Surfactants NPEC

Fig. 2.6.10. APCI-FIA-MS-MS(+) (CID) daughter ion mass spectrum of selected [M + NH4]+ parent ion (mjz 340) of potential carboxylated non-ionic surfactant metabolite of precursor NPEO prepared by chemical synthesis structure of short-chain NPEC CgHi9-C6H4-0-(CH2-CH2-0)-CH2-C00H fragmentation behaviour under CID presented in the inset [28],... 

While APEO cannot be ionised successfully under negative conditions and consequently for identification MS-MS(—) is not informative, the identification of all anionic APEO derivatives is possible in the negative ionisation mode. For some derivatives, negative as well as positive ionisation can be applied. The loss of the anionic moiety, however, must be taken into account if ionisation is performed in the positive mode. Di-NPEC surfactant homologues submitted to negative CID resulted in the prominent di-alkyl-phenolate ion at m/z 345 (Fig. 2.11.18(a) as shown with the homologue m/z 799 under CID conditions). Therefore, the application of the parent ion scan of m/z 345 in the negative ESI and APCI-FIA-MS-MS mode is very specific for the detection of all anionic derivatives of di-NPEO comparable in... 

For several other non-ionic surfactant metabolites, standards are either commercially available, such as for dicarboxylated polyethylene glycols (DCPEGs) [20], or can be synthesised relatively easily, such as for nonylphenoxy acetic acids (NPECs) [21]. For quantification of metabolites for which standards are absent, the most similar available... 

In view of the inherent resistance of some surfactant metabolite isomers to complete mineralisation, efforts have to be mounted in order to obtain further insight into the reasons behind the persistence of these, such as the SPC and nonylphenol ethoxy carboxylates (NPECs). In order to achieve this, it would thus be indispensable to be able to fully elucidate the chemical structure of individual components, e.g. after isolation from environmental samples. Through the application of, for example, LC-ESI-MS-MS in combination with NMR analyses, this is now possible. 

Important classes of nonionic surfactants are aliphatic poly-ethoxylate alcohols (AEO), and octyl or nonyl phenol polyethoxylates (OPEO and NPEO). The alkylphenol ethoxylates (APEO) attracted special attention due to their supposedly endocrine disrupting properties (Ch. 8.3). LC-MS analysis may also involve nonylphenolethoxycarboxylates (NPEC), biodegradation products of NPEO, and halogenated analogues, generated in chlorine disinfection treatments in drinking water production plants. 

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