A diffusion tube sampler for the determination of acetic acid and formic acid vapours in museum cabinets

Abstract

A passive, diffusion-tube sampler has been developed for the quantification of acetic acid and formic acid vapours in ambient air. The sampling rates of the diffusion tube and the response times were calculated to be 0.88 ml min −1 and 3.8 min for acetic acid and 1.02 ml min −1 and 3.3 min for formic acid, respectively. The sampler has been deployed unobtrusively in museum environments to collect pollutants over a period of typically 1–2 weeks. Determination of the collected analytes was performed using ion chromatography. Under laboratory test conditions, the results of the sampler for replicate analyses were found to be repeatable and reproducible; typical RSD values were less than 5% for the collection of acetic and formic acid vapours from atmospheres of approximately 187 and 88 mg m −3, respectively. Detection limits of 44 and 13 μg m −3 were calculated for a two week sampling period for acetic acid and formic acid, respectively. The mass of acids collected by the passive sampler increased linearly with atmospheric acid concentrations up to approximately 386 mg m −3 acetic acid and 194 mg m −3 formic acid. In an atmosphere containing approximately 187 and 88 mg m −3 of acetic and formic acid vapours, respectively, the mass of acids collected by passive samplers increased linearly for exposure times between 2 and 75 h. The sampler has been used to investigate the concentration of acetic acid and formic acid vapours in museum cabinets where damage to artefacts by atmospheric pollution has been observed.