How do you test hydrogen retention in a Hungate tube?

I am working in lab to test for hydrogen production of purple non-sulfur bacteria under different conditions, but prior to doing so am testing how well the Hungate tubes used for growth can contain the gas produced. To do so we flushed out the air inside with 1000 ppm hydrogen by piercing the septum with a vent... show more I am working in lab to test for hydrogen production of purple non-sulfur bacteria under different conditions, but prior to doing so am testing how well the Hungate tubes used for growth can contain the gas produced. To do so we flushed out the air inside with 1000 ppm hydrogen by piercing the septum with a vent needle and another needle feeding hydrogen in. What method should be used to run a GC-TCD test to determine its retention? Thanks!
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