Renewable liquid film-based electrochemical sensor for gaseous hydroperoxides

Electrochemical sensors for hydroperoxides based on thin flowing films were investigated. The sensor is composed of two segments of Nafion tubing put on a silver wire. A small portion of the silver wire is exposed and is chloridized to function as the reference electrode. One Nafion segment has a Pt-wire coil wrapped on it to function as the counter electrode and the other has a similar Pt-Rh wire coil that functions as the working electrode. A collection solution flows as a thin film on the sensor surface and also functions as the collection medium. Hydrogen peroxide and cumene hydroperoxide were examined as test compounds. The former can be oxidatively determined with a Pt-Rh electrode over a large range (ppb-ppm) without any significant influence of relative humidity. By using a technique to stop the liquid flow, the sensitivity can be further improved. Cumene hydroperoxide, an industrially important hydroperoxide, can be determined easily with a relative precision of better than 5% in the vapor phase over simulated process reaction mixtures containing percentage levels of the analyte by reduction on a Pd electrode. The sensor is simple and inexpensive to fabricate and requires only a suitably equipped personal computer for operation.