Surfactants determination

The method of the analysis of the CS described in the international standai d ASTM (D 820 - 93) is a long time, multi-stage procedure. Accuracy of AIST determination is low, since surfactants determined by an indirect method of subtraction. Thus, the objective of our research was to develop an exact and express method of AIST determination in CS. 

Actually, the successful use of cationic surfactants (cSurf), as flotation reagents, frothers, metal corrosion inhibitors, pharmaceutical products, cosmetic materials, stimulates considerable increase in their production and as a result increases their content in natural water. As cationic surfactants are toxic pollutants in natural water and their maximum contaminant level (MCL) of natural water is 0.15-4.0 mg/dm, it is necessary to use methods for which provide rapid and reliable determination with sensitivity equal to at least 0.1 of MCL. Practically most sensitive methods of cationic surfactant determination include the preconcentration by extraction or sorption. Analytical methods without using organic solvents are more preferable due to their ecological safety. 

The investigation leads to the elaboration of solid-phase spectrophotometric and test methods of different cationic surfactants determination in water. The detection limits of cationic surfactants with hydrocarbon radical length is 0.7 mg/dm, is 0.2 mg/dm, C is 0.009 mg/dm and is 0.003 mg/dm by using a 100 cm sample. Metrological performance of method was examined on the natural samples. Proposed method is highly sensitive, simple, rapid and guarantees ecological purity of analysis. 

Partition coefficients of different surfactants, determined in the laboratory, for various environmental matrices... 

Wang, L.K. Cationic Surfactant Determination Using Alternate Organic Solvent, PB86-194164/ AS US Department of Commerce, National Technical Information Service Springfield, VA, 1983 ... 

Nomura Y, Ikebukuro K, Yokoyama K, Takeuchi T, Arikawa Y, Ohno S, Karube I (1994) A novel microbial sensor for anionic surfactant determination. Anal Lett 27 3095 - 3108... 

Non-ideal solution theory is used to calculate the value of a parameter, S, that measures the interaction between two surfactants in mixed monolayer or mixed micelle formation. The value of this parameter, together with the values of relevant properties of the individual, pure surfactants, determines whether synergism will exist in a mixture of two surfactants in aqueous solution. 

In general, surface activity behaviour in food colloids is dominated by the proteins and the low-molecular-weight surfactants. The competition between proteins and surfactants determines the composition and properties of adsorbed layers at oil-water and air-water interfaces. In the case of mixtures of proteins with non-surface-active polysaccharides, the resulting surface-activity is usually attributed to the adsorption of protein-polysaccharide complexes. By understanding relationships between the protein-protein, protein-surfactant and protein-polysaccharide interactions and the properties of the resulting adsorbed layers, we can aim to... 

With hydrophilics, control of cell opening is accomplished by the use of surfactants. Catalysts are rarely needed or used. The reason goes to the tradition of using hydrophilic polyurethane for the most part in medical devices and agricultural products where catalysts are unacceptable. A broader range of surfactants can be used in work with hydrophilic polyurethanes, and the surfactants determine cell structure. Table 3.4 shows the effects of surfactants. 

Even though the adsorption of SOS, SDBS, and SOBS was performed in the same way as described above, only the solids obtained at two surfactant concentrations, according to their respective CMC were analysed by SEM. Table 1 shows the concentrations utilised as well as the corresponding CMC for these surfactants determined by conductance measurements. 

Sanchez-Martinez, M.L., M.P. Aguilar-Caballos, S.A. Eremin, et al. 2007. Long-wavelength fluorescence polarization immunoassay for surfactant determination. Talanta 72 243-248. 

FIGURE 31.8 Protein damage potential of a number of surfactants determined using the zein dissolution test. Higher the zein dissolution, higher is the damage potential of the surfactant. 

Schmidt, G. (1990) Silicone surfactants. Tenside Surfactants Determinants, 27, 324. 

Table 3.10 presents the values of Ce ,cr for some of the most employed surfactants determined by microscopic and macroscopic techniques. 

Foam stabilising properties of surfactants determined by Foam Pressure... 

Micellar media have been extensively used to affect rates of numerous organic and inorganic reactions.16-21 Catalysis or inhibition of solubilized species involve many kinds of interactions and may vary with the nature of the surfactant. The kinetic studies performed so far in solutions of micelle-forming surfactants can be grouped into two categories the first includes those cases in which a surfactant micelle acts only as a medium for the reaction, and the second includes reactions in which the surfactant participates directly either as a catalyst or as a substrate. This feature of surfactants determines their usefulness in practical processes. 

E. Rodenas-Torralba, B.F. Reis, A. Morales-Rubio, M. de la Guardia, An environmentally friendly multicommutated alternative to the reference method for anionic surfactant determination in water, Talanta 66 (2005) 591. 

Due to micelle formation the total surfactant concentration undergoes an abrupt increase. Since true (molecular) solubility of surfactants, determined by the CMC, remains essentially constant, an increased surfactant concentration in solution is caused by an increase in a number of formed micelles. Micellar solubility increases with increase in temperature, and thus a continuous transition from pure solvent and true solution to micellar solution, and further to different liquid crystalline systems and swollen surfactant crystals (see below), may take place in the vicinity of the Krafft point. 

The structure of surfactants determines considerably their behaviour at the interface between two immiscible liquids which differ considerably in their polarity. In practice, water or an aqueous electrolyte solution are most frequently considered as a polar phase, and hydrocarbons or their mixtures, e.g. oil fractions, as an apolar phase. In this connection, substances practically completely soluble in water are ascribed to the so-called water-soluble surfactants . Typical anionics are, depending on the polar group type, alkali metal salts, with a hydrocarbon tail of a length of C 2—C 8 Magnesium salts of alkyl ethoxysulphates are also partly soluble. Bivalent and trivalent metal derivatives of the same anionics are typically ascribed to oil-soluble surfactants. 

Samples Trace constituents Collector precipitates pH Surfactants Determination ... 

Attempt of correlating the molecular structures and experimental data, for example, cmc, and the thermodynamic parameters of micellization (enthalpy, entropy, and free energy), rests on the assumption that they have been calculated by a consistent procedure this point needs further consideration. At the outset, it should be noticed that there are systematic differences between the results, for example, the cmc, obtained by using distinct experimental techniques. The reason is that the function plotted (absorbance of micelle-solubilized dye, conductivity, surface tension, light scattering intensity, etc.) versus [surfactant] measures different averages of the various species in solution. Examples are surface tension that primarily depends on monomer concentration and solubilization of (water-insoluble) dye that depends mainly on the total amount of micelles present. The consequence is that cmc measured from surface tension will always be lower than cmc measured by dye solubilization [28]. In fact, values of the cmc of the same surfactant, determined by different groups, by the same technique show differences. For example, fifty-four erne s determined by the same technique for Cj NMe Br (measurements at 25°C) differ by 22% [29]. 

Testing of Surfactants. Determination of foaming power Modified Ross-Miles method, DIN 53902, Sheet 2, January 1971. 

The type of the polymer and surfactant determines their adsorptions degree. Langmuirs law can represent the relation between adsorbed polymer/surfactant concentration in the solution [1] ... 

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