Surfactants classes

Tarazona A, Kreisig S, Koglin E and Schwuger M J 1997 Adsorption properties of two cationic surfactant classes on silver surfaces studied by means of SERS spectroscopy and ab initio calculations Prog. Colloid Polym. Sol. 103 181-92... 

The first two aspects entail relatively high concentrations of surfactants. In the last case, trace amounts are to be determined. When performing surfactant analysis, preconcentration and/or separation of the different surfactant classes are prerequisites for identifying and quantifying the compound in question. Furthermore, the trend is to analyze the individual components of any surfactant mixture. 

Thus, especially since the development of appropriately specific and sensitive analytical methods, as discussed in Chapter 2, it seems only logical that some highly water-soluble surfactants and their even more polar metabolites have been positively detected in potable water. In the following sections, examples are given according to the different surfactant classes as well as the source of the raw water used. 

Alkyl ether sulfates are/after alkyl benzene sulfonates(LAS),the group of technically important anionic surfactants with the largest production voluJne and product value. They have in comparison with other anionic surfactants special properties which are based on the particular structure of the molecule. These are expressed,for example,in the general adsorption properties at different interfaces, and in the Krafft-Point. Alkyl ether sulfates may be used under conditions, at which the utilization of other surfactant classes is very limited. They possess particularly favorable interfacial and application properties in mixtures with other surfactants. The paper gives a review of all important mechanisms of action and properties of interest for application. 

However, methods for predicting environmentally relevant properties of surfactants applicable for all surfactant classes are presently not available. Due to the absence of validated estimation methods, this chapter s goal is to supply information necessary to understanding the behavior of surfactants in the environment and to provide data on the relevant properties of surfactants. 

Many methods have been developed for the quantitative determination of each class of surfactants. The analysis of commercial surfactants is much more complicated since they may be comprised of a range of compounds within a given structural class, may contain surface-active impurities, may be formulated to contain several different surfactant classes, and may be dissolved in mixed organic solvents or complex aqueous salt solutions. Each of these components has the potential to interfere with a given analytical method so surfactant assays are sometimes preceded by surfactant separation techniques. Both the separation and assay techniques can be highly specific to a given surfactant/solution system. Table 3.4 shows some typical kinds of analysis methods that are applied to the different surfactant classes. 

Figure 14.4 Chromatograms of excipients in different classes. Plot (a) represents excipients in surfactant class. The curves from the bottom are blank, cremorphor 35, SLS, Tween 80 and VE, respectively. Plot (b) represents excipients in the filler class. The curves from the bottom are blank, DCP, lactose, mannitol, MCC and SWS, respectively. In both plots, the sample solvent and mobile phase used are 20% ACN-80% pH 2, 25 mM phosphate buffer and a gradient from 30% ACN-70% pH 2, 25 mM phosphate buffer to 80% ACN-20% pH 2, 25 mM phosphate buffer, respectively. The samples were injected at 1800 p,L onto a Zorbax SB-Cg, 4.6 x 150 mm, 3.5 xm column at 35°C with a flow rate of 1 mL/min. The detection was at 210 nm.

Fatty alcohols are one of the most useful intermediates for the production of nonionic surfactants, some of which are listed in Fig. 36.34. A detailed discussion on all the commercially available nonionic surfactants is beyond the scope of this work and only the major surfactant types are covered. A more complete discussion of different surfactant classes and their properties is available elsewhere.38... 

At 75 C (167 F), a representative U.S. Gulf Coast formation temperature, AES, AEGS, and AESo surfactant classes produced fairly stable foams in short-term tests (see Table I). Examination of these data indicated that the AEGS surfactants generally gave the... 

Procedures of these 40 C (104 F) experiments are described in the Experimental Section. Tests were performed at a representative west Texas formation temperature using a typical west Texas stock tank oil and a synthetic brine having a composition typical of west Texas injection waters. Results are summarized in Table III. The ratio of foam volume after 30 minutes at 40 C to that after 1 minute was used as an indication of foam stability. The surfactants which produced the greatest initial (1.0 minute) foam volumes also exhibited the greatest foam stability over the thirty minute test period. Because test temperature and salinity were different than used in earlier experiments, results in the presence of west Texas stock tank oil cannot be compared to results described above. However, trends in foam stability were consistent with those described above. Average stability of the foams produced by the AEGS and AES surfactant classes was greater than that of the AE foams. 

Non-ionics are second major surfactant class used in preparation and are manufactured in different forms. Non-ionic surfactants do not contain an ionisable group and have no electrical charge (Table 4.2). The most important non-ionic detergents TABLE 4.2... 

To understand the effects produced, it is necessary to distinguish between two classes of organic materials that markedly affect the CMCs of aqueous solutions surfactants class I, materials that affect the CMC by being incorporated into the micelle and class II, materials that change the CMC by modifying solvent-micelle or solvent-surfactant interactions. 

Supercritical fluid extraction (SEE) turns out to be very effective in the isolation of all three surfactant classes from solid matrices. While supercritical CO2 alone did not affect significant recovery of surfactants, the addition either of modifiers or of reactants resulted in nearly quantitative recoveries. Thus, LAS and secondary alkane sulphonates (SAS) are extracted from sewage sludges in the form of tetrabufylammonium ion pairs. Lee et al. extracted NP from sewage... 

CE is a separation technique which uses empty capillaries to effect separation by the electrophoretic movement of charged compounds. Therefore, CE is not a chromatographic method in the strict sense. Recently CE has been applied for the separation and determination of all three surfactant classes (Table 30.7). 

The use of carboxylic and dicarboxylic acids, SDS, bile salts, organic solvents, and alkylammo-nium ions was explored to study the separation of LAS homologues and positional isomers, - as well as alkylether sulfate oligomers. The MEKC separation of mixtures of the surfactant classes coconut diethanolamide, cocamido propyl betaine, and alkylbenzene sulfonate was studied in either low pH phosphate or high pH borate or dipentylamine buffers containing as surfactants deoxy-cholate or SDS, organic solvents (methanol, acetonitrile, n-propanol, and n-butanol), and anionic solvophobic agents (DOSS, fatty acids). " ... 

Since LAS are chromophoric-charged compounds, they are amenable to CZE determination. EKC mode is preferred when homologue discrimination or isomeric distribution is requested or mixture of surfactant classes are screened. " ... 

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