Nonylphenol ethoxylates quantification

For analysis of surfactants, i.e. detection, identification and quantification, LC-TSP-MS and MS/MS are also qualified methods for substance-specific information [600-602]. A mixture of non-ionic surfactants, comprising nonylphenol ethoxylates [C9Hi9-(CeH4)-0-(CH2-CH2-0)m-H], anionic surfactants and PEG, was... 

Linear alkylbenzenesulfonates (LAS), alcohol ethoxylates (AEO), and nonylphenol ethoxylates (NPEO) are synthetic surfactants used in the formulation of detergents and other cleaning products and are widely applied in the dye and leather industry and other industrial processes. These compounds, considered as estrogenic, have aroused considerable interest due to the large quantities produced globally. Their low volatility and anionic form make LC-based methods the preferred approach [7]. Due to the presence of different positional isomers, to the biodegradation intermediates, and to the lack of reference standards, LC-MS, and in particular with ESI, is the only technique which enables their identification and quantification in environmental waters. 

Excellent selectivity for APE is provided by fluorescence detection. Quantification in reversed-phase mode requires only the measurement of the single peak for nonylphenol ethoxylates (octylphenol derivatives are rarely found), while normal phase chromatography permits determination of the homolog distribution (104,106). For even more selective fluorescence detection of APE, the analysis may be made with and without acetylation. Many impurities lose their fluorescence after acetylation. The change in retention time of the acetylated compounds confirms the identity of the APE peaks (93). Fluorescence detection is much more sensitive than UV detection for nonylphenol (105). 

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. 

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