We have developed a sensor element for detecting formaldehyde using a reaction between β-diketone and formaldehyde. We estimated the formation and decomposition reaction rate constants of pyridine derivatives (yellow dye) on the sensor element, and also estimated interference gases. We found that the formation reaction rate constant on acetylacetone sensor element was three times than that on 1-phenyl-1, 3-butandione's one, and absorbance was 2.4 times than that of 1-phenyl-1, 3-butandione's one. It means that the color of the acetylacetone element rapidly changes to deeper yellow when it is exposed to formaldehyde. The decomposition reaction occurs on the acetylacetone sensor element, on the other hand, only the formation reaction occurs on the 1-phenyl-1, 3-butandione element, and the pyridine derivative is stable at least for one week. Therefore it was found that the 1-phenyl-1,3-butandione and acetylacetone elements were suitable for long hours measurement and short hours measurement, respectively. We also found that no interference gases existed in the normal atmospheric condition.
The developed sensor element was small, flat plate, pumping-free, and accumulated type, therefore we could set that at the desired space where we wanted to know the formaldehyde concentration, for arbitrary period. Then the absorbance change of the sensor element could be converted into the formaldehyde concentration using the preliminarily calculated calibration curve.
We successfully measured the formaldehyde concentration in closed space, because the developed sensor worked without a pumping unit.
