A dynamic molecular probe to investigate catalytic effects and Joule heating in enantioselective MEKC

Abstract

Enantiomerization of ferroin [tris(1,10-phenanthroline)-iron (II)-complex] was investigated by enantioselective dynamic micellar EKC. The enantiomer separation was performed in an aqueous 50 mM sodium borate/sodium. dihydrogenphosphate buffer at pH 8.0 in the presence of the chiral surfactant sodium cholate. The unified equation of dynamic chromatography was employed to determine reaction rate constants from the electropherograms featured with distinct plateau formation. Activation parameters ΔH‡ = 124.0 ± 0.5 kJ/mol and ΔS‡ = 121 ± 1 J.K-1mol-1 were calculated from temperature-dependent measurements between 10.0 and 27.5°C in 2.5 K steps. Considering the data obtained by polarimetry of enantiomeric pure ferroin in water, it was found that enantiomerization rate in the micelle is accelerated by a factor of 12. Because of the highly positive activation entropy ΔS‡, ferroin was used as a temperature-sensitive dynamic molecular probe to determine temperature deviations caused by Joule heating. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.