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 been developed. Formaldehyde is sampled with the use of a glass fiber filter impregnated with N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) and phosphoric acid. The formaldehyde hydrazone formed is desorbed from the filter with 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 experiments. 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 humidity (20-85%). The detection limit was 70 mu g m(-3) for a 15 min sampling period and 2 mu g m(-3) for an 8 h sampling period.