Interferences of various gases on porous glass-based formaldehyde sensors

In order to examine the influences of various gases on sensor elements developed recently for the detection of gaseous formaldehyde, experiments were made in which the elements were exposed to air including one of the test gases. The elements are made of a porous glass sheet in which beta-diketone (acetylacetone or 1-phenyl-1,3-butanedione) and ammonium ion are impregnated and both of the elements turn yellow from colorless upon exposures to formaldehyde. The experiments were made under a concentration of 2000 ppm and a 50% relative humidity. As a result, aromatics such as benzene, toluene and ethylbenzene were found to cause no color changes. On the other hand, aldehydes and compounds having one or more C-C double bonds turned the two elements yellow. However the effects of these compounds are expected to be negligible under the realistic conditions, in view of the facts that the values of absorbance of light at peak wavelengths for these compounds were small and that the concentrations of the gases tested in this study were several orders of magnitude higher than those in the real atmosphere, even in the indoor environment.