Monitoring of parts-per-billion levels of formaldehyde using a diffusive sampler

A diffusive sampler for formaldehyde originally designed for use in personal monitoring of worker exposure has been evaluated for static measurement of low formaldehyde levels in indoor air. The sampler consists of a 37-mm glass fiber filter impregnated with 2,4-dinitrophenylhydrazine and phosphoric acid and mounted in a polystyrene filter cassette. Formaldehyde is sampled by controlled diffusion and subsequent hydrazone formation on the filter. The hydrazone is eluted from the filter with acetonitrile and analyzed by liquid chromatography and a UV detector. The diffusive sampler was evaluated for static (area) sampling in several industries, offices, and homes with formaldehyde levels of 6-200 ppb. Results from diffusive samplers were compared with results from pumped samplers. Even at low wind velocities (less than 0.01 m.s-1) there was good agreement between pumped and diffusive samples. The sensitivity will be 1 ppb in a 24-h sample, making the sampler especially useful for indoor air monitoring of low formaldehyde levels.