Determination of δ17O values of reference water samples VSMOW and SLAP

delta(17)O and delta(18)O 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 delta(17)O(VSMOW) values of SLAP, GISP and MSA6 are determined as -28.58, -12.59 and -4.18 parts per thousand, respectively. The normalized delta(17)O values on the VSMOW-SLAP scale for GISP and MSA6 are -12.71 and -4.22 parts per thousand, respectively, taking delta(18)O/(SLAP) = -55.5 parts per thousand 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 delta(17)O and delta(18)O are 4.86 +/- 0.03 (1 sigma) and 9.31 +/- 0.03 (1 sigma), respectively. (C) 1997 Elsevier Science B.V.