Isotope ratio mass spectrometry in antidoping analysis: The use of endogenous reference compounds.

For the selected ERCs of non-sporting volunteers and the urinary specimens from more than 1000 sportsmen, we can propose a maximum SD of 0.54‰ and range of 1.2‰ for delta 13 C values as acceptance criteria to detect potential outliers. These cases can be caused by the external masking effect of the administration of a substance modifying the delta values or outliers due to unforeseen procedural artifacts.