Analysis of 18O enrichment in biological fluids by continuous flow-isotope ratio mass spectrometry

A novel method is described for the analysis of 18O in urine by continuous flow-isotope ratio mass spectrometry (CF-IRMS), after sample equilibration with CO2. The method is shown to be fast, precise and accurate and therefore facilitates studies of total body water and water turnover in the clinical field. The method uses existing CF-IRMS instrumentation with minor hardware modification which does not compromise routine analysis of 13C and 15N. This method emphasizes the versatility of CF-IRMS and thus its economy for the biomedical research group using stable isotope tracers.