Janus Electrochemical Paper-Based Analytical Devices for Metals Detection in Aerosol Samples

Exposure to trace metals in airborne particulate matter (PM) has been linked to various adverse health effects. Quantifying metals in PM is important; however, current analytical tools tend to be bulky and expensive. A need therefore exists for more rapid, low-cost, portable tools for multiplexed determination of metals in PM. Electrochemical paper-based devices (ePADs) have been used for detecting metals in PM but require different devices and methods for different metals, making the systems more complicated than desired. Recently reported Janus ePADs offer a solution to this problem by allowing for multiple electrochemical experiments from a single sample. Here, we sought to determine if a Janus ePAD containing four independent channels and working electrodes could be used for simultaneous detection of multiple metals in PM. Online sample pretreatment in each channel during sample delivery yielded optimal conditions for each experiment. The design allows the device to conduct square-wave anodic stripping voltammetry (SWASV) and square-wave cathodic stripping voltammetry (SWCSV) for simultaneous detection of Cd, Pb, Cu, Fe, and Ni from a single sample. Two detection zones each with shared reference and counter electrodes were used for SWASV and SWCSV, respectively. The proposed sensors reached LODs down to 0.5, 0.5, 1.0, 0.5, and 1.0 μg L^-1, for Cd(II), Pb(II), Cu(II), Fe(II), and Ni(II), respectively. The linear working ranges were 0.5-400.0 μg L^-1 for Cd(II), Pb(II), and Fe(II), 1.0-400.0 μg L^-1 for Cu(II), and 0.5-200.0 μg L^-1 for Ni(II). The devices were applied for Cd(II), Pb(II), Cu(II), Fe(II), and Ni(II) determination in PM samples, and the results agreed with those using traditional ICP-MS analyses at 95% confidence.