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Mass spectrometric analysis of stable-isotope-labelled amino acid tracers

A group of continuous-flow isotope-ratio mass spectrometry (CF-IRMS) techniques that have been introduced recently, promise to improve greatly the analysis of stable isotope tracers in many areas of life science, including human nutrition. These offer the ability to process rapidly large numbers of samples. This is fundamental, especially if techniques developed for clinical research are to be used for diagnosis. The present paper charts the development of CF-IRMS techniques, including GC-combustion isotope-ratio mass spectrometry (GC-C-IRMS; also termed compound-specific isotope analysis) and contrasts this with GC-mass spectrometry (GC-MS), demonstrated by studies of protein metabolism using stable-isotope-labelled amino acid tracers.