Ethoxylate metabolites

Ferguson P.L., C.R. Iden, and B.J. Brownawell (2000). Analysis of alkylophenol ethoxylate metabolites in the aquatic environment using liquid chromatography-electrospray mass spectrometry. Analytical Chemistry 72 4322-4330. 

Ammonia-resistant anionic ethoxylate metabolites, 2 k,2 6 Analytical methods... 

Ferguson, P. L., Iden, C. R., and Brownawell, B. J., Distribution and fate of neutral alkylphenol ethoxylate metabolites in a sewage-impacted urban estuary. Environ. Sci. Technol., 35, 2428-2435, 2001. 

Reversed phase liquid chromatography-mass spectrometry was applied to extracts of Jamaica Bay (New York) water to determine 1-300 xg/l amounts of nonyl phenol ethoxylates and their metabolites [213]. 

Immunochemical methods have been reported for both APEs and their metabolites, especially APs. A discussion of the immunochemical methodologies reported to date, the effect of the immunizing haptens employed, and the features of these techniques were recently reviewed [169]. Unfortunately, the detectability achieved is usually far from what is necessary for direct application to environmental samples. Moreover, the selectivity for APs versus APEs is not always satisfactory. Thus, Goda et al. [ 148] developed a direct ELISA for NP with a LOD of 10 pg L 1 and a working range between 70 and 1,000 pg L, but APEs with one to ten ethoxylate units are also well recognized. 

Octyl- and nonylphenol are well known raw materials used in the surfactant industry since the early 1960s, mainly for the production of their corresponding ethoxylated derivatives (APE). Today, these products have lost considerable importance in this industry as a consequence of substantial environmental threats, resulting from their relatively slow biodegradation, toxicity of their biodegradation metabolites and positive endocrine-disrupting reactions. 

The trend of discovering the analytical field of environmental analysis of surfactants by LC-MS is described in detail in Chapters 2.6-2.13 and also reflected by the method collection in Chapter 3.1 (Table 3.1.1), which gives an overview on analytical determinations of surfactants in aqueous matrices. Most methods have focused on high volume surfactants and their metabolites, such as the alkylphenol ethoxylates (APEO, Chapter 2.6), linear alkylbenzene sulfonates (LAS, Chapter 2.10) and alcohol ethoxylates (AE, Chapter 2.9). Surfactants with lower consumption rates such as the cationics (Chapter 2.12) and esterquats (Chapter 2.13) or the fluorinated surfactants perfluoro alkane sulfonates (PFAS) and perfluoro alkane carboxylates (PFAC) used in fire fighting foams (Chapter 2.11) are also covered in this book, but have received less attention. 

Despite the fact that physico-chemical and chemical degradations were not possible, the isolation of persistent metabolites of the CnF2n+i-(CH2-CH2-0)m-H compound generated by (3 and w oxidations of the terminal PEG unit of the non-ionic blend was reported, but environmental data about this type of compound are still quite rare [49]. TSI(+) ionisation results of the industrial blend Fluowet OTN have been reported in the literature [7,51]. Actual data of non-ionic fluorinated surfactants were applied using ESI- and APCI-FIA-MS(+) and -MS-MS(+), which reported the biodegradation of the non-ionic partly fluorinated alkyl ethoxylate compounds C F2 fi-(CH2-CH2-0)x-H in a lab-scale wastewater treatment process. 

While fast atom bombardment (FAB) [66] and TSI [25] built up the basis for a substance-specific analysis of the low-volatile surfactants within the late 1980s and early 1990s, these techniques nowadays have been replaced successfully by the API methods [22], ESI and APCI, and matrix assisted laser desorption ionisation (MALDI). In the analyses of anionic surfactants, the negative ionisation mode can be applied in FIA-MS and LC-MS providing a more selective determination for these types of compounds than other analytical approaches. Application of positive ionisation to anionics of ethoxylate type compounds led to the abstraction of the anionic moiety in the molecule while the alkyl or alkylaryl ethoxylate moiety is ionised in the form of AE or APEO ions. Identification of most anionic surfactants by MS-MS was observed to be more complicated than the identification of non-ionic surfactants. Product ion spectra often suffer from a reduced number of negative product ions and, in addition, product ions that are observed are less characteristic than positively generated product ions of non-ionics. The most important obstacle in the identification and quantification of surfactants and their metabolites, however, is the lack of commercially available standards. The problems with identification will be aggravated by an absence of universally applicable product ion libraries. 

The quantification of short-chain metabolites from nonylphenol ethoxy-lates (NPEOs) has been carried out in different ways because of the lack of individual standards. Thus, several authors have employed commercial mixtures with low ethoxylation degree and assuming similar molar response factors, such as Marlophen 83 with an average of 3.5 mol of ethylene oxide (EO) [1-5], Imbentin-N/7A, a mixture of NPEOi and NPEO2 (75 25) [6-11] or a mixture of miscellaneous origin [12,13], to quantify NPEOi and NPEO2. 

Ecotoxicological effects have been demonstrated for a number of surfactants or their metabolites, including some still currently in use, such as the nonylphenol ethoxylates [1], and as such there is a necessity to find more environmentally acceptable alternatives. Whilst the silicones are not the major surfactant type in use to date, the efficient properties and indications of low environmental persistence and toxicity demonstrate their potential for widespread use [2-4]. Relatively little is known about these new, rapidly emerging surfactants and the purpose of this chapter is thus to collate the available data, present new data, and identify the future research required in this area in order to evaluate the environmental relevance of this class of surfactants. 

In this chapter, in addition to presenting a comprehensive summary of reviews already published about the presence of APEOs and their metabolites [9,10], which cover mainly nonylphenol (NP), NP mono-ethoxylate (NPEOi) and NP diethoxylate (NPEO2), we focus on describing a complete picture of APEO and so far known metabolites, including those less widely investigated, such as the NP ethoxycarboxylates (NPECs). 

The only study available on metabolites of AE was performed by Crescenzi et al. [17]. The initial biodegradation of AE occurs by cleavage at the ether bridge between the alkyl and ethoxylate chain, resulting in polyethylene glycols (PEG) and alcohols. In consecutive oxidation steps, the PEG chains are shortened and mono- and dicarboxylated metabolites (MCPEG and DCPEG, respectively) are formed. 

Kvestak and Ahel investigated the biotransformation kinetics of A9PEO in the Krka estuary in Croatia [35]. Static die-away tests were performed with autochthonous bacterial cultures originating from the two compartments of the stratified estuary the upper fresh/brackish water layer and the lower saline water layer. Experiments were performed at three different temperatures, and at two concentrations. Samples were taken daily and all separate ethoxylates (1-16) were quantified by normal phase HPLC-FL analysis. No other metabolites were analysed. 

Alkylphenol ethoxylates (APEO) are no longer used in household detergents in the Western world and represent only a minor portion of the whole non-ionic surfactants group. Even if APEO is a group of surfactants of no commercial importance anymore, there is a need for risk assessment since these compounds are still present in the aquatic environment due to the recalcitrant nature of some of their metabolites (see Chapters 6.1, 6.2.1, 6.3.1 and 6.4). More attention should be given in the future to other non-ionic surfactants like alcohol ethoxylates. 

In general, the main pollution problems associated with surfactants can be summarized as (1) foaming in river and wastewater treatment plants [314,326, 344,348,349,356,357], (2) transformation to bioactive metabolites (i.e., poly-ethoxylated alkylphenols, estrogenic compounds) under aerobic and anaerobic conditions [315,356], and (3) formation of certain cationics which are toxic to microorganisms at high concentrations [356,357]. 

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