Sampling and Retention Efficiencies of Batch-Type Liquid-Based Bioaerosol Samplers

Abstract

Four commercially available batch-type bioaerosol samplers, which collect time-integrated samples in liquids, were evaluated. Sampling efficiency was characterized as a function of particle size using near-monodisperse polystyrene spheres (sizes of 1-5 µm) and oleic acid droplets (3-10 µm). Results show the sampling efficiency of AGI-30 impingers range from 4-67% for particle sizes of 1 to 5.1 µm with significant variations between units; those of SKC BioSampler impingers range from 34-105% for particle sizes from 1 to 9 µm; those of a batch-type wetted wall cyclone with compensation for evaporation (BWWC-EC) range from 5 to 65% for particle sizes 1 to 10 µm; and, those of a batch-type wetted wall cyclone with no evaporation compensation (BWWC-NC) range of 55 to 88% for particle sizes of 1-8 µm. Retention efficiency was measured for 1 and 10 µm polystyrene spheres. For the AGI-30 and BWWC-EC, the retention efficiency of 1 µm particles after 1 h was less than 30%, while that of the SKC BioSampler was 59%. Due to liquid evaporation, the BWWC-NC could not be operated for 1 h. Retention efficiencies for Bacillus atrophaeus spores and Pantoea agglomerans vegetative cells were measured for the AGI-30 and the SKC BioSampler. Results for the spores were about the same as those for 1 µm non-viable polystyrene particles; however, the vegetative bacteria lose culturability and consequently show lower retention efficiencies. For the impingers, significant performance differences were observed in units delivered by vendors at different times.

Use of Medical Metered Dose Inhalers for Functionality Testing of Bioaerosol Detection and Identification Systems

“…The lower dose ratio values for the 1 µm PSL particles were likely a result of the greater adherence of those particles to the inner walls of the PDC. Kesavan et al (2010) observed a similar phenomenon with 1 µm PSLs in bioaerosol samplers that collected time-integrated hydrosol samples.…”

Diversity of airborne bacteria in samples collected using different devices for aerosol collection

“…If the composition of microorganisms in the sample stays the same as in the ambient air, the sampling efficiency is not all that important for determining microbial diversity as long as enough material can be collected for further analysis. However, different samplers also perform differently as a function of particle size (Kesavan et al 2010;King et al 2009). This is considerably more serious, since if the size of collected particles changes with sampling approach, the results will inevitably be affected since the diameter of airborne microorganisms can vary from tens of nanometers to one hundred micrometer (Wittmaack et al 2005).…”

“…However, the extant studies use various sampling approaches, which complicates the comparison of microbial communities, diversity, and ecology. While many studies have compared the sampling efficiency of different aerosol collectors (Fields et al 1974;Jensen et al 1992;Kesavan et al 2010;King et al 2009;Whyte et al 2007), no study, to the best of our knowledge, has addressed how the sampling strategy can affect apparent microbial diversity of air samples. Since different devices have different particle cut-off diameter, the choice of sampling technique may certainly affect the composition of the sampled community; let alone the most common bacteria may range in diameter from 0.1 to 5 lm, while airborne fungal spores and algae are typically 5-15 lm and may be as large 100 lm (Tormo et al 2001;Wittmaack et al 2005).…”

Use of an Andersen Bioaerosol Sampler to Simultaneously Provide Culturable Particle and Culturable Organism Size Distributions

“…Possible reasons for the lower concentration value measured with the impinger vis·a·vis the Andersen are greater wall losses in the impinger for some of the larger particles and a loss of both cells and culturability in the hydrosol during the collection period. The impinger has wall losses of about 35% for 7 µm AD particles (Kesavan et al 2010) as compared with about 10% losses in the Andersen for that same size (Rao and Whitby 1978). Kesavan et al (2010), in tests of SKC impingers that had Pantoea agglomerans (vegetative cells) spiked into the collection liquid, observed that about half of the cells were either lost to the impinger walls or rendered unculturable following operation of the impinger for 1 h subsequent to the spiking.…”

“…The impinger has wall losses of about 35% for 7 µm AD particles (Kesavan et al 2010) as compared with about 10% losses in the Andersen for that same size (Rao and Whitby 1978). Kesavan et al (2010), in tests of SKC impingers that had Pantoea agglomerans (vegetative cells) spiked into the collection liquid, observed that about half of the cells were either lost to the impinger walls or rendered unculturable following operation of the impinger for 1 h subsequent to the spiking. FAME bacteria isolate analyses, from a test in the classroom conducted subsequent to the primary sampling experiment, showed 6 strains in the proportions listed in Table 2.…”