Amperometric Detection of Gaseous Formaldehydein the ppb Range

Abstract

The direct amperometric detection of low levels of formaldehyde in the gas phase with an acidic electrochemical cell based on a gold coated Nafion membrane as working electrode was investigated. The sensor was found to show a linear response from the detection limit of 13 ppb up to at least 10 ppm. Influences of the flow rate and the humidity of the gas stream were studied. Also determined were the cross-sensitivities to a number of organic and inorganic gases. A new approach to overcome the interferences from NO, NO2 and SO2 is proposed whereby formaldehyde is selectively adsorbed from the sample stream with an aluminum oxide filter. By forming the difference for the measurements with and without filter a net signal for formaldehyde could be obtained in presence of the interferants.