Determination of δ17O values of reference water samples VSMOW and SLAP

δ17O and δ18O values have been measured for isotopic reference samples VSMOW and SLAP, the intercomparison material GISP and one laboratory standard sample MSA6. The oxygen liberated by the decomposition of these water samples with bromine pentafluoride is analyzed directly by the mass spectrometer. The δ17OVSMOW values of SLAP, GISP and MSA6 are determined as −28.58, −12.59 and −4.18‰, respectively. The normalized δ17O values on the VSMOW-SLAP scale for GISP and MSA6 are −12.71 and −4.22‰, respectively, taking δ18OSLAP = − 55.5‰ and a slope of 0.52 for the three-isotope plot of oxygen. The credibility of the method is shown by analyzing NBS-28, a silicate reference sample, and the values obtained for δ18O and δ18O are 4.86 ± 0.03 (1 σ) and 9.31 ± 0.03 (1 σ), respectively.