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Previous Product ID 23100-21

Version 01

How to check the O2k-chamber for gas leakage if you do not have time to run an instrumental O2 background test?

Version 02

How to test the airtightness of the O2k-chamber if you do not have time to run an instrumental O2 background test?

  • When a chamber is newly assembled or reassembled due to previous medium leakage, but there is not enough time to start an instrumental O2 background test to check whether the chamber is tight, run the following test overnight:
  1. Add MiR05 to the O2k-chamber and close it by gently pushing the stopper downwards. Siphon off excess medium from the top of the stopper using the ISS. Check that any air bubbles are removed from the chamber.
  2. Decrease the oxygen concentration down to ~ 50 μM (using Dithionite or N2 injection); see: Setting the oxygen concentration.
  3. Let the O2k recording overnight with the chamber closed and illumination switched off.
  4. The oxygen concentration should decrease over time due to the O2 consumed by OroboPOS as it is shown in the figure. In this case, the chamber is assembled properly.
  5. If the oxygen concentration increases over time and/or air bubbles are observed in the chamber, a reassemble of the chamber is needed. For details: MiPNet22.11 O2k-FluoRespirometer manual- 5.2 O2k-chamber assembly

Leaking chamber 2020-02-03 P2-03.png

A story about gas bubbles appearing in the closed chamber

Gnaiger Erich (talk) 16:27, 19 March 2020 (CET)
  • You are an O2k user who assembles the O2k-chamber carefully following the SOP (manual & video). Usually this works very well - but not always ..
  1. You are stressed because you have a persistent problem with a leak after chamber assembly, loosing medium from the chamber (observed by medium dropping out from the OroboPOS holder and connector, or a gas bubble appearing slowly in the closed chamber).
  2. ‘Leaky chamber’, therefore, has to be defined: Here it is not just the oxygen leak (as observed in an instrumental O2-background test), it is actual medium leak – two entirely different processes, although medium leak causes simultaneously an O2 leak, but not the other way around.
  3. You re-assemble again and again, until the chamber appears to be tight. You have no clue, what you did differently. And you are not 100 % sure, if the chamber is now really tight. (This is meant by “When the leakage is so little that cannot be noticed”).
  4. You could test this easily with an instrumental O2-background test - SOP! You can do this even in a short amount of time, if you have other tasks to complete meanwhile. But unfortunately it is already evening, and the lab will be closed. (This is meant by “in a short amount of time”). Well, then you may quickly reduce the oxygen level .. the overnight ‘leaky chamber test’ (we will find a better title).
  5. You may use dithionite quickly. But probably you performed your tests of loosing medium after chamber assembly with H2O, to avoid any sticky medium clogging your sensor connector when medium leaks from the chamber. Do you now titrate dithionite solution into the closed chamber containing H2O? YOU WOULD BE IN TROUBLE! This is well explained in our SOPs, but it is a good idea to clarify, that you should use MiR05 (or a highly concentrated phosphate buffer). (Marco: did you actually use MiR05 – I guess absolutely YES).
  6. You come back to the lab in the morning – BINGO. The chamber is tight. Does this replace the instrumental O2-background test?

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