Hoff plots of the In k vsrsus 1/T were found to have good linearity, with the correlation coefficients better than 0.99 in all cases. The thermodynamic parameters (changes of enthalpy, i. e., deltaH0, for the transfer of enantiomers from the mobile phase to the stationary phase and differences of enthalpy and entropy changes, i. e., deltaS,R deltaH0 and deltaS,R deltaS0) were calculated. In general, in the temperature range examined the enthalpic contribution to the overall enantiomer transfer energy was found to be more significant than the entropic one.