Carbon radioactive isotope dating
In Liquid Scintillation Counting, for example, incomplete synthesis of acetylene during lithium carbide preparation may result in a low yield and concurrent fractionation.
The activity of this hypothetical level of C14 activity is equal to the activity of the absolute international radiocarbon standard.
If it is the AMS δ13C, it cannot be used for dietary or metabolic pathway studies.
Reported δ13C values from Beta are always the values measured in the IRMS.
In the case of shellfish, for example, marine shells typically possess a δ13C value between -1 and 4 o/oo (per mille), whereas river shells possess a value of between -8 and -12 o/oo (per mille).
Thus, in a case where the precise environment of the shell is not known, it is possible to determine the most likely environment by analysis of the δ13C result.