| In this dissertation, a lab-on-a-chip sensor was developed for the detection of heavy metals for public health applications in two complex sample matrices. Specifically, zinc (Zn) was measured in blood serum, a highly relevant biomedical sample medium, while lead (Pb) and cadmium (Cd) were measured in root exudates, a relevant sample medium in environmental applications. These conventional analytical methods of measuring these metals (AAS and ICPMS) pose a number of critical challenges, including the time delay from sample collection, shipment to a certified metals laboratory and reporting results. The laboratory costs of such analysis can be high. Thus, there is a need for a low-cost point-of-care (POC) system that can provide these measurements in minutes.;The developed sensor consists of a three-electrode system, with an environmentally-friendly bismuth working electrode, a Ag/AgCl reference electrode, and a Au auxiliary electrode. The bismuth working electrode was used as opposed to the conventional mercury electrodes due to its non-toxic nature and comparable negative detection window. Optimizing the sensor layout, electrode area and the working electrode surface substantially reduced the hydrolysis effects and widened the potential window to the -0.3 to -1.9 V range (vs. Ag/AgCl reference electrode), which is more negative as compared to other electrodes such as Au, Pt, or carbon. Conditions critical to sensing, including preconcentration potential, preconcentration time, and buffer pH, were optimized. For detection of Zn, the sensor was successfully calibrated in the physiologically relevant range of 5 muM to 50 muM and has a limit of detection of 6 muM. The sensor was also successfully demonstrated to measure Pb and Cd in the range of 1 muM to 50 muM with limits of detection of 71 nM and 2.417 muM, respectively. With further development and integrated sample preparation, the sensor may be converted into a POC platform for monitoring heavy metals in blood or on-site monitoring of environmental samples. |
