Bioelectronic sniffers for formaldehyde in the gas phase

Abstract

Two kinds of enzyme electrodes were constructed by immobilizing ALDH or FALDH into a Pt-electrode deposited onto a hydrophilic-polytetrafluoroethylene membrane. A bioelectronic sniffer device for formaldehyde vapor was fabricated by incorporating the enzyme electrode into the reaction unit with both gas- and liquid-compartments separated by a diaphragm membrane. The sensitive area of the electrode was placed onto the diaphragm membrane in the liquid compartment. Gaseous substances in the gas-compartment could diffuse to the electrode through the diaphragm. The amperometric current of the sniffer-device with ALDH and FALDH increased by applying formaldehyde vapor, thus obtaining the calibration range of 10–2000 ppb, including the maximum permitted concentrations (80 ppb) and the human detection limit (410 ppb). In comparison with the outputs obtained by applying other gaseous substances, the sniffer-device with biocatalysts, especially FALDH, indicated high gas-selectivity for formaldehyde vapor.