Strategies for selecting optimal sampling and work-up procedures for analysing alkylphenol polyethoxylates in effluents from non-activated sludge biofilm reactors.

Trace-level analysis of alkylphenol polyethoxylates (APEOs) in wastewater containing sludge requires the prior removal of contaminants and preconcentration. In this study, the effects on optimal work-up procedures of the types of alkylphenols present, their degree of ethoxylation, the biofilm wastewater treatment and the sample matrix were investigated for these purposes. The sampling spot for APEO-containing specimens from an industrial wastewater treatment plant was optimized, including a box that surrounded the tubing outlet carrying the wastewater, to prevent sedimented sludge contaminating the collected samples. Following these changes, the sampling precision (in terms of dry matter content) at a point just under the tubing leading from the biofilm reactors was 0.7% RSD. The findings were applied to develop a work-up procedure for use prior to a high-performance liquid chromatography-fluorescence detection analysis method capable of quantifying nonylphenol polyethoxylates (NPEOs) and poorly investigated dinonylphenol polyethoxylates (DNPEOs) at low microg L(-1) concentrations in effluents from non-activated sludge biofilm reactors. The selected multi-step work-up procedure includes lyophilization and pressurized fluid extraction (PFE) followed by strong ion exchange solid phase extraction (SPE). The yields of the combined procedure, according to tests with NP10EO-spiked effluent from a wastewater treatment plant, were in the 62-78% range.

Development of a high-performance liquid chromatography-fluorescence detection method for analyzing nonylphenol/dinonylphenol-polyethoxylate-based phosphate esters.

A novel reversed phase HPLC method for the simultaneous analysis of surfactants containing nonylphenol/dinonylphenol-polyethoxylates and their o-phosphate esters is reported, in which eluting substances are detected fluorescently. Their chemical structures were elucidated by direct infusion electrospray-mass spectrometry in positive mode. The limits of quantification and range of the method were determined to be 0.1mg and 0.1-100 mg surfactant L(-1), respectively, with a reproducibility (RSD) at a concentration of 38 mg surfactant L(-1) of 5.6%. The accuracy was determined by spiking selected process water samples with known amounts of surfactant, and recoveries were typically in the 82-102% range.