Sodium Dodecyl Sulfate Micellar System Research Articles

Separation of nucleotides using micellar electrokinetic capillary chromatography

The effect of the pH of the background electrolyte and its ionic strength, via Good's buffers, in capillary zone electrophoresis (CZE) on the separation of mono-, di-, triphosphate, adenosine cyclic- monophosphate nucleosides and adenine was investigated. Micellar electrokinetic capillary chromatography (MEKCC) using a cationic surfactant such as dodecyltrimethylammonium bromide offers better separation and shorter analysis than the sodium dodecyl sulfate micellar system. Extension of the elution range could be performed by decreasing the pH and efficiency was improved by adding ethylenediaminetetraacetic acid to the mixture sample reaching 130 000 and 60 000 theoretical plates for c-AMP and GDP, respectively.

Study of the Polarity and Hydrogen-Bond Ability of Dodecyltrimethylammonium Bromide Micelles by the Kamlet−Taft Solvatochromic Comparison Method

We have studied the dipolarity/polarizability (π*), hydrogen-bond donor acidity (α), and hydrogen-bond acceptor basicity (β) of dodecyltrimethylammonium bromide (DTAB) micelles using the Kamlet−Taft solvatochromic comparison method. DTAB micelles were found to be quite polar (π* = 1.02), to have relatively strong hydrogen-bond donating ability (α = 0.700), and to have moderate hydrogen bond accepting ability (β = 0.486). These values are compared to the π*-, α-, and β-values of sodium dodecyl sulfate (SDS) micelles obtained in a previous solvatochromic study and are found to be qualitatively consistent with linear solvation energy relationship studies of both SDS and DTAB micellar systems. The chemical interpretation of these parameters and the nature of DTAB micelles which they reflect are discussed. By comparison to the solvatochromic parameters of representative pure solvents such as DMSO (π = 1.00), 2-propanol (α = 0.69), and ethylbenzoate (β = 0.43), it is evident that the micellar environments obser...

Migration behaviour of micelle counterions in micellar electrokinetic chromatography: influence on micelle mobility, efficiency and selectivity

The migration behaviour of micelle counterions in micellar electrokinetic chromatography (MEKC) is treated theoretically. It is demonstrated that, due to a high degree of counterion binding, micelle counterions in commonly used surfactant systems possess negative transport numbers under MEKC conditions. This phenomenon is illustrated for a sodium dodecyl sulphate micellar system in which sodium ions possess a negative effective mobility. In addition to that, the influence of sodium and tris(hydroxymethyl)aminomethane as dodecyl sulphate counterions on the effective mobility of micelles, efficiency and selectivity in MEKC analyses is evaluated.

Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

Migration of charged compounds in micellar electrokinetic chromatography (MEKC) is based on micellar solubilization as well as electrophoretic migration. Consequently, the migration behaviour of these compounds can be described with a retention model or a mobility model. Both models are discussed and evaluated for the migration behaviour of monovalent weak acids in a sodium dodecyl sulphate micellar system. We have shown that the calculation of retention factors may be troublesome for hydrophobic compounds, due to interaction with surfactant molecules in the aqueous phase. Therefore, the mobility model is preferable. The simultaneous determination of dissociation constants by spectroscopic and electrophoretic methods is discussed and apparent dissociation constants in micellar media are determined, showing that p K a shifts may occur in MEKC analyses, due to micellar solubilization. Furthermore, a sample stacking procedure is described, based on differences in overall effective mobilities between aqueous and micellar electrolyte systems.

