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Mixed lipid monolayer electrochemical biosensor for detection of lipophilic pollutants in aquatic environment

The aquatic environment is exposed to an increasing amount of pollution from various sources. In order to protect the Earths diverse ecosystems close monitoring and early detection of potentially dangerous substances is crucial. Most common pollutants found in the aquatic environments are biomembrane active lipophilic substances such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, tributyltins and others. Lipophilic pollutants interact with phospholipid monolayers and this can be monitored using a phospholipid monolayer on a mercury (Hg) electrode surface, where the compounds cause disruption of the monolayer's structure and fluidity. This interaction, which is observed through changes in the monolayer reorientation peak potential and height, is monitored electrochemically by using out-of-phase alternating current voltammetry (ac) and rapid cyclic voltammetry (rcv) in an automated flow cell system which incorporates a chip-based Hg microelectrode [1, 2]. A mixed monolayer of palmitoyl-2-oleoyl-sn-glicero-3-phosphocholine (POPC) and triolein, a trigliceride of oleic acid (TG), in 3:1 molar ratio, proved to be very sensitive to the presence of the polycyclic aromatic hydrocarbon phenantrene. Figure 1 shows a shift in the potentials of the reorientation peaks of the sensing monolayer of POPC and TG with increasing concentrations of phenanthrene. The lowest detection limit is 2 μg L-1. Further work involves optimising the monolayers in order to make them succeptible to different pollutants and subsequently incorporating the flow cell into a robust system for use in-situ. References: [1] Coldrick, Z., Steenson, P., Millner, P., Davies, M., Nelson, A., Electrochimica Acta 2009, 54, (22), 4954-4962. [2] Coldrick, Z., Penezic, A., Gasparovic, B., Steenson, P., Merrifield, J., Nelson, A., J. Appl. Electrochem., manuscript submitted March 2011.

electrochemical; aquatic; pollution; lipids

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