A method for oxygen isotope analysis of milligram quantities of water and some of its applications

A method has been developed by which bromine pentafluoride and small amounts of water are reacted in a nickel vessel at 80°C to liberate oxygen in 100% yield. The oxygen is converted to CO₂, which is analyzed on an isotope ratio mass spectrometer. The oxidation reaction takes place instantaneously, and the conversion of the liberated O to CO₂ requires approximately 15 minutes. There are no measurable memory effects in the method and the reproducibility is ±0.1‰. A value of 1.0407 was determined for the CO₂-H₂O fractionation factor at 25°C, a number necessary for relating standards in use by various workers. This value is in exact agreement with that obtained by Compston and Epstein in the same laboratory using a reduction technique but is in serious disagreement with values determined by other workers. An application of this technique has been made to the study of a meteorological problem.