A three-year project funded by the Department of Energy's Environmental Management Science Program (EMSP) has yielded major advancements in sensor technology for hazardous-waste monitoring applications. The new spectroelectrochemical sensor, developed by scientists at the University of Cincinnati and the Pacific Northwest National Laboratory in Richland, Wash., relies upon three modes of selectivity rather than the usual one or two modes conventional sensors use.
Spectroscopy, electrochemistry, and selective coating are the three modes of selectivity this sensor uses. It's based on waveguide technology, which propagates a light beam along the sensor core (see the figure). The sensor takes accurate measurements quickly when placed in a waste tank. Also, it may be left in a waste tank to monitor target levels for an extended period of time.
The sensor coating developed by the research team is selective for ferrocyanide, a target compound found within the mixture of substances often contained in underground waste tanks. This selective coating allows only certain compounds to enter the sensor while excluding others. For instance, the coating may permit all negatively charged ions to enter the sensor while restricting all positively charged ions.
Employing electrochemistry as a mode of selectivity, an electrical potential is applied to electrolyze a smaller group of compounds. A specific wavelength of light is then utilized to detect the compound of interest. In the version of the sensor developed by this team, light is used to detect the presence of ferrocyanide.
Using these three modes of selectivity, the spectroelectrochemical sensor measures target compounds while excluding other contaminants. The sensor proved its effectiveness while testing waste containing actual ferrocyanide at Pacific Northwest.
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