Determination of alkylphenol ethoxylate non-ionic surfactants in trade effluents by sublation and high-performance liquid chromatography

Abstract

Alkylphenol ethoxylate (APE) non-ionic surfactants can be extracted from trade effluents into ethyl acetate by salting out and sublation (gas stripping). The dried extracts are rapidly evaporated in a Kuderna–Danish evaporator and the residue is dissolved in acetonitrile. Finally, co-extractives are precipitated out by chilling to –5 °C and the surfactant is determined in the supernatant by HPLC with fluorescence detection. An internal standard consisting of a single APE oligomer (tert-octylphenol with a nine ethoxylate unit side-chain) compensates for incomplete recovery of the surfactants. The method is applicable to APEs at concentrations of 0.1–50 mg l^–1.