COSMO-RS for the prediction of the retention behavior in micellar liquid chromatography based on partition coefficients of non-dissociated and dissociated solutes

Mehling, Tanja; Kloss, Linda; Mushardt, Heike; Ingram, Thomas; Смирнова, Ирина

doi:10.1016/j.chroma.2012.11.079

Cited by 10 publications

(12 citation statements)

References 44 publications

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“…In this work, all partition coefficients were measured only once. However, the MLC technique has been established for the determination of partition coefficients of neutral molecules and we used the same method and retention model as described in our previous publications. , Therefore, the maximum error is assumed to be Δlog K i = ± 0.25 in accordance with our previous experiments. The experimentally obtained and calculated partition coefficients in the system TX-114/SDS are shown in Table .…”

Section: Results and Discussionmentioning

confidence: 99%

“…Partition coefficients in mixed surfactant systems (an equimolar solution of TX-114/SDS and TX-114/CTAB) were determined using micellar liquid chromatography. In our previous studies, ,, the MLC technique was successfully applied to the determination of partition coefficients in various micelles. Chromatographic analysis was performed with an Agilent 1200 series HPLC.…”

Section: Methodsmentioning

confidence: 99%

“…In the case of dissociated solutes, the evaluation with MLC is difficult because of the very strong binding at higher CTAB content, designated as overbinding. 21,38,39 The prediction of partition equilibria of charged molecules in micellar systems is also challenging. There is a lack of theoretical methods to predict the partition behavior of ionized solutes in mixed micelles.…”

Section: Introductionmentioning

confidence: 99%

“…It could be demonstrated that partition coefficients of both the neutral and dissociated form increase with increasing CTAB content as a result of enhanced electrostatic interactions. In the case of dissociated solutes, the evaluation with MLC is difficult because of the very strong binding at higher CTAB content, designated as overbinding. ,, The prediction of partition equilibria of charged molecules in micellar systems is also challenging. There is a lack of theoretical methods to predict the partition behavior of ionized solutes in mixed micelles.…”

Section: Introductionmentioning

confidence: 99%

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Micellization and Partition Equilibria in Mixed Nonionic/Ionic Micellar Systems: Predictions with Molecular Models

et al. 2017

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In practical applications, surfactant solutions are mostly used in mixtures of nonionic and ionic surfactants because they have improved characteristics compared to those of single surfactant solutions. By adjusting the composition of the micelles and the pH value, the solubilization of solutes can be enhanced. Nevertheless, the partitioning of solutes between nonionic/ionic mixed micelles and the aqueous phase is studied to a much lesser extent than for single surfactant solutions. Theoretical methods to predict partition equilibria in mixed micelles are of interest for screening studies. For those, the composition of the mixed micelle has to be known. Here we investigate mixtures of TX-114 (Triton X-114), Brij35 (C12E23), SDS (sodium dodecyl sulfate), and CTAB (cetyltrimethylammonium bromide). First, to investigate the surfactant compositions in the micelles, molecular dynamics (MD) self-assembly simulations were applied. Thereafter, the predictive COSMO-RS model, which applies the pseudophase approach, and its extension to anisotropic systems termed COSMOmic were compared for the prediction of partition equilibria in mixed micelles, where various molar ratios of the surfactants were considered. It could be demonstrated that both methods are applicable and lead to reasonable predictions for neutral molecules. However, taking into account the three-dimensional structure of the micelle is beneficial because the calculations with COSMOmic are in better agreement with experimental results. Because the partitioning behavior of ionizable molecules in mixed micelles is of particular interest, the partitioning of ionized isovanillin in mixed Brij35/CTAB micelles at different micelle compositions was calculated with COSMOmic. Using a thermodynamic cycle, the position-dependent pK of isovanillin within the micelle is calculated on the basis of COSMOmic free energy profiles. As a result, the protolytic equilibrium of isovanillin within the micelles can be taken into account, which is crucial for the reliable prediction of partition coefficients.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Micellization and Partition Equilibria in Mixed Nonionic/Ionic Micellar Systems: Predictions with Molecular Models

et al. 2017

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“…Similar effects were observed in previous studies. 28,84 According to the protolytic equilibrium at pH = 10.5 the second dissociable functional group (hydroxyl group) of 4-hydroxybenzoic acid and phloretic acid is also dissociated. Because of increasing net charge of the solutes at higher pH, increasing attraction forces between the cationic groups of CTAB and the dissociated molecules are expected.…”

Section: Methodsmentioning

confidence: 99%

Solute Partitioning in Micelles: Combining Molecular Dynamics Simulations, COSMOmic, and Experiments

et al. 2017

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The partition equilibria of solutes between micelles and an aqueous phase is a key factor in many applications. Depending on the task, many micelle-solute combinations are possible. Therefore, theoretical methods to predict the partition behavior in micellar systems are needed. Here, two predictive methods are evaluated and compared. First, it is shown how molecular dynamics simulations (MD) with the umbrella sampling method can be used to calculate free energy profiles in micellar systems. The second applied method is an extension of the COSMO-RS theory to anisotropic systems termed COSMOmic. Both methods are compared by means of free energy profiles and experimental micelle/water partition coefficients. A particular focus is on the partitioning of ionized solutes. As experimental data for partitioning in micelles especially for charged solutes is rare, partition coefficients were also determined experimentally. To get a general understanding of micelles examples of all micelle classes (classified by headgroup charge) are studied: nonionic Triton X-114 (TX114), zwitterionic miltefosine (HePC), anionic sodium dodecyl sulfate (SDS), and cationic cetyltrimethylammonium bromid (CTAB). The free energy profiles of neutral solutes obtained from MD simulations and COSMOmic are in an overall good agreement, and partition coefficients from both methods are in good agreement with experimental data. Depending on the system, the results for charged solutes show some deviations between the methods and experimental data.

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Partition coefficients of ionizable solutes in aqueous micellar two-phase systems

Ingram

Mehling

Смирнова

2013

Chemical Engineering Journal

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COSMO-RS for the prediction of the retention behavior in micellar liquid chromatography based on partition coefficients of non-dissociated and dissociated solutes

Cited by 10 publications

References 44 publications

Micellization and Partition Equilibria in Mixed Nonionic/Ionic Micellar Systems: Predictions with Molecular Models

Micellization and Partition Equilibria in Mixed Nonionic/Ionic Micellar Systems: Predictions with Molecular Models

Solute Partitioning in Micelles: Combining Molecular Dynamics Simulations, COSMOmic, and Experiments

Partition coefficients of ionizable solutes in aqueous micellar two-phase systems

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