Carbon screen-printed electrodes modified by a polycatechol film for Cu and Pb detection in acidified drinking water

The dissolution of metals such as Cu or Pb in water can be increased by prolonged stagnation of water in internal pipes of drinking water networks, resulting in high concentrations in the consumer's tap water. As they can accumulate in biota and affect living organisms with more or less serious long-term toxic effects, the monitoring of Cu or Pb in tap water and more generally in aquatic environments is therefore an important issue. For this purpose, a new electrochemical sensor based on a screen-printed carbon electrode modified with a polycatechol film was developed for the highly sensitive detection of Cu and Pb in drinking water. The electropolymerisation was first optimised to obtain a homogeneous and reproducible film for the detection of trace metals. The mechanism of the polymerization process was proposed and discussed. Then, the performance of the new sensor was evaluated. The pH and the conductivity were found to be the main parameters influencing the sensitivity of the sensors. Thus, the electrochemical analyses carried out at pH values around neutrality with this device made it possible to determine the free and labile forms of metal in solution, while the total metal contents were determined after acidification of water samples to pH 5 or less. Furthermore, a stable signal was obtained from 470 & mu;S cm- 1, which means that most of freshwater rivers and mineral waters can be directly analysed without any supporting electrolyte addition. After optimisation of the analytical conditions, a sensitivity of the order of & mu;g L-1 was reached for a deposition time of 60s while an electrodeposition time of 300s gave a sensitivity of ng L-1.