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- Joined: Sun Feb 17, 2019 9:59 pm
Any geochemists here, particularly organic geochemists?
I'm currently having issues making an unequivocal identification of a troublesome hydrocarbon biomarker, namely gammacerane, using single quad GCMS. Using MSMS also will not work as many similar biomarkers have the same parent and daughter ions.
Gammacerane: due to it's molecular symmetry it is well known that it gives a relatively simple mass spec with a very dominant base ion of 191 mz.
However it also elutes in an area of the chromatogram filled with other biomarkers, mainly all sorts of hopanes.
The reference oil we use shows a tiny abundance of gammacerane, along with a mass spec that does NOT show a dominant 191 mz peak. I suspect, but can't be sure, this gammacerane peak has been mis-identified in our reference sample.
In my samples, (which admittedly give very messy spectra),the tentatively identified gammacerane also shows a mass spec with a non-dominant 191 mz peak, often with a sizeable 205 mz peak (usually a methylhopane peak).
Can anyone with much greater knowledge of this biomarker than I suggest whether co-elution would have the effect of making the 191 mz peak appear less dominant? Or could it be more likely that the gammacerane HAS been mis-ID'd? Difficult to answer when I haven't provided a chromatogram, I know, but do your best if you can. I'd be very grateful for any guidance on this, it's driving me round the twist. It is out of the question to buy a synthetic gammacerane standard, sadly (Phd student, no money).