ABSTRACT
CONTENTS 24.1 Introduction ..................................................................................................................... 668
24.1.1 General Remarks .............................................................................................. 668 24.1.1.1 Anionic Surfactants......................................................................... 669 24.1.1.2 Nonionic Surfactants ...................................................................... 669 24.1.1.3 Cationic Surfactants ........................................................................ 669
24.2 Sampling........................................................................................................................... 671 24.3 Isolation and Enrichment .............................................................................................. 671
24.3.1 Solid-Phase Extraction ..................................................................................... 672 24.3.1.1 Anionic Surfactants......................................................................... 672 24.3.1.2 Nonionic Surfactants ...................................................................... 672
24.3.2 Liquid-Liquid Extraction................................................................................ 673 24.3.3 Solid-Liquid Extraction................................................................................... 673 24.3.4 Other Methods .................................................................................................. 674
24.4 Determination Procedures............................................................................................. 674 24.4.1 Colorimetry/Titrimetry.................................................................................... 674
24.4.1.1 Anionic Surfactants......................................................................... 674 24.4.1.2 Nonionic Surfactants ...................................................................... 675 24.4.1.3 Cationic Surfactants ........................................................................ 675
24.4.2 High-Performance Liquid Chromatography ............................................... 675 24.4.2.1 Anionic Surfactants......................................................................... 675 24.4.2.2 Nonionic Surfactants ...................................................................... 679 24.4.2.3 Cationic Surfactants ........................................................................ 680
24.4.3 Gas Chromatography ...................................................................................... 681 24.4.3.1 Anionic Surfactants......................................................................... 681 24.4.3.2 Nonionic Surfactants ...................................................................... 684 24.4.3.3 Cationic Surfactants ........................................................................ 684
24.4.4 Supercritical Fluid Chromatography ............................................................ 684 24.4.5 Capillary Electrophoresis ................................................................................ 685
24.4.5.1 Anionic Surfactants......................................................................... 685 24.4.5.2 Nonionic Surfactants ...................................................................... 685 24.4.5.3 Cationic Surfactants ........................................................................ 685
24.4.6 Mass Spectrometry........................................................................................... 685 24.4.6.1 Anionic Surfactants......................................................................... 688 24.4.6.2 Nonionic Surfactants ...................................................................... 688 24.4.6.3 Cationic Surfactants ........................................................................ 688
24.4.7 Infrared Spectroscopy...................................................................................... 688 Abbreviations ............................................................................................................................. 689 References ................................................................................................................................... 690
Surfactants have amphiphilic structures consisting of a hydrophilic and a hydrophobic part. These special structures cause their surface-active properties like concentration at surfaces, reduction of the surface tension, and formation of micelles in bulk solution. Therefore, they are widely used in formulations for washing, wetting, emulsifying, and dispersing. Laundry detergents, cleaning agents, and personal care products are by far the largest class of surfactant-containing products for domestic use. After use they are mainly discharged into municipal wastewaters, which enter sewage treatment plants. The different ingredients of a detergent formulation are eliminated by biodegradation or adsorption. In the case of insufficient biological degradability, however, they are a potential source of environmental pollution. Tetrapropylene benzene sulfonate (TPS) is a typical example of a persistent anionic surfactant, which was used in detergents between 1946 and 1965. As a consequence of rising TPS concentrations in German rivers during the dry years of 1959/1960 visible foam formed on the water surface. As a reaction, strict standards were applied to surfactants with regard to their biodegradability. In a directive of the European Community (73/404/EEC) [1], an average biodegradation rate of at least 90% for all surfactants (referring to a certain residence time in a municipal sewage treatment plant) is required. Consequently, TPS was replaced by readily biodegradable linear alkyl benzene sulfonates (LAS) in the 1960s.
