Smartphone Nano-Colorimetry for On-Demand Multiplex Lead and Mercury Detection and Quantitation in Drinking Water

Mobile low-cost analytical systems for the detection and quantitation of heavy metal contaminants such as lead (Pb
²⁺
) and mercury (Hg
²⁺
) in drinking water are critical in preventing the general population from exposure to the toxic metal ions. In this paper, we presented smartphone nano-colorimetry (SNC) as a new technique for multiplex-sensing of dissolved Pb
²⁺
and Hg
²⁺
. The sensing mechanism of SNC is based on the microscopic dark-field imaging of micro-or nanoscale sediments of yellow lead chromate (PbCrO4) and red mercury iodide (HgI2) on a glass-PDMS substrate, followed by intensity analysis to quantitatively measure the concentration of Pb
²⁺
and Hg
²⁺
in the water. We showed that SNC capable of detecting and quantitating Pb
²⁺
and Hg
²⁺
below the EPA action level for both metal ions at 15 ppb and 2 ppb, respectively. We envision that SNC will realize highly sensitive and rapid in-field quantitation of toxic heavy metal contaminants in drinking water, enable citizens to examine their water on-demand for better life-quality.