Monitoring of Electrochemically Inactive Compounds by Amperometric Toxic Gas Sensors

摘要

A sample of 200 ppM benzene in air was circulated at rate of 10 mL/min past a heated 0.01-cm diameter platinum filament and then past a platinum-black sensing electrode potentiostated at 1.2 V versus RHE (reversible hydrogen electrode) in a 30 weight-% sulfuric acid electrolyte. The current through the electrode increased as the filament temperature was increased to about 600 exp 0 C. Sensing electrodes made of vapor-deposited platinum or platinum-gold alloy on porous polytetrafluorethylene yielded proportionately similar responses, whereas no significant response was obtained under the same conditions with a powdered gold sensing electrode. The room-temperature responses to various test compounds of the four sensing electrodes were measured at electrode potentials ranging from 0.9 V to 1.4 V versus RHE, with and without the heated platinum filament. The following ten compounds were tested: cyclohexane, chloroform, tetrachloroethylene, acetic acid, benzene, nitrobenzene, pyridine, benzyl chloride, ethyl acrylate, and tetrahydrofuran. Only the last two compounds elicited significant responses without the filament. However, with the filament heated to about 600 exp 0 C, each of the tested compounds elicited significant responses under different conditions. (ERA citation 09:023501)