A passive tube-type sampler for the determination of formaldehyde vapours in museum enclosures

Abstract

A tube-type passive sampling method has been developed and assessed for the quantification of formaldehyde (methanal) 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 vapours in a Palmes diffusion tube containing a paper support impregnated with an acidified solution of 2,4-dinitrophenylhydrazine (2,4-DNPH). After sampling, quantification of the trapped F-DNPH is achieved by high performance liquid chromatography (HPLC) analysis with UV detection at 350nm. To validate the procedure, permeation devices were used to generate formaldehyde-containing atmospheres, 81–2975ppb, in a 20dm³ 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 27mg.ml^?1 solution of 2,4-DNPH which contained 4·5%v/v orthophosphoric acid. At 55% RH, and with low airflow in the chamber, the experimentally derived sampling rate of 1·34 ± 0·17ml.min^?1 was in good agreement with the theoretically derived sampling rate of 1·36ml.min^?1 The passive sampling method was repeatable and reproducible with RSD (relative standard deviation) values below 7%for long-term exposures at low air velocities.