Chromatography Forum

Hello GC enthusiasts,

My goal is to evaluate CO2 concentration in gaseous samples mixed with CO2/Air/Freon.
Expected concentrations will range from 1-20% CO2 v/v.

I'm currently using a GC-MS that is configured with a gas sampling valve, He carrier, LN2 cooling, and a RTX-1 column to identify impurities in Halon 1301 samples.

I also have a TCD and FID available to use.

My initial intuition suggests using the current setup (GC-MS, RTX-1, ~-30C oven temp), and setting the AMU mass range on the MS between 44-145 in order to pick up the CO2 m/z of 44.

It seems that would quantify CO2 (and freon) with this approach, but not the air. Therefore, I would be short of calculating the CO2 concentration.

I'm not sure if that is correct, and if there may be a better option with what I have available.

What would you advise? I am open to purchasing new equipment, if necessary (budget <$10K).

If you have a TCD available, you would be advised to use that for the CO2. GC/MS for the fixed gases can be challenging and TCD with helium carrier would be simple pursuit. Column like a Q polymer should work well.

Other option is FID with a methanizer but at those high levels a TCD would be the first choice.

Clarify, as well, you want to do the air as well? In the Halon 1301?

Best regards,

We used packed-column GC with TCD decades ago to determine CO2 levels in sealed food pouches. It was straightforward.

There might also be specialized equipment for CO2 these days.

For CO2 on MS you would need to begin the scan range at least at 43m/z, since the exact mass can drift between scans a little and if you run it at exactly the mass you need it can drift in and out and you will have clipping of the signal sporadically.