Determination of deuterium level in biological fluids by isotope ratio mass spectrometry.

Water is produced by vacuum sublimation of biological fluids directly into reaction vessels in preparation for reduction using zinc. Following heating to 450 degrees C the hydrogen produced is admitted directly to the mass spectrometer. The standard derivation, sigma 10 of analysis of water samples was 1.08-1.23% while for blood plasma sigma 6 = 2.02-2.62%. The method allows the determination of very low levels of deuterium in biological fluids, thus allowing very small doses of deuterium oxide to be used in studies of body water in animals and possibly humans.