sodium-dodecyl-sulfate and formamide

The effect of formamide (FA) as a modifier on the retention in MEKC with SDS as the detergent was investigated. The mobility of a series of alkylphenones and of a zwitterionic fluorescent compound as a function of the FA and the SDS concentration was determined for this purpose. Buffering electrolyte was borate, pH 9.23, with total ionic strength of 50 mM. The dependence of the mobility on the FA content - up to 63% w/w - of the BGE (at 10 mM SDS) allows the conclusion that the micelles are destabilized, and the CMC is shifted to higher values. In the system containing 33% FA or more no micelles are present anymore, and the retention factors of all compounds tend to zero. In an MEKC system with 27% v/v FA the CMC of SDS is increased from 2.4 mM in the aqueous BGE with the same buffer composition to 9.7 mM, a behavior that is in contrast to electrolyte-free FA-water systems. The partition constants of free analytes and the formation constants of the adduct between analyte and detergent monomer (assuming 1:1 stoichiometry) were derived from the dependence of the mobility on the SDS concentration. In addition, the involved equilibria were extended by that from the distribution of the analyte-monomer adduct between aqueous and micellar phase, and the according partition constants were derived as well. A selective change in the extent of partitioning was observed for the zwitterionic compound. In general, all binding constants were decreased upon addition of FA, though to a different extent. Although the binding constants of the analyte-monomer associate were only slightly influenced, the most pronounced decrease is found for their partitioning into the micelles.

Topics: Buffers; Chromatography, Micellar Electrokinetic Capillary; Electrochemistry; Fluorescent Dyes; Formamides; Ketones; Micelles; Phenol; Sodium Dodecyl Sulfate; Water

The effect of the three different surfactants, sodium dodecyl sulfate (SDS), diethylhexyl sodium sulfosuccinate (AOT), and taurodexycholic acid sodium salt (STDC) on the nonaqueous capillary electrophoretic separations of hydrophobic compounds were compared with formamide containing 20 mM K2HPO4 as electrolyte solvent. Separations of all selected uncharged hydrophobic compounds, e.g., p-arylacetophones were shown to be strongly dependent on the kind of surfactant. The electrolyte containing 180 mM SDS provided the best result for the selected samples.

Topics: Acetophenones; Dimethylformamide; Dioctyl Sulfosuccinic Acid; Electrophoresis, Capillary; Formamides; Hydrophobic and Hydrophilic Interactions; Molecular Structure; Sodium Dodecyl Sulfate; Solvents; Succinates; Surface-Active Agents; Taurodeoxycholic Acid

Topics: Blotting, Southern; Formamides; Hot Temperature; Nucleic Acid Hybridization; Sodium Dodecyl Sulfate