Premium
Accuracy of δ 18 O isotope ratio measurements on the same sample by continuous‐flow isotope‐ratio mass spectrometry
Author(s) -
Wong William W.,
Clarke Lucinda L.
Publication year - 2015
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7390
Subject(s) - isotope ratio mass spectrometry , chemistry , isotope , analytical chemistry (journal) , mass spectrometry , stable isotope ratio , sample (material) , detection limit , continuous flow , sample preparation , chromatography , nuclear physics , physics , mechanics
Rationale The doubly labeled water method is considered the reference method to measure energy expenditure. Conventional mass spectrometry requires a separate aliquot of the same sample to be prepared and analyzed separately. With continuous‐flow isotope‐ratio mass spectrometry, the same sample could be analyzed sequentially for both 2 H and 18 O content and thus minimize sample requirement, reduce analytical cost, and avoid memory effect. Methods The 2 H contents of 197 urine samples collected from 22 doubly labeled water studies were determined using a Thermo Delta V Advantage continuous‐flow isotope‐ratio mass spectrometer. The 18 O content of these samples was measured either using a separate aliquot of the same sample using a VG Isogas gas‐isotope‐ratio mass spectrometer or using the same sample following the 2 H measurements on a Thermo Delta V continuous‐flow isotope‐ratio instrument. Results The δ 18 O values using the same aliquot of samples were accurate to 0.18 ± 2.61 ‰ (mean difference ± standard deviation (SD); 95% CI, –0.18 to 0.55 ‰; P = 0.33) compared with the values based on the standard conventional method. Bland and Altman pair‐wise comparison also yielded a bias of 0.18 ‰ with a 95% limit of agreement between –4.94 and 5.30 ‰. Conclusions The study demonstrated that continuous‐flow isotope‐ratio mass spectrometry is capable of producing accurate 18 O measurements on the same sample after 2 H measurements. The method greatly reduces the analytical cost and sample size requirement and could easily be adopted by any laboratories equipped with a continuous‐flow isotope‐ratio mass spectrometer. Copyright © 2015 John Wiley & Sons, Ltd.