Alkylphenols quantification

For the quantification of alkylphenol ethoxylates (APEOs), several related compounds have been used as internal standard, e.g. for recovery determination, decylphenol monoethoxylate [20]. Octylphenol nonaethoxylate (t-0PE09) was synthesised by reacting octylphenol (OP) with 1,2-6j.s(2-chloroethoxy)ethane to give the chloro derivative, followed by reaction with the sodium salt of hexaethylene glycol [21,22], Another approach used the synthetic standard l-(4,-methoxyphenyl)-hexan-l-ol as a surrogate to monitor the efficiency of the extraction for... 

A source of error in the HPLC method is the very short retention time of PEG in reversed-phase systems. This makes quantification by differential refractive index subject to interference by peaks from water, solvent impurities, and other unretained substances. This source of error may be eliminated by coupling the HPLC column to a GPC column, so that PEG is resolved from both the surfactant and from other impurities (36). Even with this modification, if phenol impurity were present in the initial alkylphenol, the resulting ethoxylated phenol could interfere with PEG determination by this method. Its presence is detected by using a UV detector in series with the RI detector. Another source of interference is the anion, such as acetate or lactate, added during the neutralization of the catalyst. For careful work, this should be removed by ion exchange prior to HPLC analysis (36). 

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