With the presented building blocks, we show how to assure a reliable and accurate isotope analysis for the DLW method, both for human and for animal applications. Although our measurements have been performed using isotope ratio mass spectrometry, most of the procedures are also useful for laser spectrometry.

The Centre for Isotope Research (CIO) at the University of Groningen has operated a radiocarbon (14C) dating laboratory for almost 70 years. In 2017, the CIO received a major upgrade, which involved the relocation of the laboratory to new purpose-built premises, and the installation of a MICADAS accelerator mass spectrometer. This period of transition provides an opportunity to update the laboratory’s routine procedures. This article addresses all of the processes and quality checks the CIO has in place for registering, tracking and pretreating samples for radiocarbon dating. Complementary updates relating to radioisotope measurement and uncertainty propagation will be provided in other forthcoming publications. Here, the intention is to relay all the practical information regarding the chemical preparation of samples, and to provide a concise explanation as to why each step is deemed necessary.

RATIONALE:Research using water with enriched levels of the rare stable isotopes of hydrogen and/or oxygen requires well-characterized enriched reference waters. The International Atomic Energy Agency (IAEA) did have such reference waters available, but these are now exhausted. New reference waters thus had to be produced in sufficient quantity, and higher characterization quality was desired. METHODS: The reference waters have been prepared gravimetrically from three parent waters: natural water, pure 2 H water and highly 18 O-enriched water. These parent waters have been thoroughly assessed for their full isotopic compositions. To ensure the integrity and correctness of the gravimetric procedure, validation measurements have been carried out on the isotopic composition of the produced reference waters by two of our laboratories. These measurements corroborate the values obtained on the basis of gravimetric data. RESULTS: Two new sets of three reference waters enriched in the stable isotopes have been produced and certified: one set of singly labeled waters, only enriched in 2 H, and another set of Doubly Labeled Waters, enriched in both 2 H and 18 O. They cover δ 2 H and δ 18 O values in the range of 800-16000 ‰ and 100-2000 ‰, respectively. The process has led to highly accurate isotopic values for these waters. CONCLUSIONS: These reference waters are now available (called IAEA-604 to IAEA-609). They will be valuable as reference materials for all fields using isotope labeling of water, most prominently, but not exclusively, biomedical research (body composition analyses, metabolic rate measurements). The two waters with the lowest enrichments will also be useful as anchor values for isotope measurements around the natural range. © 2015 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.Analysis of the stable isotope ratios of hydrogen and oxygen has widespread applications in a variety of sciences, such as atmospheric research, [1,2] hydrology, [3,4] (paleo) climatology, [5][6][7][8] and medicine and biology. An example of the latter is the application of stable isotopes in water as tracers to assess the water fraction of the total body mass, [9][10][11] and the energy expenditure of humans and animals. [12][13][14] Both methods have a non-destructive, nonrestrictive character: a small portion of water labeled with one or both stable isotopes must be administered to the person or the animal, and one (singly labeled) or two (doubly labeled) samples of one of the possible body fluids (saliva, blood, urine) must be taken. The way in which the singly labeled method establishes the total amount of body water (and thus produces valuable information about body composition) is straightforward: it is based on the dilution of the original administered isotope label by the total body water. Provided that the administered amount and the enrichments of the labeled water are well known, the labeled water has been fully equilibrated through the body, and the final isotope measurement i...

The DLW method in humans can be reliably applied using saliva as sampling fluid. TEI-TEE as well as AEE contributes significantly to changes in fat mass over an 8-day period.

Natural abundance carbon 13 magnetic resonance spectroscopy (I3C MRS) allows the proportion of saturated and unsaturated fatty acids in adipose tissue to be measured repeatedly and non-invasively. Eleven infants and two of their mothers underwent "C MRS.