Determination of poly(ethylene glycol)s in environmental samples by the indirect tensammetric method

Abstract

Poly(ethylene glycol)s (PEGs) are one of major metabolic products of the biodegradation of non-ionic surfactants (NS). Therefore, a method for the determination of PEGs in mixtures of metabolic products of the biodegradation of NS would be useful in the control of the aquatic environment. In order to solve this problem, the indirect tensammetric method (ITM) combined with an adequate separation scheme was applied. The analytical signal in the ITM reacts additively on both PEGs and NS. Therefore, NS interfere with the determination of PEGs. In order to separate NS, extraction with ethyl acetate was used. Sequential extraction of the sample with chloroform resulted in the separation of PEGs. The residue after evaporation of an aliquot or the whole chloroform phase was analysed using the ITM. The recovery and precision were checked on the example of a PEG of M_r 600. The recovery was 92 and 96% for 100 and 1000 µg spikes of PEG, respectively and the relative standard deviation was 5.6 and 3.4%, respectively. The problem of the choice of standard and the error related to this choice are discussed. The developed method was used for the determination of PEGs in mixtures formed during the testing of the biodegradation of oxyethylated alcohols under the OECD Confirmatory Test and in die-away experiments on ‘native’ NS of river water. In both cases PEGs were found to be major metabolic products. The method was also applied to the determination of PEGs in river water.