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Cavity ring‐down spectrometer for total energy expenditure using doubly‐labeled water
Author(s) -
Richman Bruce A.,
Schoeller Dale A.,
Thorsen Tom,
Shriver Tim,
Crosson Eric R.
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.220.1
Subject(s) - doubly labeled water , chemistry , analytical chemistry (journal) , isotope , body water , zoology , environmental chemistry , body weight , physics , medicine , biochemistry , quantum mechanics , basal metabolic rate , biology
Understanding obesity and weight control, a health problem of epidemic proportions, includes increased use of total energy expenditure (TEE) measurements using the doubly labeled water method (DLW). Unfortunately, until now, the DLW method required expensive and operationally complex isotope ratio mass spectrometry (IRMS), which has restricted the widespread use of the DLW method. To address this limitation, we developed a commercial DLW analyzer based on wavelength‐scanned cavity ring‐down spectroscopy (WS‐CRDS). This table‐top analyzer measures both isotopic ratios of water directly (δ 18 O/ 16 O and δD/H). Advantages of WS‐CRDS include less user training, no chemical conversion of the water specimen, no high vacuum system, a smaller footprint, and less capital investment. We compared measurements of water and 14 sets of urine samples using both WS‐CRDS and IRMS. The within‐day precision for natural abundance and enriched water standards were 0.26‰ and 0.04‰ for δD/H and δ 18 O/ 16 O for_the WS‐CRDS; compared to 0.92‰ and 0.05‰ for IRMS. The mean within‐subject difference (±SD) between instruments for total body water was 0.2±0.4 kg (CV=0.5%) and that for TEE was 22±158 kcal/d (CV=5%). The major limitation of WS‐CRDS was a memory between successive specimens for deuterium of 6%, requiring that each specimen be injected at least five times in succession. This work was supported by NIH grant R44 RR021297.