A new high-quality set of singly (2H) and doubly (2H and 18O) stable isotope labeled reference waters for biomedical and other isotope-labeled research

Abstract

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 2H water and highly 18O-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 2H, and another set of Doubly Labeled Waters, enriched in both 2H and 18O. They cover δ2H and δ18O 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.