Chromatography Forum

Hi everyone,

I am an undergrad at the University of California San Diego and am working for one of my professors. I have been tasked with helping someone from another lab which involves looking for hydrogen gas and its isotopes on a GC-MS. To my understanding this is not possible, however, I am giving it the old college try.

I have been adjusting the scan parameters in hopes of finding something, but all attempts so far have been unsuccessful. I am reaching out to the community here seeking any advice which may help.

I have adjusted the mass range the instrument looks for to 1.6-14. The H2 elutes at 1.5 min at a 1mL/min He gas flow rate. This is evidenced by a negative peak in the chromatogram, which is nothing more than noise. I interpret this as just an interruption of He gas flow at the detector by the 1 mL volume of H2 passing through.

Any advice will be greatly appreciated!

What model mass spec are you using?

I know some models don't scan below 10m/z so you may not be seeing and actual scan of mass 1-9.

What an interesting concept! Vacancy chromatography using a MS as the detector! Well done.

If this is the case, then you should see a significant increase in sensitivity by running nitrogen as your carrier gas.

Thank you both for the replies.

I am working with an Agilent 7820A GC System with an Agilent 5975 MS.

There has been some success since my initial post. By reducing the scan parameters to scan in the 1.6 - 4.0 m/z range, I am able to detect the UHP H2 gas injections as well as the H2 in my samples. The chromatogram appears as positive peaks now without the noise from He.

I did not think about using Nitrogen as the carrier gas. Thank you mckrause. This will be especially helpful as next I am going to try D2 (and possibly H-D) which has not show up with the current H2 method due to the He.