Analytical methods for the characterization and determination of nonionic surfactants in cosmetics and environmental matrices

Nonionic synthetic surfactants, constituted of an assortment of classes, are common ingredients of industrial, household and body-care products. Alone or in combination with anionic surfactants, they perform a variety of functions including cleaning action, emulsification, skin conditioning, appearance and consistency modification, solubilization and dispersing agents. By far fatty alcohol ethoxylates (AEs) and alkylphenol ethoxylates (APEs) are more extensively used than any other nonionic surfactant class; however, works appearing in the literature making reference to the analysis of other nonionic surfactant classes have also been collected in this review. The production volume worldwide of AEs and APEs, and consequently their environmental impact, is very high. Although readily biodegraded, stable non-ethoxylated lipophilic residues remain for long periods in the aquatic environment and sediments. In addition to its harmful impact on the food chain, there is also concern on landscape spoiling, particularly in coastal areas. The analytical methods used for quality control of nonionic surfactants in industrial products and in environmental samples are revised and commented upon here. The fundamentals and characteristics of the methods, including their most relevant operative and statistical aspects, are briefly presented. Attention is also paid to the techniques used to extract and preconcentrate the analytes from liquid and solid environmental samples.