Determination of priority carcinogenic polycyclic aromatic hydrocarbons in wastewater and surface water by coacervative extraction and liquid chromatography-fluorimetry

The US Environmental Protection Agency (EPA) and the European Union (EU) have set restrictive limits for priority carcinogenic polycyclic aromatic hydrocarbons (CPAHs) in surface waters (EPA 3.8ngL⁻¹and EU 2-100ngL⁻¹) in order to protect aquatic life and human health. Currently, methods meeting these sensitivity criteria are not suitable for routine analysis of CPAHs. Here, we present a simple, rapid and low-cost method for the routine monitorization of these pollutants in aquatic environments based on their extraction with coacervates of decanoic acid reverse micelles in the nano- and microscale, and determination by liquid chromatography-fluorimetry (LC-FL). The method involves the stirring of filtered aqueous samples (36mL) with 4mL of THF containing 70mg of decanoic acid for 5min, its centrifugation for 10min and the analysis of 20μL of the resulting coacervate containing the CPAHs by LC/FL. The method is robust, the extractions being independent on salt concentration (up to 1M), temperature (up to 60°C) and pH (below 4). Besides, the coacervate prevents the CPAHs from adsorption onto the surface of containers during sample storage. No clean-up steps are necessary and the method is matrix-independent. The quantification and detection limits of the method ranged between 0.4 and 3.5ngL⁻¹ and 0.1 and 1ngL⁻¹, respectively, for the seven priority CPAHs. The method has been successfully applied to the determination of these pollutants in raw and treated sewage from three mechanical-biological treatment plants, two rivers and a reservoir with frequent motorized recreational craft activities, all of them located in the South of Spain. Recoveries for spiked samples in the range 2-30ngL⁻¹ were between 88 and 95% with relative standard deviations from 1 to 7%. CPAHs were present in wastewater influents at concentrations in the range 3.9-37ngL⁻¹, while the treatment at the WWTPs studied reduced their concentration in their respective effluents in a percentage near 100%. Three CPAHs were present at quantifiable levels in Guadajoz river (1.8-6.6ngL⁻¹) and six in La Breña reservoir (1.39-4.8ngL⁻¹).