title: The use of infrared spectrophotometry for measuring body water spaces.
abstract: BACKGROUND
  The conventional method of measuring total body water by the deuterium isotope dilution method uses gas isotope ratio mass spectrometry (IRMS), which is both expensive and time-consuming. We investigated an alternative method, using Fourier transform infrared spectrophotometry (FTIR), which uses less expensive instrumentation and requires little sample preparation.
  
  
  METHODS
  Total body water measurements in human subjects were made by obtaining plasma, saliva, and urine samples before and after oral dosing with 1.5 mol of deuterium oxide. The enrichments of the body fluids were determined from the FTIR spectra in the range 1800-2800 cm-1, using a novel algorithm for estimation of instrumental response, and by IRMS for comparison.
  
  
  RESULTS
  The CV (n = 5) for repeat determinations of deuterium oxide in biological fluids and calibrator solutions (400-1000 micromol/mol) was found to be in the range 0.1-0.9%. The use of the novel algorithm instead of the integration routines supplied with the instrument gave at least a threefold increase in precision, and there was no significant difference between the results obtained with FTIR and those obtained with IRMS.
  
  
  CONCLUSIONS
  This improved infrared method for measuring deuterium enrichment in plasma and saliva requires no sample preparation, is rapid, and has potential value to the clinician.
authors.affiliation: MRC Dunn Clinical Nutrition Centre, Hills Road, Cambridge CB2 2DH, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Jennings
authors.forename: L
authors.initials: L
authors.lastname: Bluck
authors.forename: A
authors.initials: A
authors.lastname: Wright
authors.forename: M
authors.initials: M
authors.lastname: Elia
mesh_terms: D001834:Body Water / Q000737:chemistry*; D017666:Deuterium Oxide / Q000032:analysis / Q000097:blood / Q000652:urine; D006801:Humans; D013058:Mass Spectrometry; D011865:Radioisotope Dilution Technique; D012463:Saliva / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D017666:Deuterium Oxide