Application of new sol–gel electrochemical sensors to the determination of trace mercury

The aim of this work was the synthesis and characterization of new modified sol–gel carbon composite electrodes and their application to the determination of trace mercury species with positive charge. Two types of modified electrodes were synthesized, sol–gel and sol–gel-PVSA carbon composite electrodes. In the last ones, poly(vinylsulfonic acid) (PVSA) was used as a functional polymer entrapped within the sol–gel material due to its cationic exchange properties. In a first stage, parameters affecting both, the sol–gel process and the electrode preparation were optimized. In a second stage, usefulness of developed electrodes applied to the determination of cationic mercury species was evaluated, optimizing the activation, preconcentration, measurement and regeneration steps. Developed electrodes showed very favourable electroanalytical properties for their use as amperometric sensors, such as small size, low cost, simple fabrication and handling, renewability and reusability. By means of an easy and low-cost methodology, satisfactory experimental results were obtained in Hg2+ determination. In this sense, developed analytical methodology showed adequate response times, linear concentration range up to three orders of magnitude (from 5.0 × 10−8 to 5.0 × 10−5 M) and detection limits of 1.5 × 10−8 M (3.0 μg L−1). These results suggest that the incorporation of different receptor molecules at the sol–gel carbon composite material in combination with a selected electrochemical reaction could improve the detection limit achieved and obtain electrochemical sensors adapted to the determination of different species of mercury and other heavy metals.