A pocket-size device for monitoring gaseous elemental mercury by passive sampling on a Nano-Au screen-printed electrode and detection by single drop smartphone-controlled voltammetry

Abstract

We report a novel strategy for decentralized monitoring of gaseous elemental mercury (GEM), Hg(0), in ambient air by a pocket-size low-cost analytical device. The essential components of the system are a gold nanoparticles-modified screen-printed carbon electrode (AuNPs-SPCE) for passive or active sampling by the amalgamation of mercury from the air and a miniaturized potentiostat (pen drive size). The potentiostat was connected to a smartphone for the determination of the amount of amalgamated Hg(0) during sampling, by voltammetry on a single 50 µL drop placed onto the AuNPs-SPCE. The method greatly benefits from the nano structuration of the gold electrode, providing a significant analytical improvement in terms of sensitivity and instrumental simplification, compared with a previously reported method based on a gold-sputtered screen-printed electrode. We report the exploration of the electrode surface by SEM, showing efficient adsorption on the nanoparticles due to the higher surface/volume ratio. Inter-electrode reproducibility using a set of three AuNPs-SPCE exposed to a GEM concentration of 5.78 ng dm−3 for sampling times from 0 to 360 min gave an average RSD of 16%. Passive and active sampling gave a similar performance for sampling times higher than 60 min. After 10 min passive sampling, the calibration gave adequate determination coefficients (R2 = 0.990) for the range 5.88–56.39 ng dm−3, with a detection limit of 2.41 ng dm−3. A high sensitivity calibration using 180 min passive sampling for the range 0.23 – 5.69 ng dm−3 of GEM gave R2 = 0.986, with a detection limit of 0.24 ng dm−3.