Dear Esteban

It's certainly a little overkill to use ICPMS for oxygen. It will be rather difficult to measure it by feeding it to the ICP directly.

The only way I could think of is to feed the gas into the reaction cell and measure oxo-ions of La+ for example. Their abundance will be correlated with the amount of oxygen in the gas. It's however going to be difficult to establish a calibration to accurately determine the concentration of O2 and there will certainly be interference from water vapor in the gas.

Dear Esteban

I would suggest a Clark sensor.

Best

Gunnar

You will find a cheap device (