methane measurment using GC-MS

[tjpark]

Hello...
i am a beginner in this area and trying to do biogas analysis using GC-MS, but it is not common GC-MS used for biogas analysis.

i would like to ask that GC-MS can be more easier for the biogas analysis compared to GC-FID for beginner ?

thanks

TJ

[James_Ball]

You would have problems if doing trace analysis for methane since any trace oxygen would give you the same m/z of 16 as the methane. Though for methane the M-1 would be 15, but you are still down in the low mass region where it is going to be difficult to deal with interferences. If you are looking at ppm levels then it should not be so much of a problem.

[rb6banjo]

It doesn't get much easier than FID as a detector for gas chromatography. The FID is also exceptionally sensitive. If you mount a rotary injection valve in the oven of your GC, you can make fixed-volume injections onto your column. Most everything will elute after methane on a DB-1 (Agilent Technologies) or Rtx-1 (Restek), or SPB-1 (Supelco) phase. I analyze CO2 for methane like this using the Rtx-1 phase and a FID.

How do you collect a sample of your biogas for your analysis?

[mikeyswood]

I do something similar with methyl fluoride. I'm using a PlotQ column to separate the gasses (Air, CO2, MeF) and TCD/MSD for my analysis. The PlotQ gives me good separation between the gasses so you should be able to see the difference between O2 and Me. I'm now trying a molesieve column to separate N2 from O2. I should know results in a few days...