Rapid Detection of Toxic Heavy Metals with Boron-Doped Diamond Sensors

Toxic heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg) cause serious health complications and ingestion of these toxins through contaminated drinking water, even at trace levels, has become a prominent issue. Chronic exposure to toxic metals such as Pb, Cd, and Hg is carcinogenic while causing other problems like kidney failure, severe neurotoxicity, and IQ loss. These problems are only magnified in children as several stages of bodily development can be severely hindered. Electroanalytical methods are an attractive technique for trace detection of heavy metals due to low cost of experimental tools, low limits of detection, multi-element analysis capability, and the possibility to package them into sensing devices. Specifically, boron-doped diamond (BDD) is a rugged, yet sensitive electrode material with significant potential in electrochemical sensing. Using square-wave stripping voltammetry (SWSV), we have developed BDD micro-electrode arrays (MEAs) as well as macro-electrode disks, achieving detection limits as low as 200 parts-per-trillion (ppt) for Pb with a deposition time of just 2 minutes. This is nearly 100x below the 15 ppb maximum contaminant level (MCL) in drinking water set by the Environmental Protection Agency (EPA). MEAs of various diameter and spacing were investigated to find the optimum geometry for both single and multi-element detection of Pb, Cd, Hg, Cu and Mn where results were compared with those obtained at various macro-electrode sizes. Additionally, pen-like sensors incorporating the optimized BDD working electrode, a BDD reference electrode, and BDD counter electrode were constructed and used for the detection of the aforementioned metal ions. Long-term stability of the BDD quasi-reference electrode was investigated in detail. The applicability of all electrode constructions for the detection of metal ions in drinking and environmental water samples were studied for rapid detection at home or in the field. Figure 1