Pyrolysis against hydra and laser techniques for measuring the isotopic enrichment of deuterium- and oxygen-18-labeled water

Abstract

The deuterium- and oxygen-18-doubly labeled water technique, is the gold standard for determiningtotal energy expenditure (TEE). The progress of researches with this technique happened in parallel with many other analytical techniques using isotopes in aqueous samples. A new analytical method is being implemented at the Stable Isotope Center (SIC) of the Institute of Biosciences ofBotucatu/SP (IBB) - UNESP, which requires consolidation of the sample preparation and analysis methods in order to obtain accurate and precise data in biomedical studies. Hence, this project aims to compare three preparation and measuring techniques of relative isotopic enrichment of oxygen-18 (´18O) and deuterium (´2H) in natural and slightly enriched samples. For this purpose, thermal decomposition ("pyrolysis") will be used and the methods to prepare and analyze the samples of natural waters and waters slightly enriched with ´2H and ´18O available in other institutions will be assessed, together with the memory effect of enriched water on the results of enriched water from the natural abundance. A total of 60 natural water samples and 60 isotopically enriched water samples will be analyzed by three different analysis techniques: the "hydra" technique, used in the Mass Spectrometry Laboratory of the School of Medicine of Ribeirão Preto/SP, USP, the "laser" technique used in the Center of Nuclear Energy in Agriculture of USP in Piracicaba, and the "pyrolysis" technique used in the SIC-IBB - UNESP. The fulfillment of these objectives should result in common ´2H and ´18O values from the three research centers, with good correlation between the values and small memory effect on the SIC-IBB laboratory equipment. Thus, accurate and precise information will be obtained which will allow the application of the SIC-IBB method in future biomedical researches. (AU)