A polymer lab chip sensor with microfabricated planar silver electrode for continuous and on-site heavy metal measurement

This paper presents a reusable polymer lab chip sensor for continuous and on-site heavy metal monitoring in nature. In particular, detection of lead (Pb(II)), which is the most common heavy metal pollutant, has been performed using the proposed lab chip sensor. The miniaturized lab chip sensor consists of a microfabricated silver working electrode that replaces the conventional mercury and bismuth electrodes, an integrated silver counter and quasi-reference electrode, and microfluidic channels. The proposed sensor targets on-site environmental monitoring in a continuous fashion without disturbing or contaminating the sensing environment when it is reused. The reusability of the miniaturized lab chip sensor was characterized through forty-three consecutive measurements in non-deoxygenating standard solutions inside the microchannels using square-wave anodic stripping voltammetry (SWASV). With only 13.5 μL of sample volume the sensor chip showed a correlation coefficient of 0.998 for the Pb(II) concentration range of 1-1000 ppb with the limit of detection of 0.55 ppb at 300 s deposition time. The peak potentials during the forty-three consecutive SWASV measurements showed a relative standard deviation of 1.0%, with a standard deviation of 0.005 V. The high repeatability and linearity of the sensor over the large, three orders of magnitude, dynamic range of 1-1000 ppb showed that the developed sensor chip can be reused for a variety of on-site measurements such as for soil pore water or groundwater, using only micro-volumes.