Accelerated Diels–Alder reaction of quinones generated in situ by a modified electrode in an aqueous sodium dodecyl sulfate micellar system

K. Chiba, M. Jinno, A. Nozaki and M. Tada, Chem. Commun., 1997, 1403 DOI: 10.1039/A703113K

Hydrogen-bonding interaction-assisted micellar electrokinetic chromatography using mixed surfactant systems

Micellar electrokinetic chromatography was examined using mixed surfactant systems consisting of Brij 35 or Tween 20, non-ionic surfactants with a polyether structure, together with sodium dodecyl sulfate (SDS). Addition of the non-ionic surfactant to a SDS micellar system provides a selective increase in the relative capacity factors of some substituted benzenes having hydrogen-donating substituents such as a hydroxyl, amino and amide groups. This effect can be ascribed to hydrogen bond formation between these solutes and the polyether segments of the non-ionic surfactant. The hydrogen-bonding interaction appears to work additively against the hydrophobic interaction. The separation selectivity can be well controlled by adjusting the mixing ratio of the two surfactants. The thermodynamic aspects of the mixed micellar system are discussed in detail.

Study of the Polarity and Hydrogen Bond Ability of Sodium Dodecyl Sulfate Micelles by the Kamlet−Taft Solvatochromic Comparison Method

We have studied the dipolarity/polarizability (π*), hydrogen bond donor acidity (α), and hydrogen bond acceptor basicity (β) of sodium dodecyl sulfate (SDS) micelles using the Kamlet−Taft solvatochromic comparison method. The micellar environments of solubilized indicator molecules are quite polar (π* = 1.06) and have strong hydrogen bond donating ability (α = 0.87) and moderate hydrogen bond accepting ability (β = 0.40). Both the high dipolarity and especially the strong hydrogen bond acidity support previous work that indicates water is present in the indicators' micellar microenvironments. In contrast to many previous UV−vis spectroscopic studies of the polarity of SDS micelles, we have resolved the recorded micellar spectra so as to obtain the micellar spectrum of the indicators free from contributions of the indicator in the accompanying aqueous phase. This study was conducted to rationalize and complement linear solvation energy relationship (LSER) studies of partitioning in SDS micellar systems which have recently appeared in the literature. To our knowledge this is the first study in which curve resolution is applied to micellar spectra for the purpose of characterizing both the polarity and hydrogen bond ability of SDS micelles.

Evaluation of Solute Hydrophobicity by Microemulsion Electrokinetic Chromatography

Microemulsion electrokinetic chromatography (MEEKC) was introduced to evaluate the hydrophobicity of various kinnds of compounds. Using a separation solution consisting of sodium dodecyl sulfate (SDS), 1-butanol, heptane, and a borate-phosphate buffer, the logarithm of the capacity factors, which is proportional to the free energy of transfer into the microemulsion, was high correlated with the logarithm of the octanoywater partition coefficients (log P ow ) rather than with that of the SDS micelle/water partition coefficients measured by micellar electrokinetic chromatography. Even for compounds with hydrogen bond accepting or donating sites, the correlation of the partition coefficients between the microemulsion and the octanoywater system was established without corrections for hydrogen bond effects. Reproducibilities of both run-to-run and batch-to-batch analyses were drastically improved by the use of the migration index concept, itch is analogous to the retention index concept. Furthermore, the thermodynamic behavior of partitioning into the microemulsion was examined. In both the enthalpy and the entropy terms of transfer, the microemulsion system was more similar to a phospholipid vesicle than the octanoywater and SDS micellar systems. Preliminary results of quantitative migration-activity relationship studies, which are defined as quantitative structure-activity relationship studies using the electrophoretic migration data of MEEKC, indicated that this hydrophobic parameter provided slightly better regression to the toxicity data of phenol derivatives than the conventional log P ow . MEEKC rill provide a biologically useful hydrophobic parameter with minimum samples, high reproducibility, wider range of measurement, high resolution, and a single, universal scale

Reassignment of 13C NMR peaks of SDS micellar system by HMQC-NMR spectroscopy

The 13C NMR chemical shifts of sodium dodecyl sulphate (SDS) were measured at high concentrations by two-dimensional heteronuclear multiple quantum correlation (HMQC) spectroscopy to give accurate assignments for various signals obtained in the 13C NMR spectra of an SDS aggregated system.