Pregled bibliografske jedinice broj: 349509
Determination of surfactants and related compounds in sewage effluents
Determination of surfactants and related compounds in sewage effluents // Book of abstracts / Petrović, Mira ; Barcelo, Damia (ur.).
Barcelona, Španjolska: CSIC, Barcelona, Španjolska, 2007. str. 32-34 (plenarno, nije recenziran, sažetak, znanstveni)
Determination of surfactants and related compounds in sewage effluents
Ahel, Marijan ; Terzić, Senka
Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni
Book of abstracts / Petrović, Mira ; Barcelo, Damia - Barcelona, Španjolska : CSIC, Barcelona, Španjolska, 2007, 32-34
Emerging contaminants in wastewaters: monitoring tools and treatment technologies
Mjesto i datum
Beograd, Srbija, 26.-27.04.2007
Analysis; surfactants; sewage effluents
Synthetic surfactants are one of the most important classes of the modern man-made chemicals, which are used in large quantities for various purposes in industry and households. Manufacture of surfactants represents currently one of the most profitable branches of the chemical industry. The estimated global annual consumption rate exceeds 10 Mt of which 23 % in Western Europe (CESIO, 2002). Unique amphiphilic design of surfactant molecules represents the basis for their widespread use in various water-related applications, mainly as detergents and cleaning agents. As a consequence, surfactants belong to the most abundant contaminants in municipal and industrial wastewaters and should be considered highly relevant regarding possible adverse effects in the aquatic environment. In early 1960s, the phenomenon of foaming rivers, caused by the increasing use of the anionic surfactants of the first generation, tetrapropylenebenzene sulphonates, triggered a growing concern about the environmental impact of surfactants, and about their biodegradability in particular (Knepper et al., 2003). Strict regulations related to surfactant degradation and new technological challenges have led to the design of a large number of structurally different surfactants, which can be divided, according to the chemical character of their hydrophilic moiety, into the 4 main categories: anionic, non-ionic, cationic and amphoteric. Such a development represents a huge challenge for their analytical determination. Moreover, it should be stressed that most of the commercial surfactants are very complex mixtures of closely related compounds, including isomers, homologues and oligomers, which makes their detailed analysis an extremely difficult task. The availability of adequate analytical methods is the key prerequisite for a successful study of the surfactant behaviour and fate in wastewater treatment and in the aquatic environment. Many environmental problems, associated with the use of synthetic surfactants, were recognised with a significant time-delay after their indiscriminate introduction in various applications, mainly due to the lack of reliable and comprehensive analytical methodologies, especially the methods for the determination of their degradation products. Early studies of surfactants in environmental and biodegradation studies were carried out mainly using collective spectrophotometric methods for the determination of the major surfactant groups, including MBAS method for the determination of anionics, BiAS method for the determination of non-ionics and CTAS for the determination of cationics. These methods are still in use in many countries as standard methods for monitoring purposes, however, they can be regarded adequate only for a crude estimate of the total load of the parent surfactants. However, there have been several examples in the past 30 years which clearly indicated that a comprehensive environmental risk assessment must include all possible degradation products, which in some cases represent the most critical ecotoxicological issue (Ahel et al. 1994). This problem can be addressed only by using modern high-resolution separation techniques. Regarding applicability of different chromatographic techniques for the surfactant analyses, it should be stressed that surface-active molecules are designed to possess amphipathic properties and therefore include both hydrophobic and hydrophylic moiety in their structure. The hydrophilic moiety ensures sufficient solubility of a surfactant in water, but in the same time it dramatically lowers the volatility of the hydrophobe to which it was added. Therefore, gas chromatography cannot be considered as a first-choice technique in the surfactant analysis, although there were several very successful GC applications, which involved formation of thermally stable derivatives prior to the analysis. The most popular and most common modern separation technique for the determination of surfactants in high-performance liquid chromatography (HPLC), in particular the reversed phase HPLC, which easily copes with highly polar and/or large surfactant molecules exceeding molecular weight of 1000 Da. However, early applications of this technique suffered from the lack of sensitive detection systems required for the environmental analyses since many classes of surfactants are aliphatic compounds, which do not possess strong chromophores suitable for the UV or spectrofluorimetric detection. Nevertheless, HPLC separation with spectrofluorimetric detection proved to be an exellent metod for the determination of aromatic surfactants and led to some important insights for their risk assessment. Recent developments of new hyphenated techniques, especially liquid chromatography – mass spectrometry (LC/MS), has given rise to unprecedented advances in the analyses of surfactants and their metabolites (Gonzalez et al. 2007). This powerful technique ensures high separation power, unambiguous identification and highly sensitive detection of different surfactant classes, opening a new route for their ultimate environmental risk assessment. As an illustration of the importance of the comprehensive analytical approach in the environmental risk assessment of surfactants, this paper will focus on the two prominent aromatic surfactants, including anionic linear alkylbenzene sulphonates (LAS) and non-ionic alkylphenol polyethoxylates (APnEO). LAS are the most prominent surfactant class with annual world consumption of 2.9 Mt, contributing with 40-50 % to the total consumption anionic surfactants, while APnEO are the second most important group of non-ionic surfactants with estimated annual consumption of 0.6 Mt. Moreover, both classes show a complex metabolic pattern in sewage treatment, which requires very complex analytical approach to study their behaviour and fate as well as possible adverse effects. Determination of LAS and their main metabolites can be achieved in a single run using a gradient reversed phase HPLC separation and detection based on MRM LC/MS. The chromatographic procedure allows efficient separation of LAS-related compounds, spanning from sulphophenyl carboxylates (SPE) as the main metabolic products, to different homologues of parent LAS as well as impurities such as dialkyltetraline sulphonates (DATS). The approach to the analysis of APnEO is more complex, due to the more complex composition of the parent compounds, which includes a mixture of various oligomers (typical range from 1-20 ethoxy units, homologues (C8, C9 alkyl chains) and isomers (branching of the alkyl chain ; o- and p-substitution of the benzene ring). Moreover, APnEO show a unique metabolic pattern characterised by the formation of both hydrophilic and hydrophobic transformation products (Ahel et al., 2004). Due to such an enhanced complexity even the most sophisticated methods like LC/MS cannot provide reliable analyses of this surfactant class in a single run. The parent compounds can be detected by LC/MS technique using positive electrospray ionization, however, the response of individual oligomers can be highly variable, which represents a problem for reliable quantitation, especially for the smallest and most lipophilic oligomers. Alternatively, individual oligomers can be determined by a simple normal phase HPLC with spectrofluorimetric detection using aminosilica columns. The anionic metabolites, including alkylphenoxycarboxylic acids (APEC) and the most toxic metabolites alkylphenols (AP) can be determined very selectively at a high sensitivity using reversed-phase LC/MS with electrospray ionization in negative mode using MRM technique. Examples of surfactant behaviour and mass balance studies in sewage treatment, including both dissolved and particulate phases, using complex analytical approach will be shown. Literature 1. European Committee of Surfactants and their Organic Intermediates (CESIO), Statistics, 2002 (http://www.cefic.be/files/Publications/cesio02_010903.xls). 2. Knepper T.P., Barcelo D and De Voogt P. Analysis and Fate of Surfactants in the Aquatic Environment (Wilson& Wilson’ s comprehensive analytical chemistry ; Vol. 40), Elsevier, Amsterdam, 2003, pp 966. 3. Ahel M., Giger W. and Koch, M., Water Research, 28, 1994, 1131-1142. 4. Gonzalez S, Petrović, M and Barcelo D., Trends in Analytical Chemistry, 26, 2007, 116-124.