Rate constant determination of interconverting enantiomers by chiralchromatography using a stochastic model

It may happen under the conditions employed that enantiomers interconvert to each other. In this case,obviously, the kinetics of the process is to be examined. When enantiomers dynamically interconvert toeach other during the separation process, a plateau is observed between the adjacent peaks (so-calledBatman peak appears). The peak shape depends on the rate constant of this dynamic reaction.A novel stochastic model was derived which takes both the separation and the interconversion intoaccount at the molecular level – thus the effects of the parameters affecting the separation can be investi-gated. The novel model was used for the study of quetiapine, a drug molecule that interconverts during theseparation to evaluate the rate constant based on the enantiomerization. Various flow rates and tempera-tures were used, and good agreement was obtained with the rate constant obtained from optical rotationexperiments and with the software written by Trapp [1]. The most important result we concluded is theneed of mild conditions during the separation to ascertain the rate constant the most accurately (lowflow rates and temperatures where the enantiomerization process is limited to a few interconversions).The comparison of the rate constants of the on-column and the off-column experiments should be doneby considering the stationary phase effects that are absent in the off-column experiments