Dear Matheus,

First, I take it you want to measure on CO2 gas? Then the thing is quite simple: the 18O abundance is about 0.2% (ending up as 0.4% on mass 46), and any 14C has to compete with that. So, let's say, as soon as you have about 0.01% of all your C's as 14C, you can identify it using IRMS (provided you know the 18O isotope abundance of the specific CO2 quite well). Then, however, your CO2 will be highly radio-active, as this is about 10^8 times the normal 14C abundance. I personally don't think you would want to do that, since there are far easier techniques to detect the radioactivity of 14C at that level or even considerably below it.

Hope this helps.

kind regards,

Harro Meijer

Op 22 okt. 2014, om 07:50 heeft Matheus Carvalho het volgende geschreven:

Dear all, suppose there is a material composed by a mixture of 14C, 13C and 12C, with the 14C content artificially high. Would it be possible to estimate the quantities of the 3 isotopes based on 46/44 mass? Suppose there are standards with 14C known quantities to help with this.
Any comment is appreciated. Thank you,

--
Matheus C. Carvalho
Senior Research Associate
Centre for Coastal Biogeochemistry Research
Southern Cross University
Lismore, NSW, Australia
61-4-8899-0092

Prof.dr. Harro A.J. Meijer
Centrum voor IsotopenOnderzoek (CIO)
Energy and Sustainability Research Institute Groningen (ESRIG)
Rijksuniversiteit Groningen
Nijenborgh 4, 9747 AG  Groningen, Netherlands
tel +31-50-3634760 
http://www.rug.nl/fmns-research/cio/index