The effects of surfactants on the analysis of organic pollutants in natural waters

This paper investigates the interference effects of non-ionic surfactants on the determination of polyaromatic hydrocarbons. A method was developed for the determination of biphenyl, fluorene, anthracene, phenanthracene, chrysene, pyrene, naphthalene. acid acenaphthylene with on line pre-concentration using a 1 cm ODS pre-column. Separation was carried out by HPLC on a 15 cm ODS analytical column using gradient elution with a mobile phase of water and acetonitrile and UV detection at 254 nm. Limits of detection in the range 1 mu gl(-1) were obtained with recoveries of between 90% and 102%. The %RSD for the recoveries were 0.1-10% depending on the samples. Linear alcohol hydrocarbon chain (C13 and C15) nonionic surfactants with a mixture of 3, 7, 11, and 20 polyoxyethylene head groups (Synperonic A3, A7, A11, and A20) were introduced into the PAH standards in levels found in natural waters and the recoveries measured. All the surfactants were found to have an effect on the extraction and recovery, but the degree of effect depended on the hydrophobic chain length and the analyte. Synperonic A3 and A7 had particularly adverse effects for all the PAHs except chrysene. The effects of changes in the sample pH (pH 6-8) and ionic strength on the recovery were also studied. The analysis of natural river water for PAHs was then demonstrated to be: affected by spiking the samples with the surfactants. Methods were investigated to overcome this problem and optimisation of the organic modifier in the mobile phase was found to be most useful. The method was then employed to determine the level of PAH contamination in the River Hull. (C) 1999 Elsevier Science B.V. All rights reserved.