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negative peak in fid before methane
Posted: Wed Jan 04, 2012 4:03 am
by mallikka
i am using an agilent gas chromatograph with tcd and fid.i am using helium as an carrier gas for the fid.i inject my gas directly in the fid and i am getting a negative peak before methane.this peak is not observed in the standard gas.even when i use a nucon gc, with nitrogen as the carrier i am facing the same problem.please help.thanks
Re: negative peak in fid before methane
Posted: Wed Jan 04, 2012 6:38 am
by chromatographer1
what is different from your sample gas from your std gas?
Rod
Re: negative peak in fid before methane
Posted: Wed Jan 04, 2012 7:03 am
by mallikka
hi! my sample gas is the gas desorbed from subsurface soil samples using orthophosphoric acid.my standard gas does not have co2 in it.i injected another standard gas having co2 and i got the same signature as my sample.there was a dip before methane.i am using agilent 7890a with helium as the carrier in fid