DETECTION OF C-13 LABELED 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 C-13 for the determination of drug metabolites. After administration of a parent drug labelled with C-13 and extraction of the metabolites from the biological fluids, a C-13 chromatographic profile is determined using the specific detection of the C-13 atomic emission and subtraction of the C-13 natural abundance. Thus, only the compounds which are metabolites with a C-13 enrichment over the natural abundance are detected. [1,3,7 trimethyl-C-13(3)]xanthine which is extensively metabolized by the liver is used as an example.