Adsorption of proteins at the solution/air interface influenced by added nonionic surfactants at very low concentrations for both components. 3. Dilational surface rheology.

The influence of the addition of the nonionic surfactants C12DMPO, C14DMPO, C10OH, and C10EO5 at concentrations between 10(-5) and 10(-1) mmol/L to solutions of β-casein (BCS) and β-lactoglobulin (BLG) at a fixed concentration of 10(-5) mmol/L on the dilational surface rheology is studied. A maximum in the viscoelasticity modulus |E| occurs at very low surfactant concentrations (10(-4) to 10(-3) mmol/L) for mixtures of BCS with C12DMPO and C14DMPO and for mixtures of BLG with C10EO5, while for mixture of BCS with C10EO5 the value of |E| only slightly increased. The |E| values calculated with a recently developed model, which assumes changes in the interfacial molar area of the protein molecules due to the interaction with the surfactants, are in satisfactory agreement with experimental data.

Effect of water hardness on surface tension and dilational visco-elasticity of sodium dodecyl sulphate solutions.

The complementary drop and bubble profile analysis and maximum bubble pressure tensiometry are used to measure the dynamic surface tension of aqueous SDS solutions in the presence of hardness salts (CaCl(2) and MgCl(2) in the ratio of 2:1 at concentrations of 6 and 40FH). The presence of hardness salts results in an essential increase of the SDS adsorption activity, which indicates the formation of Ca(DS)(2) and Mg(DS)(2) in the SDS solutions. The surface tension isotherms of SDS in presence of Ca(DS)(2) and Mg(DS)(2) are described using the generalised Frumkin model.

Adsorption layer characteristics of mixed sodium dodecyl sulfate/C(n)EO(m) solutions 1. Dynamic and equilibrium surface tension.

Bubble profile analysis tensiometry is used to study the dynamic and equilibrium surface tensions of mixed sodium dodecyl sulfate (SDS)/C(12)EO(5) and SDS/C(14)EO(8) solutions. For the data analysis, a new theoretical model was employed, which assumes different adsorption mechanisms for each type of surfactants. In particular, the adsorption behavior of oxyethylated surfactants was described by the so-called reorientation model, which assumes two states of surfactant molecules with different molar areas in the surface layer, and additionally an intrinsic compressibility of the adsorbed layer.

Interfacial tensiometry as a novel methodology for the determination of surfactant adsorption at a liquid surface.

At low surfactant concentration the loss of molecules in the bulk phase due to adsorption can be significant if the surface-area-to-bulk-volume ratio is large. This loss of molecules, however, can be used to determine the adsorption of a surfactant if the experiments are performed under well-controlled conditions. Experiments are performed with the model surfactant tridecyldimethylphosphine oxide (C13DMPO) using drop profile analysis and ring tensiometry.

Dynamic surface tension and surface rheology of biological liquids.

The paper presents results of dynamic and equilibrium surface tension measurements (using a maximum bubble pressure instrument) of serum and urine samples that were obtained from 80 healthy human of various sexes and ages. These data were compared with surface tension measurements of biological liquids obtained from patients suffering from malignant neoplasm of corpus uteri (n=5) and cervix uteri (n=31). In addition, surface dilatational rheology was determined on 32 samples using a drop shape method.