Characterization of the Solvation Properties of Sodium n-Dodecyl Sulfate Micelles in Buffered and Unbuffered Aqueous Phases by Solvatochromic Indicators

Abstract

The solvation properties of a micellar electrokinetic chromatography (MEKC) system composed of an aqueous phosphate buffer at pH 7.0 and sodium n-dodecyl sulfate (SDS) have been determined with solvatochromic indicators and compared with those of pure unbuffered water−SDS micellar system. The solvatochromic measurements allow calculation of the critical micellar concentrations (CMC), partition coefficients for the test compounds, and solvation properties of the two micellar systems studied. The results obtained are in good agreement with data obtained here and in previous works from MEKC measurements for the phosphate−SDS system. The solvent properties and partition coefficients in phosphate−SDS buffer are very similar to those obtained in water−SDS system, but the CMC values are lower in the phosphate buffer. The obtained results indicate that SDS micelles are very polar (π* = 1.02±0.01), quite hydrogen-bond donor (HBD) acidic (α = 0.80±0.02), and moderately hydrogen-bond acceptor (HBA) basic (β = 0.62±0.01).

Microchip electrophoresis with electrochemical detection for the determination of analytes in the dopamine metabolic pathway

“…With the low SDS concentrations in this system, dopamine comigrated with other analytes of interest. However, if the SDS concentration was increased to concentrations above the critical micellar concentration , the positively charged dopamine interacted electrostatically with the negatively charged SDS micelles, causing it to migrate later (Fig. A).…”

Prediction of Partition Coefficients in SDS Micelles by DFT Calculations

“…where P is the partition coefficient of a compound distributed between the micellar and the aqueous phase, ν is the partial molar volume of the surfactant [7], C T is the total concentration of surfactant, CMC is the critical micellar concentration and k is the MEKC retention factor of the test compound. CMC is obtained from conductimetric analysis [28].…”

“…The partition coefficient of molecules in a system of micelles can be experimentally obtained by chromatographic techniques such as micellar electrokinetic chromatography (MEKC) [5][6][7]. From a computational point of view, the prediction of logP in systems of micelles could be performed by using molecular structures of micelles obtained by dynamic simulations (MDs) [8].…”

Continuous micellar electrokinetic focusing of neutral species driven by ion concentration polarization

“…In comparison to SDS, the lower extraction efficiency can be explained by the lower mobility of SC micelles leading to poorer repulsion at the IDZ. [30][31][32] Additionally, several physical and chemical parameters such as polarity and the ability to donate or accept hydrogen bonds influences the solvation properties of surfactants, and thus will ultimately impact the neutral species extraction efficiency by ICP. 31,32 PAHs found in soil and water pose a serious threat to human health and to water-dwelling species.…”