Andersen sampler
An Andersen sampler or Andersen impactor is a cascade impactor used to determine the amount of viable pathogens in a given area, in particular bacteria and fungi. Unlike real-time electronic particle counters, the Andersen sampler imparts pathogens on petri dishes, which require incubation. Thus, calculation of the contaminated air requires working backwards from the resulting pathogen growth in each dish.
Andersen samplers have been used to assess the nature of pathogenic aerosols in various scientific papers, like the continued aerosolization of anthrax following attacks in 2001.[1]
Operation
[edit]
Andersen's paper from 1958 describes a six-stage Andersen sampler that counts "viable airborne particles". In each stage, air goes through specifically sized holes, past a petri dish that aerosols impact, before subsequently moving through smaller holes towards the other petri dishes. Each stage gradually increases the velocity of the air; the sampler relies on inertia for particles to leave the air stream.[2]
Calculation of the number of viable particles is normally done by counting colonies via a microscope, termed the "microscope method" in Andersen's paper. For stages 3-6, Andersen provides an alternate means of calculating viable particles via the "positive hole method". The method involves counting the number of colonies from a macroscopic point of view; each visible colony corresponds to a hole in each stage of the Andersen sampler. A conversion table is then used to quickly calculate the number of viable particles.[2]
History
[edit]Information on the development of the Andersen sampler was initially classified by the US army, but is declassified as of January 24, 1958.[3] A noted early use of the Andersen sampler was the tracking of disease in the states of Oregon and California.[4]
An assessment of the Andersen Mark-II cascade impactor was published in 1988.[5]
In 2012, a comparison was made between the "culturable particles" (CP) method and the "culturable organisms" (CO) method with the help of an Aerodynamic Particle Sizer (APS). The distributions between the CP and CO method were different enough for the null hypothesis to be rejected; the authors suggest that this may be due to the higher resolution particle count afforded by the APS, the Andersen sampler's wall losses, or the unintended collection of smaller particles in the earlier stages.[6]
In 2013, a group of researchers improved the collection efficiency of the Andersen sampler by adding mineral oil to the petri dish agar. Results were supported through the use of an optical particle counter.[7]
See also
[edit]- Cascade impactor – Graduated method of aerosol measurement and collection
- Aerosol impaction
- Particulate matter sampler
- Bioaerosol
- Particle counter
References
[edit]- ^ Weis, Christopher P. (2002). "Secondary Aerosolization of Viable <EMPH TYPE="ITAL">Bacillus anthracis</EMPH> Spores in a Contaminated US Senate Office". JAMA. 288 (22): 2853–2858. doi:10.1001/jama.288.22.2853. PMID 12472327.
- ^ a b c Andersen, Ariel A. (1958). "New Sampler for the Collection, Sizing, and Enumeration of Viable Airborne Particles". Journal of Bacteriology. 76 (5): 471–484. doi:10.1128/jb.76.5.471-484.1958. PMC 290224. PMID 13598704.
- ^ "Air 'Sampler' at Dugway Aids Studies". The Salt Lake Tribune. 1958-01-24 – via newspaperarchive.com.
- ^ "Provoan Develops Air Pollution Study Instrument". Utah Provo Daily Herald. 1958-01-26 – via newspaperarchive.com.
- ^ Mitchell, J.P.; Costa, P.A.; Waters, S. (1988). "An assessment of an andersen mark-II cascade impactor". Journal of Aerosol Science. 19 (2): 213–221. Bibcode:1988JAerS..19..213M. doi:10.1016/0021-8502(88)90224-8.
- ^ King, Maria D.; McFarland, Andrew R. (2012). "Use of an Andersen Bioaerosol Sampler to Simultaneously Provide Culturable Particle and Culturable Organism Size Distributions". Aerosol Science and Technology. 46 (8): 852–861. Bibcode:2012AerST..46..852K. doi:10.1080/02786826.2012.669507.
- ^ Xu, Zhenqiang; Wei, Kai; Wu, Yan; Shen, Fangxia; Chen, Qi; Li, Mingzhen; Yao, Maosheng (2013). "Enhancing Bioaerosol Sampling by Andersen Impactors Using Mineral-Oil-Spread Agar Plate". PLOS ONE. 8 (2): e56896. Bibcode:2013PLoSO...856896X. doi:10.1371/journal.pone.0056896. PMC 3584084. PMID 23460818.
Further reading
[edit]- Gillespie, V.L.; Clark, C.S.; Bjornson, H.S.; Samuels, S.J.; Holland, J.W. (1981). "A comparison of two-stage and six-stage Andersen impactors for viable aerosols". American Industrial Hygiene Association Journal. 42 (12): 858–864. doi:10.1080/15298668191420819.
- Solomon, William R. (1970). "A simplified application of the Andersen sampler to the study of airborne fungus particles". Journal of Allergy. 45 (1): 1–13. doi:10.1016/0021-8707(70)90012-2. PMID 5262360.
- Greene, V. W.; Vesley, D. (1962). "Method for Evaluating Effectiveness of Surgical Masks". Journal of Bacteriology. 83 (3): 663–667. doi:10.1128/jb.83.3.663-667.1962. PMC 279325. PMID 13901536.