In-situ electrochemical method for detecting freely dissolved polycyclic aromatic hydrocarbons in water

Abstract

Environmental context Polycyclic aromatic hydrocarbons (PAHs) are potentially carcinogenic and mutagenic compounds found in the atmosphere, soil, sediments and water. They can bioaccumulate in marine organisms where they pose a threat to the health of the organisms. We are developing a low-cost and simple electrochemical method to monitor the concentrations of these compounds in the aquatic environment. Abstract A new sensing system for polycyclic aromatic hydrocarbons (PAHs) in waters is being developed. The system consists of a wafer-based device with a chip-based mercury on platinum microelectrode as a working electrode and a platinum auxiliary electrode, incorporated into a flow cell system with an external reference electrode. The Hg microelectrode was coated with a phospholipid–triglyceride mixed layer and interactions between anthracene, phenanthrene, pyrene and fluoranthene and the layer were monitored using rapid cyclic voltammetry. The layer proved sensitive to interactions with PAHs in ‘organic matter free’ seawater, with respective detection limits of 0.33, 0.35, 0.15 and 0.32μgL–1 for phenanthrene, pyrene, anthracene and fluoranthene. Tested interferences, such as sodium humate, dextran T-500 and bovine serum albumin, representing humic substances, polysaccharides and proteins, did not have an influence on the layer response. The system was also tested with a river water sample where concentrations of PAHs were determined using the standard addition method and compared with the results obtained by using gas chromatography–mass spectrometry (GC-MS). The concentration of total PAHs obtained by the standard addition method is ~80% lower compared with the results obtained by GC-MS analysis. The difference is explained by the fact that the electrochemical method measures water-soluble and free PAHs whereas the chromatographic method measures both dissolved and particulate–organic PAHs.