OK boiling will drive off gases that start dissipating in the minute the heat is turned off.
Like for instance one idea to keep oxygen off is using a common siphon (remember them?) fill it with CO2 gas DRY, and use thw valve to fill the bottle(s) with heavier than air CO2 gas, thereby keeping oxygen out of the bottle.
BUT! CO2 absorbs fairly quickly into solution and will alter pH in solutions that are close to neutral..... so its give and take.
My question is : what was just 12 ml of TEA supposed to do in a massive solution with 4 liter of water (4000 ml) that sucks up all oxigen it comes in contact with?