Shel lab BACTRON300, Installation And Operation Manual, Page: 33 / 86

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OPERATION
T
HEORY OF
O
PERATION AND
M
AJOR
C
OMPONENT
F
UNCTIONS
Achieving Anaerobic Conditions
No
Oxygen
Hydrogen
Positive
Pressure Active
Catalyst
Figure 6: Atmosphere Control Measures
The BACTRON workstation is designed to establish and maintain an anaerobic atmosphere
suitable for clinical cultivation of anaerobic bacteria. This atmosphere is initially achieved through a
purge of the workspace chamber using a flow of anaerobic mixed gas (AMG). This pushes normal
atmosphere out through the right arm port, with the door slightly ajar. Subsequent maintenance of
the chamber atmosphere is achieved with injections of AMG, and a resultant catalytic reaction
between the AMG hydrogen, any free oxygen, and the activated palladium of the chamber catalyst
scrubber. This reaction captures the oxygen in the formation of water vapor (H
2
O).
Each palladium catalyst must be kept clean and active by baking the catalyst cartridge at 200°C for
8 hours after every 24 hours of usage.
Additionally, the BACTRON is programmed to maintain a mild overpressure in the chamber to
prevent the infiltration of external atmosphere, including the diffusion of molecular oxygen through
seals.
The presence of oxygen in the workstation is detected through the use of color-changing Oxoid
brand indicator strips. Microbiological controls such as
Clostridium novyi or Pseudomonas
aeruginosa, may also be used to indicate anaerobic or aerobic conditions. Use of an optional,
activated carbon scrubber in the chamber helps absorb volatile fatty acids and hydrogen sulfides
generated by cultivation processes or other applications.
Condensation Management
Sample media evaporation from Petri dishes and water vapor from the catalytic reaction is trapped
on the cold plate of a Peltier-effect condensate chiller located behind catalyst cartridge. Condensed
moisture is then channeled into a drain tube that empties into a receptacle placed in the workspace
chamber by the end-user. The receptacle must be drained regularly. The Peltier condensate chiller
eliminates the need to use chemical desiccants, which can retain condensate and dry out culture
media.