Headspace analyses of acetone: a rapid method for measuring the 2H-labeling of water

Measurements of a 2H-labeling of water in biological fluids are required for determining the rates of biochemical flux and for estimating body composition. We have been using the method which relies on the base-catalyzed exchange of hydrogen (deuterium) between water and acetone. 2H-labeling of acetone is then determined using GCMS. Although not noted in the original paper, when chloroform is used to extract the acetone there is slow but substantial back exchange between [2H]acetone and solvent (unpublished observations). We report herein on a refinement of the assay that utilizes headspace analysis, which minimizes the number of transfers and decreases sample preparation time and instrument run time.