| With a number of Superfund sites in Federal Regions 1 and 2 having some form of heavy metal contamination, the ability to obtain real-time screening data for heavy metals for remediation of ground water at purported hazardous waste sites is critical, but is lacking. The objective of this research was to develop and demonstrate the utility of a low-cost, field portable analytical device for the rapid screening of heavy metals in ground water. Microfabricated iridium and gold arrays, the heart of the device, were implemented to this end because they are small, rugged, relatively inexpensive, and provide measurable currents at the low parts-per-billion to parts-per-trillion level.; With support from the Northeast Hazardous Substance Research Center at New Jersey Institute of Technology, the electrochemically-based metal analyzer (EMA) was developed. Mercury was deposited onto the iridium arrays (Ir(Hg)UMEAs) for all experiments. Studies demonstrated reproducibility, stability, and reasonable lifetimes. The analytical capabilities of the UMEAs were investigated and verified with comparisons to standard EPA spectrometric methodologies. Excellent linearity was obtained with both arrays when concentrations and the SW frequencies were varied. Experimental detection limits were determined to be 0.65, 0.28, 0.2 and 0.1 ppb for cadmium, lead, copper on Ir(Hg)UMEAs, and arsenic on AuUMEAs, respectively. Demonstration of the utility of the EMA was performed at four hazardous waste sites with ground water contaminated with various heavy metals, such as Pb, Cd, Cu, Zn and As.; Even though such microfabricated arrays are increasingly being used in electroanalysis, electron transfer kinetics have not previously been investigated. Therefore, a comparison of the results from electron beam evaporated and dc magnetron sputtered iridium surfaces was made to a polished metallic iridium electrode. Calculated heterogeneous electron transfer rate constants for ferricyanide and ferrocene indicate that the microfabrication techniques mentioned above provide nearly identical surfaces to that of a solid polycrystalline surface. |
