Colorimetric determination of mercury vapor using smartphone camera-based imaging

The smartphone camera presents a convenient, portable, and low-cost innovation in colorimetric measurements. In this paper, a smartphone camera was applied for the colorimetric detection of gaseous elemental mercury, an atmospheric pollutant of concern in environment, and workplace monitoring. A cuprous iodide (CuI)/polystyrene composite was used as the recognition element, which exhibited a reddish color in the presence of Hg⁰. Digital images of the sensing reagent phase were captured by a smartphone camera and were analyzed in red–green–blue color space using ImageJ, an open source image processing program. Parameters for the digital colorimetric sensing including the color values, polymer reagent binder, amount of CuI, exposure time, and Hg⁰ concentration were investigated and optimized. The linear working range of the sensor was from 61 to 270?μg/m³ Hg⁰ with a correlation coefficient of 0.978. The limit of detection is 16?μg/m³ Hg⁰. This method shows the feasibility of applying a smartphone camera for a simple, reliable, and inexpensive colorimetric measurement of Hg⁰ vapor in a gas mixture such as air.