A smartphone-based quantitative point-of-care testing (POCT) system for simultaneous detection of multiple heavy metal ions

It is of great significance to develop versatile and cost-effective point-of-care testing (POCT) systems for simultaneous quantitation of multiple analytes on-site. This work reports on: 1) the customized electrodes which exhibit good analytical performance for simultaneous detection of Cd2+, Cu2+, Hg2+, Pb2+ with low detection limits (Cd2+, 0.296 mu M; Cu2+, 0.055 mu M; Hg2+, 0.351 mu M; and Pb2+, 0.025 mu M) and wide dynamic ranges (Cd2+, 0.50-12.5 mu M; Cu2+, 0.10-9.50 mu M; Hg2+, 0.50-12.5 mu M; and Pb2+, 0.10-12.5 mu M) using differential pulse voltammetry (DPV) measurements. 2) a hand-held electrochemical analyzer which can realize two-way communication with a smartphone and implement DPV measurements; its cost, weight and power consumption are similar to$10.0, similar to 30 g and similar to 253 mW, respectively; 3) a self-developed APP DHMI which can control the analyzer, receive data from the analyzer, and plot the voltammograms on smartphone's screen in real-time. This quantitative POCT system has been successfully demonstrated for simultaneous quantitation of Cd2+, Cu2+, Hg2+, Pb2+ in tap water, mineral water and Pearl River water, and the quantitation results correlated well with ICP-MS measurements. The features of cost-effectiveness, ease-to-use and reliability make this quantitative POCT system useful for on-site monitoring of multiple heavy metal ions, especially in resource-constrained environments.