Lab-on-a-chip sensor for detection of highly electronegative heavy metals by anodic stripping voltammetry

This work describes development of a lab-on-a-chip sensor for electrochemical detection of highly electronegative heavy metals such as manganese and zinc by anodic stripping voltammetry. The sensor consists of a three-electrode system, with a bismuth working electrode, a Ag/AgCl reference electrode, and a Au auxiliary electrode. Hydrolysis at the auxiliary electrode is a critical challenge in such electrochemical sensors as its onset severely limits the ability to detect electronegative metals. The bismuth working electrode is used due to its comparable negative detection window and reduced toxicity with respect to a conventional mercury electrode. Through optimization of the sensor layout and the working electrode surface, effects of hydrolysis were substantially reduced and the potential window was extended to the -0.3 to -1.9 V range (vs. Ag/AgCl reference electrode), which is far more negative than what is possible with conventional Au, Pt, or carbon electrodes. The described lab-on-a-chip sensor for the first time permits reliable and sensitive detection of the highly electronegative manganese. The favorable performance of the bismuth electrode coupled with its environmentally-friendly nature make the described sensor attractive for applications where disposable chips are desirable. With further development and integrated sample preparation, the lab-on-a-chip may be converted into a point-of-care platform for monitoring heavy metals in blood (e.g., assessment of manganese exposure).