Carbon Nanotube Based Flow-Through Electrochemical Cell for Electroanalysis.

A flow-through electrode made of a carbon nanotubes (CNT) film deposited on a polytetrafluoroethylene (PTFE) membrane was assembled and employed for the determination of low concentration of copper as a model system by linear sweep anodic stripping voltammetry (LSASV). CNT films with areal mass ranging from 0.12 to 0.72 mg cm-2 were characterized by measurement of sheet resistance, water permeation flux and capacitance. Moreover, CNT with two different sizes and PTFE membrane with two different pore diameters (0.45 and 5.0 μm) were evaluated during the optimization of the electrode. Thick layers made of small CNT exhibited the lowest sheet resistance and the greatest analytical response, whereas thin layers of large CNT had the lowest capacitance and the highest permeation flux. Electrodes made of 0.12 mg cm-2 of large CNT deposited on 5.0 μm PTFE enabled sufficiently high mass transfer and collection efficiency for detecting 64 ppt of Cu(II) within 5 min of deposition and 4.0 mL min-1 flow rate. The analytical response was linear over 4 orders of magnitude (10-9 to 10-5 M) of Cu(II). The excellent performance of the flow-through CNT membrane integrated in a flow cell makes it an appealing approach not only for electroanalysis, but also for the electrochemical treatment of waters, such as the removal of low concentrations of heavy metals and organics.