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

A new sensing system for polycyclic aromatic hydrocarbons (PAH) in waters is being developed. The system consists of a wafer based device with chip-based mercury (Hg) on platinum microelectrode as working electrode and platinum auxiliary electrode, incorporated in to a flow cell system with an external reference electrode. 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 (RCV). The layer proved sensitive to interactions with PAHs in “organic matter free” seawater, with the detection limits of 0.33 μg/L for phenanthrene, 0.35 μg/L for pyrene, 0.15 μg/L for anthracene and 0.32 μg/L for fluoranthene. Tested interferences, such as sodium humate, dextran T–500 and bovine serum albumin, representative 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 to the results obtained by using gas chromatography–mass spectrometry (GC–MS). The concentration of total PAH obtained by the standard addition method is about 80% lower compared to the results obtained by GC MS analysis. The difference is explained by the fact that the electrochemical method measures water-soluble and free PAHs while chromatographic methods measures both dissolved and particulate/organic PAH