Surfactants neutral loss

These results obtained from the analyses of industrial blends proved that the identification of the constituents of the different surfactant blends in the FIA-MS and MS-MS mode can be performed successfully in a time-saving manner only using the product ion scan carried out in mixture analysis mode. The applicability of positive ionisation either using FIA-MS for screening and MS-MS for the identification of these surfactants was evaluated after the blends examined before were mixed resulting in a complex surfactant mixture (cf. Fig. 2.5.7(a)). Identification of selected mixture constituents known to belong to the different blends used for mixture composition was performed by applying the whole spectrum of analytical techniques provided by MS-MS such as product ion, parent ion and/or neutral loss scans. 

The quantification of N-containing surfactants under MS-MS conditions but without standard addition resulted in a SD of 14%. In parallel, an increase in time by a factor of 1.5 was found compared with FIA-MS analysis without standard addition. The results obtained with MS-MS using product, parent or neutral loss scan are more... 

In a multiphase formulation, such as an oil-in-water emulsion, preservative molecules will distribute themselves in an unstable equilibrium between the bulk aqueous phase and (i) the oil phase by partition, (ii) the surfactant micelles by solubilization, (iii) polymeric suspending agents and other solutes by competitive displacement of water of solvation, (iv) particulate and container surfaces by adsorption and, (v) any microorganisms present. Generally, the overall preservative efficiency can be related to the small proportion of preservative molecules remaining unbound in the bulk aqueous phase, although as this becomes depleted some slow re-equilibration between the components can be anticipated. The loss of neutral molecules into oil and micellar phases may be favoured over ionized species, although considerable variation in distribution is found between different systems. 

The free carboxylic acid content of the membrane has not been analyzed but there is a sufficient amount to produce a mild anionic charge at neutral or alkaline pH levels. The membrane absorbs cationic dyes and the effect of cationic surfactants added to the feedwater is readily observed as a loss in flux. 

When a surfactant is adsorbed onto a solid surface, the resultant effect on the character of that surface will depend largely upon the dominant mechanism of adsorption. For a highly charged surface, if adsorption is a result of ion exchange, the electrical nature of the surface will not be altered significantly. If, on the other hand, ion pairing becomes important, the potential at the Stern layer will decrease until it is completely neutralized (see Fig. 9.5). In a dispersed system stabilized by electrostatic repulsion, such a reduction in surface potential will result in a loss of stability and eventual coagulation or flocculation of the particles (Chapter 10). 

Asymmetric epoxidation of terminal alkenes with hydrogen peroxide was optimized with electron-poor chiral Pt(II) complexes bearing a pentafluorophenyl residue, as described in Section 23.3.1.6. The same catal3rtic system was made more sustainable by the employment of water as the solvent under micellar conditions. Surfactant optimization revealed the preferential use of neutral species like Triton-XIOO to solubihze both the catalyst and substrates. In several cases an increase of the asymmetric induction was observed (Scheme 23.43). The use of an aqueous phase and the strong affinity of the catalyst for the micelle allowed the recycling of the catalytic system by means of phase separation and extraction of the reaction products using an apolar solvent (hexane). The aqueous phase containing the catalyst was reused for up to three cycles with no loss of activity or selectivity. 

Changing the solid surface jfrom positively charged alumina to silica, which is negatively charged at neutral pH, results in a complete loss of SDS adsorption [31]. The same behavior has been observed for dodecyl benzene sulfonate on silica [32]. This demonstrates clearly that surfactant adsorption depends on the nature of the solid surface. Further examples of the dramatic influence of surface nature on surfactant adsorption properties are widely documented in Chapter 3. Particular emphasis is placed on surfactant adsorption on nonpolar solid surfaces. 

Larin and Gallimore [86] have provided evidence to show that if viral protein is solubilized by surfactants this may result in loss or enhancement of specific viral antigenicity. Treatment of influenza virus with Triton X-100 significantly enhances the antigenicity of viral protein as judged by virus neutralization and haemagglutination inhibition tests similar treatment by Tween 80, NaDS and deoxycholate led to a partial or complete loss of immunogenicity. 

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