Sensitive, Fast and Cheap Approach for the Electrochemical Monitoring of Pollutants in Water

Andrea Buffa, Institute of Chemistry, Hebrew University of Jerusalem, Jerusalem, Israel
Daniel Mandler, Institute of Chemistry, Hebrew University of Jerusalem, Jerusalem, Israel
Yigal Erel, Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel

A novel approach is proposed for significantly increasing the sensitivity of electrochemical detection of both organic and inorganic pollutants in water. In the present work the properties of multi walled carbon nanotubes (MWCNT) buckypaper, such as porosity, water permeability and electrical conductivity are exploited for preparing an ultrathin electrode whereby the analyte solution is pumped directly through the MWCNTs net while performing electrochemical or adsorptive deposition of the analyte.  This system promise to reduce considerably the time required for the determination of pollutants in water by anodic stripping voltammetry (ASV) since the mass transfer is determined by the speed at which the analyte solution is pumped through the electrode. The buckypaper porous layer is prepared by filtration of a stable MWCNTs dispersion through a PTFE filter membrane. The buckypaper membrane electrode has been installed in a syringe filter connected to a pumping system. Membrane made of MWCNTs with two different outer diameter have been characterized by measuring water permeability and sheet resistance and compared. While the sheet resistance of the two types of membranes is not significantly different, membranes made of MWCNTs with bigger outer diameter showed better water permeability that allows higher analyte velocity through the electrode. The deposition efficiency of the system has been evaluated by performing linear sweep ASV of Cu²⁺ 10^-5 M and it reached the promising value of 80% with sharp and clear stripping peaks. The system allowed the detection of 6.4 ppb of Copper in 30 seconds of deposition time and a maximum deposition efficiency of 50%. The optimization of the system will continue with a variety of inorganic and organic pollutants and natural water samples.