Portable Analyzer Based on Microfluidics/Nanoengineered Electrochemical Sensors for in Situ Characterization of Mixed Wastes

Portable Analyzer Based on Microfluidic/Nanoengineered Electrochemical Sensors for in Situ Characterization of Mixed Wastes PI: Dr. Joseph Wang (In Collaboration with the PNNL PI Dr. Y. Lin). Objective of Research: This research effort aims at developing a portable analytical system for fast, sensitive, and inexpensive, on-site monitoring of toxic transition metals and radionuclides in contaminated DOE Sites. The portable devices will be based on Microscale Total Analytical systems ( -TAS) or 'Lab-on-a-chip' in combination with electrochemical (stripping-voltammetric) sensors. The resulting microfluidics/electrochemical sensor system would allow testing for toxic metals to be performed more rapidly, inexpensively, and reliably in a field setting. Progress Summary/Accomplishments: This report summarizes the ASU activity over the second year of the project. In accordance to our original objectives our studies have focused on various fundamental and practical aspects of sensing and microchip devices for monitoring metal contaminants. As described in this section, we have made a substantial progress, and introduced effective routes for improving the on-site detection of toxic metals and for interfacing microchips with the real world. This activity has already resulted in 7 research papers (published or in press in major international journals). The electrochemical sensors being developed rely on the highly sensitive adsorptive stripping voltammetry (AdSV) technique to detect metal ions of interest to the DOE, particularly uranium and chromium. Traditionally, AdSV measurements of U and Cr require the use of mercury electrodes which are not suitable attractive for field deployment. Our initial goal was thus to replace these toxic mercury electrodes with 'environmentally-friendly' sensor materials. In particular, we demonstrated recently that bismuth-film electrodes offer high-quality measurements of heavy metals that compare favorably with that of mercury electrodes. Bismuth is a 'green' element, with very low toxicity, and widespread pharmaceutical use. A major effort of our activity this year has been devoted to the development of a 'mercury-free' uranium sensor based on the bismuth film electrode. Bismuth-coated carbon-fiber electrodes have thus been successfully applied for adsorptive-stripping voltammetric measurements of trace uranium in the presence of the cupferron complexing agent