Kinetic Study of Interaction between Solute Molecule and Surfactant Micelle

Abstract

We developed moment analysis of affinity kinetics by chromatographic capillary electrophoresis (MKCCE) method for the kinetic study of intermolecular interactions. Association and dissociation rate constants of the interaction in a micellar electrokinetic chromatography (MEKC) system between thymol and sodium dodecylsulfate micelle were determined by the MKCCE method. It is a method based on the moment theory for the kinetic study of intermolecular interactions under the conditions that neither immobilization nor chemical modification of molecules is required. In CCE mode, experimental conditions are controlled so that the migration of solute-micelle complex is stopped and only solute molecules migrate in a capillary. Mass transfer behavior of solute molecules in the CCE system is analogous to that in a chromatographic system. However, because it was difficult in practice to really perform CE experiments under the CCE conditions, CE data were measured with changing experimental conditions, i.e., applied pressure, under the conditions that the migration velocity of solute-micelle complex was around zero. The rate constants could be analytically determined from the CE data. In the MKCCE method, it is not necessary to fit elution curves numerically calculated to those experimentally measured for the determination of the rate constants. Regarding the interaction between thymol and SDS micelles, association equilibrium constant and association and dissociation rate constants were determined as 6.35 × 10 3 dm 3 mol -1 , 5.6 × 10 4 dm 3 mol -1 s -1 , and 8.7 s -1 , respectively. It was demonstrated that the MKCCE method was effective for the kinetic study of intermolecular interactions.

Moment theory for the analytical determination of rate constants for solute permeation at the interface of spherical molecular aggregates

“…Moment analysis is one strategy to extract information about chemical equilibrium, mass transfer rates, and reaction kinetics from experimentally measured elution peak profiles [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. In this study, moment equations were developed to analytically determine k in and k out from the elution peak profiles measured in EKC systems ( Fig.…”

Moment Analysis of Mass Transfer Kinetics in Micellar Electrokinetic Chromatography Systems

“…For example, although the cmc of SDS is reported as 8.1 × 10 -3 mol dm -3 in water, 1,5 it was measured as 2.1 × 10 -3 mol dm -3 in the running buffer solvent, which contained phosphate salt and methanol, in a previous study. 7,22 The curved profiles at kin = 1.5 × 10 -6 m s -1 indicate that the values of kin and kout were accurately determined at Cm = 2.7 × 10 -4 mol dm -3 because the contribution of the kint-term is sufficiently larger than that of the DL-term in Fig. 7.…”

“…However, as explained earlier, we have practically measured CE data while changing the applied pressure to the capillary, because it was hard to actually conduct MEKC experiments under the CCE conditions. 7,21,22 The values of μ1 and μ2′ of the elution peaks, which had to be measured under the CCE conditions, were estimated by analyzing the CE data by a successive approximation method. An appropriate applied pressure, of which direction is opposite to that of electroosmotic flow (EOF), must be added to the capillary under the CCE conditions.…”

“…For example, the values of ka and kd were determined in an inclusion complex formation system, i.e., between thymol and sulfated-β-cyclodextrin, 21 and in a MEKC system using surfactant micelles, i.e., between thymol and SDS micelle. 22 Neither immobilization nor chemical modification, e.g., fluorescence labelling, of the solute and ligand molecules is required in the MA-CCE method. This is a preliminary study for the quantitative determination of kin and kout of the interfacial permeation of solute molecules from elution peak profiles measured by CCE.…”

Moment Analysis Theory for Size Exclusion Capillary Electrochromatography with Chemical Reaction of Intermolecular Interaction

“…Both the equilibrium and kinetic information about intermolecular interactions can be analytically obtained from the μ1 and μ2′ values of elution peaks by the MA theory. 10,11 In this study, as a first step, new moment equations were developed for analyzing some mass transfer phenomena and intermolecular interactions in the SECEC system, in which the association and dissociation reactions of Eq. (1) simultaneously took place.…”