Anionic surfactants in acid media: a new cloud point extraction approach for the determination of polycyclic aromatic hydrocarbons in environmental samples

Abstract

Anionic surfactants separate into two isotropic phases in an acid medium at room temperature and can be successfully used in the cloud point extraction methodology. In this work, the anionic surfactant sodium dodecane sulphonic acid (SDSA) has been used for the extraction and preconcentration of the 16 polycyclic aromatic hydrocarbons (PAHs) classified as priority pollutants by the EPA from water samples (network supply, underground and river). Subsequent separation by HPLC and quantification using fluorimetric detection and wavelength programming has allowed these pollutants to be determined with detection limits from nanograms to subnanograms per litre. The use of SDSA offered two significant advantages about the nonionic surfactants generally utilized in the cloud point methodology for extraction of PAHs, namely, low fluorescence and absorbance signals at the PAHs detection wavelengths (because of the absence of an aromatic moiety in the surfactant molecule), and a low chromatographic retention time (owing to the polar character of SDSA). These features allowed the sensitive determination of the more polar PAHs without the need of a clean-up step to remove the surfactant. Negligible sorption of PAHs onto the containers when SDSA is added as a stabilizing agent, desorption of these pollutants if the sample has been collected without preservation and high recoveries, even in the presence of considerable levels of humic acids, were other features found for the proposed SDSA micelle mediated extraction of PAHs.