Detection of 13C labelled compounds by gas chromatography coupled to atomic emission detection — Application to caffeine metabolites

This paper illustrates the use of gas chromatography coupled to atomic emission detection (GC-AED) and of the stable isotope tracer 13C for the determination of drug metabolites. After administration of a parent drug labelled with 13C and extraction of the metabolites from the biological fluids, a 13C chromatographic profile is determined using the specific detection of the 13C atomic emission and subtraction of the 13C natural abundance. Thus, only the compounds which are metabolites with a 13C enrichment over the natural abundance are detected. [1,3,7 trimethyl-13C3]xanthine which is extensively metabolized by the liver is used as an example.