Most applications are based on the use of 13C as the labeling and the measurement of 13C-12C ratios with an isotope ratio mass spectrometer ( IRMS ) ; an MS with a detector designed to measure a few select ions and return values as ratios .
Most applications are based on the use of 13C as the labeling and the measurement of 13C-12C ratios with an isotope ratio mass spectrometer ( IRMS ) . A IRMS is an mass spectrometer with a detector designed to measure a few select ions and return values as ratios .