Amperometric detection of gaseous ethanol and acetaldehyde at low concentrations on an Au-Nafion electrode

An amperometric sensor capable of detecting mixtures of ethanol and acetald ehyde in the low ppb range without the need for prior separation is describ ed. The electrochemical cell was based on a Au sensing electrode chemically deposited onto one side of a Nafion membrane with 1 M NaOH internal electr olyte solution. The detection was achieved by applying two potentials, -450 and -290 mV vs. a saturated mercury-mercurous sulfate electrode (MSE), at which ethanol and acetaldehyde react at different rates. Under the conditio ns investigated, acetaldehyde oxidation was mass transport limited at both potentials, whereas the anodic current due to the oxidation of ethanol was 40% lower at the more cathodic potential. Detection limits of 2 and 1 ppb ( S/N = 3) were determined for ethanol and acetaldehyde respectively when the analyte species were detected individually. Poisoning of the working elect rode was not observed for concentrations of ethanol in the ppb range. Aceta ldehyde oxidation was found not to affect the sensing electrode condition, even at concentrations of several tens of ppm.