Carbon nanotube-based electrodes for detection of low-ppb level hexavalent chromium using amperometry

Carbon nanotube (CNT)-based electrodes, prepared using a printable technique,were investigated for the electrochemical detection of hexavalent chromium (Cr(VI)). CNT pastes were coated onto paper substrates and commercially available screen-printed electrodes and used as amperometric sensors for Cr(VI). The CNT electrodes showed electrochemical current responses as high as 500 nA/ppb Cr(VI) and limit of detection as low as 5 ppb when a large area electrode was used. The CNT-modified, screen-printed electrodes showed good selectivity to Cr(VI) and were effective for quantifying the Cr(VI) levels in cooling tower blowdown water. A selective H₂O₂ reduction technique was also applied to Cr(VI) detection and integrated into amperometric detection in a flow cell. These studies show that CNT-based electrodes can be promising for field applications and real-time monitoring of low-level Cr(VI) in power plant waters.