Microscale Voltammetric Mercury Monitor
DOE Phase I Contract No. DE-FG02-04ER83937
The Phase I program demonstrated feasibility for rational design of microband electrochemical detectors for dissolved mercury, Hg(I), Hg(II). Part-per-billion detection limits were obtained for several unique electrode configurations using anodic stripping voltammetry as the detection method. Experimental work carried out included development of methods to fabricate the microband electrodes, physical and electrochemical characterization of the microbands and investigation of basic analytical performance issues for Hg(I) and Hg(II), including detection limit and sensitivity, dynamic range, span and zero drift and effects of samples conditions such as ionic strength and pH on detection performance.
Microbands were prepared singly and in arrays with fingers 5 to 100 µm wide and 1 to 8 mm long. Arrays contained 2 to 212 individual elements. Voltammetric characterization with ferricyanide showed the expected microband behavior. Hg(II) monitoring was performed in a variety of complexing and noncomplexing acidic media. Hg(II) detection was accomplished with 0.78 to 16.6 ppb detection limits depending on the sample conditions. Long term span drift of the sensor was less than 2% at 10 ppb Hg(II).
Electrochemical detection of heavy metals provides a low-cost, portable means for on-site testing to support environmental evaluations. Technology to emerge from this program would have application in drinking water and waste water analysis, process effluent analysis and environmental remediation.