Fluorescence Determination of Low Formaldehyde Concentrations in Air by Dye Laser Excitation

This paper describes a fluorescence technique for the detection of sub-ppm-concentrations of formaldehyde in air at atmospheric pressure. The aldehyde is excited by a frequency doubled tunable dye laser covering the 320-345-nm wavelength range. The fluorescence intensity, measured at right angles through a 400-nm cutoff filter, is proportional to the formaldehyde concentration in air. Interferences by NO(2) and SO(2) are negligible. The detection limit of the system is 5 pphm at present, in good agreement with an estimate of the fluorescence yield in 1 atm of air. A considerable increase of the sensitivity is possible, and the use of this technique for measuring formaldehyde in ambient air in the ppb concentration range is projected.