Results of collaborative interlaboratory study to estimate the performance characteristics of the gas chromatographic method for some alkyl phenols from water

4-tert-octylphenol and 4-nonylphenol are two major metabolites of alkylphenol polyethoxylates which are widely used in different industrial and commercial applications as non-ionic surfactants. In order to ensure the ecological security by controlling the concentrations of these pollutants in water it was developed a gas chromatographic method after extraction with dichloromethane at pH = 3.5. The estimation of the performance characteristics of the method was performed by a collaborative interlaboratory study. Each participant laboratory has analysed a set of five water samples with 4-tert-octylphenol and 4-nonylphenol in different levels of concentration. The results obtained after the statistic processing of the experimental data showed that the standard deviations of repeatability and reproducibility are lying in the normal domains for a chromatographic method. Consequently, the proposed method can be used by any environmental laboratory which performs the control of the level of pollution with these two compounds.