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Rapid on-site measurements of arsenic (As) are essential for the timely remediation of As-contaminated groundwater for both municipal and emergency response applications. Current field tests suffer from either complicated end-user instructions or a lack of accuracy and specificity. The system presented here combines a whole-cell bacterial biosensor with an electrochemical measurement that provides enhanced accuracy and signal intensity compared to traditional bacterial-detection approaches. When integrated within a customized hardware system, this whole-cell sensor demonstrated excellent specificity and sensitivity. This fast, sensitive, and easy-to-use approach is a viable alternative for on-site arsenic testing. [ABSTRACT FROM AUTHOR]

A commercial digital simulation tool was used to simulate cyclic voltammetry (CV) data for redox mediation electrode reactions involving immobilized redox mediators. The system studied consists of a ferrocene-based redox mediator in an alkanethiolatebased self-assembled monolayer (SAM) on gold, with ferrocyanide in solution acting as electron donor to react with electrogenerated ferrocenium in the monolayer. Simulation parameters include rate constants for ferrocene oxidation/reduction in the monolayer, the mediation cross reaction between ferrocenium in the monolayer and ferrocyanide in solution, and the direct (unmediated) ferrocyanide oxidation/reduction reaction by long-range electron transfer across the monolayer. An excellent agreement between simulation and experiment was obtained using simulation parameters derived from independent experiments. The simulation method enables analysis of an entire voltammogram which can offer advantages over analytical approaches that consider only a portion of the data (e.g., a “foot-of-the-wave” analysis). The availability of a validated simulation tool allows questions about the anticipated reactivity of immobilized redox mediators to be addressed definitively via simulation, rather than by speculation on the effects one might expect to observe on a CV waveshape for a particular parameter change. [ABSTRACT FROM AUTHOR]