Friday, February 24, 2017

Anaerobic Chambers for Biological Applications - Some Basics

anaerobic chamber with airlock and incubator
Vinyl anaerobic chamber, Type A.
One of many variants manufactured
by Coy Lab Products
Anaerobic chambers are used in life science research to study microbial life that thrives in environments with very little or no oxygen. The essential arrangement includes an environment enclosure, transfer airlock, gas exchange system, sample handling means (usually gloves integrated into the enclosure),and a scrubber for removing trace oxygen from the chamber interior. Other fixtures and accessories can customize an anaerobic chamber for particular use, and might include shelves, storage cabinets, or incubator chambers.

Maintaining good environmental performance from an anaerobic chamber calls for attention to various seals and other mechanical features that are essential to proper operation and subject to normal wear and tear. Below, in question and answer form, are some basics for understanding and using a Coy anaerobic chamber (excertped from, with a little editing for form)
How much gas can I anticipate using when I operate the chamber on a routine basis?
This is a difficult question that does not have an exact answer. The exact answer will depend on how many times you enter the Chamber through the airlock. On an average, suppose you entered the Chamber five times a day and were using "K" size supply tanks (304 cubic feet) for nitrogen gas and "A" size supply tanks (230 cubic feet) for the gas mix. If you have an automatic Airlock, your nitrogen gas will last approximately 47 days and your gas mix will last approximately 72 days. These figures assume you are vacuuming the Airlock to 20 inches (0.69 Kg/sq. cm) of mercury. If you have a manual Airlock, your gas mix will last approximately 25 days, assuming you vacuum the Airlock to 29 inches (1 Kg/sq. cm) of mercury. These figures are calculated for Airlock use only. They do not include gas usage during Chamber purges. Test show in a static environment (no airlock operation/transfer) the chambers will consume .2-.4% hydrogen per day.
How often, at what temperature and for how long do I rejuvenate my catalyst?
Rejuvenating the Catalyst is very important in keeping the Chamber in an anaerobic condition. Rejuvenating the Catalyst a minimum of once a week at 125-200 Celsius for two hours is recommended. Included in the Chamber package are 2 sets of Catalyst Stak-Pak. Replace the Catalyst you rejuvenate with the extra set. Then your Chamber will always have fresh Catalyst. If you have an extremely busy Chamber, you may need to rejuvenate the Catalyst more frequently.
Why does my chamber lose its anaerobic condition over a period of time?
There are a couple of variables that must be considered to answer this question. First, does your Chamber have a leak? (Noted by the Chamber top collapsing over night.) Second, is the catalyst fresh, have they been rejuvenated?Once these variables have been considered and eliminated from the probable cause, concentrate on the hydrogen content in the Chamber. Deficient hydrogen content is usually the cause for losing anaerobic conditions in the Chamber. Oxygen is constantly entering the Chamber by Airlock use and diffusion through the PVC walls. Without the hydrogen the catalyst cannot react to remove the oxygen. If you do not regularly use the Chamber, once a week manually vacuum the Chamber about half way and introduce gas mix (containing hydrogen) into the Chamber. You must keep in mind the dilution factor when the gas mix enters the Chamber. If you are using a 10% hydrogen gas mix your Chamber will not contain 10% hydrogen. It will be diluted to approximately 6% or 7% Hydrogen. (see section 2.0). Coy Labs Oxygen/Hydrogen Analyzer can be used to display the amount of hydrogen in percent that is present in your Chamber. Also, the Analyzer has an alarm that indicates when the hydrogen content goes below 1%. If you have exhausted every probable cause and your Chamber still loses its anaerobic condition, test your gas mix for hydrogen content. We have seen and heard of gas companies that do not comply with customer specifications.
How do I know my catalyst is working and how often should I replace it?
A good test to determine if your catalyst is working is to place a tray containing catalyst inside the Airlock. Place a thermometer in direct contact with the catalyst. Then manually vacuum the Airlock (manual or automatic) to 25" (0.53 Kg/sq. cm) of mercury and back fill it with gas mix containing hydrogen. If the catalyst is working correctly, the temperature will increase due to the reaction of catalyst, oxygen, and hydrogen. Temperature will increase about 10 degrees Celsius over 10 to 15 minutes. Coy recommends catalyst replacement on a yearly basis or if the catalyst does not respond to the above test.
Where do most leaks occur in the anaerobic chamber?
Leaks can occur anywhere in the Chamber but most will be present around work areas. Before you begin leak detection, you must first make sure the Chamber contains your normal amount of pre-mixed gas. A towel saturated with isopropyl alcohol, and allowed to sit in the Chamber for a few minutes, will assist in detecting the very small (slow) leaks. With your gas leak detector, check the following areas first:
  • Gloves and cuffs
  • Along chamber sleeves
  • Under work pad
  • Around airlock seals
  • All corners of the chamber
Share your lab equipment questions and challenges with the laboratory and process equipment specialists at Atlantic Technology Group. The combination of your own experience and knowledge with their product application expertise will create an effective solution.

1 comment :

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