Characterisation of particle collection and transmission in a polydimethylsiloxane based denuder sampler.

Denuder sampling devices consisting of two multi-channel silicone rubber traps separated by a quartz fibre filter, have been effectively employed for the simultaneous sampling of gas and particle associated semi-volatile organic compounds. Here controlled laboratory experiments were conducted to further elucidate the fundamental operating mechanisms of this portable denuder with respect to particle transmissions. Particle collection efficiency of the quartz fibre filters as well as particle transmission efficiency through the silicone rubber traps using ambient aerosol and aqueous suspensions of monodisperse polystyrene latex (PSL) as test particles (0.3, 0.5 and 0.8 mu m), were evaluated for various scenarios. Particle size and number concentration were measured with a scanning mobility particle sizer. Transmission efficiency of the denuder was determined from the ratio of particle concentration transmitted by the denuder to that of a bypass line. All sizes of PSL particles were collected with high efficiency and reproducibility by the quartz fibre filter ( > 98% with variation coefficients < 16%). Overall transmission efficiencies for all particles > 100 nm ranged from 91% to 100% (variation coefficients of 2-14%). Transmission efficiencies decreased when PDMS tubes were twisted but were not significantly different for traps made by different individuals. Ambient particles, which were studied for the first time, were collected with 88-95% collection efficiency. Losses of smaller particle size fractions in the trap portion of the denuder were likely due to diffusion and electrostatic effects. The high particle collection and transmission efficiencies of all tested particle sizes indicated that these denuders are very effective tools for aerosol measurements