Electrochemical (Bio)sensors for Mercury Speciation in Air and Wet Deposition

Recently, global traceability and measurements of mercury have been addressed with a network approach using automated and/or semiautomated systems for sampling and detection in air and wet deposition. Based on the commonly used analytical procedures for the determination of mercury in precipitation within the GMOS global network, it has been highlighted the disadvantage of more than 40monitoring sites of requiring significant running costs for sampling and shipping samples back to the reference laboratories, especially in remote regions such as Antarctica or in pristine areas that do not have basic infrastructures (i.e., no clean labs, poor power supply). On long term, the management sustainability of global or continental scale monitoring networks for measuring mercury in precipitation samples depends very much on our ability to develop advanced online sensor capable to measure total mercury concentrations or even better if speciated mercury concentrations during precipitation events, including snow samples. These advanced sensors should be robust, traceable and should not require gas carrier, significant energy supply and highly qualified technical expertise. Having the above in mind, our goal is to present preliminary results of newly developed sensor/biosensor which has the advantage of not requiring any pretreatment of samples, it is very sensitive, can reach ultra trace level, does not require significant power supply and is not expensive. Recently, the use of smart biological molecules and/or nanostructured materials have greatly increased the performance of biosensors by making them stable, reproducible, suitable for field measurements or for monitoring of processes and emissions from power plants and other industrial sources: this is the case of printed electrochemical biosensors. The electrodes are printed on a flexible plastic substrate, are cheap and for this reason they can be used as consumables for one shot field measurement or for long term measurements, too. Nanostructures (gold nanoelectrode ensembles, quantum dots), biological components and conductive polymeric wires (doped polyaniline) are electrochemically deposed on the electrode surface for obtaining the best performances in mercury determination. Results are compared with traditional instrumentation using reference analytical methods (CVAFS / USEPA Method 1631 rev. E) for determination of Hg in wet deposition. Preliminary results obtained withimpedimetric (EIS, Electrochemical Impedance Spectroscopy) sensors and traditional instrumentation are discussed with the aim of their integration in an automatic collector for Hg in air and/or wetonly deposition.