Isotopic Fractionation of NBS Oxalic 14C Standard and Its Effect on Calculated Age of Materials

Abstract

There is much controversy about the significance to radiocarbon dating of isotopic fractionation during the oxidation to CO2 of NBS oxalic acid, the carbon-14 dating standard. To check the effect of fractionation, 30 routine potassium permanganate oxidations of oxalic acid were performed. The isotopic composition of resulting CO2 was determined mass-spectrometrically. delta-13C results ranged between -17.7 and -21.2, with an average of -18.9 per mil wrt PDB. The effect of not applying an isotopic fractionation correction to NBS oxalic acid when performing age calculations is evaluated.