Sampled-current voltammetry on an electrode array for metallic trace elements detection in water – EASCVsens

Electrochemical techniques with specific electrodes, such as those based on the complexation of MTEs by molecules used as specific receptors, emerge as a credible alternative, as they are fast, low cost, robust and can lead to portable sensors. This project is based on recent advances in electrochemical analysis and surface functionalization developed by the research team to achieve a rapid, transportable analytical system for the selective analysis of ETMs (Pb2+, Hg2+, Cd2+) at trace level (1 to 10 µg/L) in aqueous media. In addition to the development of sensitive, selective and stable sensors able to perform ETM analysis on site, the aim of this project is to develop an original electroanalytical method that can be applied to many types of pollutants.

Electrochemical sensors were developed using a surface functionalization method, providing a generic platform for the immobilization of specific MTE receptors, including a robust, selective cadmium sensor with a limit of detection compatible with the application.

Key advances in the project also include the fabrication of a transportable potentiostat dedicated to the analytical method, and the development of an array of carbon or gold electrodes, each composed of several ultramicroelectrodes.

The project has led to the publication of several peer-reviewed scientific articles and oral communications in national and international conferences. The ultramicroelectrode arrays developed in collaboration with the Vmicro Company provide support for analytical electrochemistry beyond the scope of the project. A new product has been developed by the Origalys Company and will be marketed to meet various electrochemical needs.

Metallic trace elements are pollutants that are present in water naturally or because of mining, agriculture and industry. They are toxic even at trace level and so reliable analytical methods able to measure them on site are necessary. The most conventional methods used to quantify them are relatively expensive and generally require long analysis time associated with the difficulties to perform field analyses. Electrochemical methods using specific electrodes, as those based on ligands, are a low-cost and more and more credible alternative since they are fast and could easily be miniaturized to achieve portable sensors.
The final and applied goal of the project is the simplification of the metallic trace elements analysis in natural environment and so the ability to increase the amount of data for a given budget. It is intended to the achievement of an electrochemical analytical system that is fast and transportable allowing the selective analysis of metallic elements (Pb2+, Hg2+, Cd2+) at trace level (10-9-10-8 mol L-1) in aqueous medium (see and rivers) using recent advances in portable electrochemical analysis and surface functionnalization. In this active research field, the project combines original fundamental and applied aspects for the development of such sensors using i) a new concept of device based on sampled-current voltammetry performed on an electrode array (EASCV) allowing the renewal of the electrode surface and of the solution in the proximity of the electrode during the analysis. Since the data acquisition, that does not require the use of a potential ramp, is simplified, the device can be portable. ii) a good control of the functionalization process to introduce specific receptors (Strategy based on the electrografting of aryldiazonium associated to protection-deprotection steps). The adaptation of the electrochemical system based on EASCV to modified electrodes will be performed for the first time in this project. An improvement of the electrochemical response compared with a classical analysis performed on a single electrode is expected since the electrochemical signal on each electrode of the array is independent of the others.
Using the combined expertise of the four partners, we will achieve an efficient and cost-effective analytical tool by the covalent immobilization of specific receptors on electrode array associated with anodic stripping EASCV analysis. The development of the sensors for real conditions and their evaluations will be a major part in the project that will be performed according to the following tasks.
1) An electrode array compatible with EASCV will be made and modified by a well-controlled functionnalization process to introduce receptors specific to each ion.
2) The optimization of the analytical conditions for metallic trace elements detection by sampled current voltammetry on a modified electrode array will be performed with test solutions. The recycling ability of the sensor will be evaluated.
3) The performances of the sensor using simple matrices and a laboratory multipotentiostat will be established. The interferences and the ability of the sensor to work in complex medium will be assessed.
4) An important point will be the validation of the transportable electroanalytical system dedicated to EASCV. This step will lead to the component validation in laboratory environment.
5) The last step will be dedicated to the validation of the electroanalytical technology in relevant environment. The objective is a better knowledge of the constraints linked to the implementation of the analytical system on real sites.