A tube-type passive sampling method has been developed and validated for the quantification of formaldehyde vapours in indoor air. The sampler was designed for use in museums where test sites often include small enclosures with low air movement. The procedure involves collection of formaldehyde vapour in a Palmes diffusion tube which contains a paper support impregnated with an acidified solution of 2,4-dinitrophenyl hydrazine (2,4-DNPH). After sampling quantification of the trapped hydrazone is achieved by high performance liquid chromatography (HPLC) analysis with UV detection at 350 nm. To validate the procedure, permeation devices were used to generate formaldehyde containing atmospheres, 81 to 2975 ppbv, in a 20 L chamber so that experimentally derived sampling rates could be calculated and compared with the theoretical value. Three 2,4-DNPH solutions were investigated to obtain an efficient and stable trapping solution. Best results were achieved with a 27.3 µg mL-1 solution of 2,4-DNPH which contained 4.5% v/v orthophosphoric acid and 2.7% v/v ethylene glycol dimethyl ether. At 55% RH and with a low air flow in the chamber, the experimentally derived sampling rate of 1.34 +/-0.17 mLmin-1 was in good agreement with the theoretically derived sampling rate of 1.36 mLmin-1. The passive sampling method was repeatable, and reproducible with RSD values below 7%. In environments with a higher air velocity, or at a lower relative humidity (5% RH), sampling rates of 1.24 +/-0.04 mLmin-1 and 1.18 +/-0.08 mLmin-1 respectively, were derived.
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© May 11th, 2000