Headspace analyses of ²H labeling of acetone: enabling studies of fatty acid oxidation in vivo.

We demonstrate that one can measure low levels of ²H labeling (e.g., <0.025% excess ²H) by exchanging hydrogen (deuterium) in water with acetone and subjecting samples to gas chromatography-pyrolysis-isotope ratio mass spectrometry. This analytical method circumvents the need to use typical off-line reduction methods that convert water to hydrogen gas prior to isotope ratio mass spectrometry or the need to purchase extra peripheral devices that would permit the direct analysis of water labeling. This method enables routine measurements of fatty acid oxidation in rodents; that is, one administers a ²H-labeled fatty acid(s) and then quantifies the production of ²H-labeled water.