Nonionic surfactants environmental analysis

Depending on the nature of the hydrophilic groups of surfactants, they can be divided into anionic, nonionic, cationic, and amphoteric surfactants. The last-mentioned class only plays a minor role with respect to domestic and industrial applications and practically no methods for the environmental analysis of amphoteric surfactants have been published so far. 

Until now applications of SFC have been limited to product analysis of, e.g., nonionic surfactants but here with great success.No reports on the determination of surfactants in environmental matrices using SFC is known to the authors. 

UV/VIS spectrophotometry is a widely used spectroscopic technique. It has found use everywhere in the world for research, clinical analysis, industrial analysis, environmental analysis, and many other applications. Some typical applications of UV absorption spectroscopy include the determination of (1) the concentrations of phenol, nonionic surfactants, sulfate, sulfide, phosphates, fluoride, nitrate, a variety of metal ions, and other chemicals in drinking water in environmental testing (2) natural products, such as steroids or chlorophyll (3) dyesmff materials and (4) vitamins, proteins, DNA, and enzymes in biochemistry. 

Among different nonionic surfactant classes, alkyl-phenol ethoxylates (APEOs) comprise the class meriting special attention with respect to environmental issues. The analysis of underivatized alkylphenolic compounds by GC-MS is restricted to the most volatile degradation products, such as alkylphenols and APEOs with less then 4-ethoxy groups. To overcome the problem of volatility, different offline and online derivatization protocols have been developed. Two complementary MS techniques, one using El and another using the less commonly used positive (P)CI, have been evaluated for the analysis of APEOs, their acidic (APECs) and neutral metabolites (APs), and halogenated derivatives. 

Lancaster, J. S., P. J. Worsfold, A. Lynes, Nonionic surfactant in aqueous environmental samples by flow injection analysis with chemiluminescence detection. Anal. Chim. Acta, 1990, 239, 189-194. 

Mass spectrometric analysis of cationic surfactants is difficult, so MS has not been applied as much to environmental analysis of cationics as it has to anionics and nonionics. 

Inaba reports that AE-type nonionics may be isolated from environmental waters by toluene extraction (113). The presence of salts, as in sea water, will cause the co-extraction of anionic siufactants and other materials, so that a preliminary ion exchange step may be required prior to extraction. Liquid-liquid extraction with methylene chloride is generally applicable to isolation of ethoxylated surfactants from water (114). Liquid-liquid extraction with chloroform or methylene chloride was found to be equivalent to sublation in concentrating the NPE metabolite nonylphenoxyacetic acids from water. A pH of 2 is suitable for the extraction (35). Sublation was superior for analysis of sewage, since emulsion formation was minimized (115). 

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