It occured to me the the selective desorption of oxygen and nitrogen from activated charcoal mentioned here was related to another separation process. In packed column chromatography, substances diffuse through a long molecular sieve jungle at different rates, and are extracted separately from the end of the packed column. The different proportions of gas accumulated from charcoal are very likely due to different diffusion rates of nitrogen and oxygen through the carbon molecular sieve.
So, more effective than this batch process of heating and cooling a vessel might be to pump air through a long packed column. Collect the first gas to come out in one container, and when the slower gas finally reaches the end of the tube, cap the tube and evacuate it into another container. The first gas to come out might actually be quite pure. Charcoal could be effective, but using a precise molecular sieve size might make a big difference.
This isn’t at all as i’ve heard gas chromatography described, but this process works by the same principals.
I wonder if a simple air compressor would be capable of overcoming the pressure drop of a long tube packed with pore spaces of only a few angstroms.