A diffusive sampling device for the determination of formaldehyde in air using N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) as reagent

A new method utilizing the diffusive sampling of formaldehyde in air has be en developed. Formaldehyde is sampled with the use of a glass fiber filter impregnated with N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) and phosp horic acid. The formaldehyde hydrazone formed is desorbed from the filter w ith acetonitrile and determined by high-performance liquid chromatography ( HPLC) with UV/visible detection at 474 nm. The sampling rate was determined to be 24.7 mL min(-1) with a relative standard deviation of 7% for 48 expe riments. The measured sampling rates were not dependent on the formaldehyde concentration (0.1-1.0 mg m(-3)), sampling time (15-482 min) or relative h umidity (20-85%). The detection limit was 70 mu g m(-3) for a 15 min sampli ng period and 2 mu g m(-3) for an 8 h sampling period.