The adsorption properties of short chain alcohols and Triton X-100 mixtures at the water–air interface

Modification of adsorption, aggregation and wetting properties of surfactants by short chain alcohols

The adsorption of methanol, ethanol and propan-1-ol at the solution-air and solid-solution interfaces, their aggregation in the aqueous media as well as wetting properties regarding their applications as additives or co-surfactants in the surfactants aqueous solution were discussed based on the literature data. Mutual influence of alcohols and surfactants on the solution-air and solid-solution interface tension was considered. For this purpose there were used different methods allowing to describe or predict changes of water surface tension as a function of alcohols concentration. These, in turn, as a function of alcohol and/or surfactant concentration were also analyzed by means of the methods applied for prediction of surface tension of aqueous solution of the classical surfactants mixture. The same considerations related to the behaviour of alcohol and surfactant at the solid-solution and solution-air interfaces were made. To explain the behaviour of alcohols and surfactants mixture at the solution-air and solid-solution interfaces the components and parameters of water, alcohols, surfactants and solids surface tension as well as the Gibbs free energy changes during the adsorption process were taken into account. It was proved that wettability of some solids can be predicted based on alcohol and surfactants adsorption as well as surface tension components and parameters. As follows the mutual influence of alcohol and surfactant on their adsorption at the solution-air and solid-solution interfaces as well as on the wetting properties at the alcohol concentration from zero to its critical aggregation concentration (CAC) is different from that at its concentration higher than CAC.

Volumetric and Surface Properties of Short Chain Alcohols in Aqueous Solution-Air Systems at 293 K

From measurements of the surface tension, density, viscosity and light scattering of aqueous solutions of methanol, ethanol and propanol at 293 K, their activity in the surface monolayer, surface excess concentration, and apparent and partial molar volume were determined. The surface excess concentration of alcohols at the water–air interface was determined from the Gibbs equation by using both the alcohol's activity and their molar fraction in the bulk phase and recalculated by using the Guggenheim–Adam equation. The values of the surface excess concentration determined from the Gibbs equation were also applied to determine the standard Gibbs energy of alcohol adsorption at the water–air interface from Langmuir’s equation and compared to those determined from that of Aronson and Rosen.

Effect of anionic surfactant and short-chain alcohol mixtures on adsorption at quartz/water and water/air interfaces and the wettability of quartz

Measurements of the advancing contact angles for aqueous solutions of sodium dodecyl sulfate (SDDS) or sodium hexadecyl sulfonate (SHS) in mixtures with methanol, ethanol, or propanol on a quartz surface were carried out. On the basis of the obtained results and Young and Gibbs equations the critical surface tension of quartz wetting, the composition of the surface layer at the quartz-water interface, and the activity coefficients of the anionic surfactants and alcohols in this layer as well as the work of adhesion of aqueous solutions of anionic surfactant and alcohol mixtures to the quartz surface were determined. The analysis of the contact angle data showed that the wettability of quartz changed visibly only in the range of alcohol and anionic surfactant concentration at which these surface-active agents were present in the solution in the monomeric form. The analysis also showed that there was a linear dependence between the adhesion and the surface tension of aqueous solutions of anionic surfactant and alcohol mixtures. This dependence can be described by linear equations for which the constants depend on the anionic surfactant and alcohol concentrations. The slope of all linear dependence between adhesion and surface tension was positive. The critical surface tension of quartz wetting determined from this dependence by extrapolating the adhesion tension to the value equal to the surface tension (for contact angle equal zero) depends on the assumption whether the concentration of anionic surfactant or alcohol was constant. Its average value is equal to 29.95mN/m and it is considerably lower than the quartz surface tension. The positive slope of the adhesion-surface tension curves was explained by the possibility of the presence of liquid vapor film beyond the solution drop which settled on the quartz surface and the adsorption of surface-active agents at the quartz/monolayer water film-water interface. This conclusion was confirmed by the work of adhesion of aqueous solutions of anionic surfactants and short-chain alcohol mixtures to the quartz surface determined on the basis of the contact angle data and molar fraction of anionic surfactants and alcohols and their activity coefficient in the surface layer.

Using buffer additives to improve analyte stream stability in micro free flow electrophoresis

Micro free flow electrophoresis (microFFE) is a separation technique that continuously separates analyte streams as they travel through an electric field applied perpendicularly to the flow in a microdevice. Application of the technique has been limited by the generation of electrolysis bubbles at the electrodes, which results in unstable flow paths through the device. The current paper introduces the use of surfactants and nonaqueous solvents in the carrier buffer as a means of increasing stability of separated analyte streams. Adding surfactant or nonaqueous solvents lowers the surface tension of the carrier buffer, which we hypothesize promotes the formation of smaller electrolysis bubbles. A 6-fold improvement in the standard deviation of analyte stream position was observed upon addition of 10 mM SDS. Likewise, an approximately 12-fold improvement in stability was observed upon addition of 300 microM Triton X-100. Similar stability improvements were found in carrier buffers containing nonaqueous solvents. An 8-fold improvement in stability was found with a carrier buffer containing 50% methanol and a 6-fold improvement was found with a carrier buffer containing 37.5% acetonitrile. Long term use was demonstrated with a carrier buffer containing 300 microM Triton X-100 in which separated analyte streams remained stable for nearly two hours.

Surface behavior of Triton X-165 and short chain alcohol mixtures

In this Article, the surface behavior of mixtures of nonionic Triton X-165 (TX-165) with methanol, ethanol, and propanol at constant Triton X-165 concentration in the range from 1 x 10(-7) to 10(-3) M in aqueous solutions was investigated by surface tension measurements of their solutions in a wide range of alcohol concentrations. The obtained values of the surface tension of solutions were compared with those calculated from Szyszkowski, Connors, and Fainerman and Miller equations. On the basis of the surface tension data, the Triton X-165 and alcohol concentrations at water-air interface and their standard free energy of adsorption as well as the composition of the monolayer at this interface were determined. Taking into account this composition and activity coefficient of Triton X-165 and alcohol, the free enthalpy of their mixing was also calculated. From the measurements and calculations, it results, among other things, that unexpectedly the Fainerman and Miller equation derived for ideal mixtures of homologous surfactant can be useful for the description of changes of the solution surface tension of the investigated mixtures and that the amount of short chain alcohols at the water-air interface at their low concentration in the bulk phase is proportional to the activity coefficient.