In most college chemistry laboratories, few gas-sampling tests are performed because the gas-sampling devices are complicated and costly. However, gas sampling is an important skill not only for students in chemistry and biology but also for students in toxicology and geology (1). It is essential for

A novel, simple, and small synchronous fluorescence and absorbance device in conjunction with a homemade passive gas sampler for the determination of formaldehyde in ambient air is described. A purple-blue light LED is used as light source, and two perpendicular photoresistors are applied to measure absorbance and fluorescence, respectively. An absorbing reagent, which consisted of a 2,4-pentanedione, ammonium acetate, and acetic acid solution, is enclosed in the sampler and used to collect and react with airborne formaldehyde. The reaction product, yellow 3,5-diacetyl-1, 4-dihydrolutidine, is then detected by the synchronous fluorescence and absorbance detectors. The light intensity is inversely proportional to the resistance of the photoresistor. The proposed device has been successfully applied to the determination of formaldehyde at various sites.