Fast and precise access to enantiomerization rate constants in dynamic chromatography

An analytical solution of the unified equation to evaluate elution profiles of interconverting enantiomers in dynamic chromatography is presented. Rate constants k 1 and k −1 and Gibbs activation energies are directly obtained from the chromatographic parameters (retention times t   R Aand t   R Aof the interconverting enantiomers, the peak widths at half height w A and w B , and the relative plateau height h p ), and the initial amounts A 0 and B 0 of the enantiomers without any iterative and time consuming computational step. Therefore, this equation is no longer limited to racemic analytes. The analytical solution presented here was validated by comparison with a dataset of 125,000 simulated elution profiles of enantiomerizations. Furthermore, it was found that the recovery rate from a defined dataset is on average 40% higher using the unified equation compared to evaluation methods based on iterative computer simulation. The new equation was applied to determine the enantiomerization rate constant of 1‐ n ‐butyl‐2‐ tert ‐butyldiaziridine by enantioselective gas chromatography. The activation parameters (Δ H ‡ = 112.6 ± 2.5 kJ/mol and Δ S ‡ = −27 ± 2 J/(K mol) were obtained from temperature‐dependent measurements between 100°C and 140°C in 10K steps. Chirality 18:489–497, 2006. © 2006 Wiley‐Liss, Inc.