Calibration of δ ¹⁷ O and δ ¹⁸ O of international measurement standards – VSMOW, VSMOW2, SLAP, and SLAP2

Due to exhaustion of the two primary calibration materials, Vienna Standard Mean Ocean Water (VSMOW) and Standard Light Antarctic Precipitation (SLAP), two replacement materials, VSMOW2 and SLAP2, were created with isotopic compositions as close as possible to the original standards in their D/H and (18)O/(16)O ratios. Measurements of the delta(17)O composition constitute therefore an appropriate independent check of the achieved isotopic adjustment. Aliquots from ampoules of VSMOW, VSMOW2, SLAP, and SLAP2 were fluorinated by BrF(5) and analyzed using a dual-inlet Delta E mass spectrometer. VSMOW2 and SLAP2 were found to be indistinguishable from VSMOW and SLAP, respectively, in their delta(17)O and delta(18)O values within measurement uncertainties. This result is a confirmation of the successful isotopic matching of VSMOW2 and SLAP2 to their predecessors. Further checks of the delta(17)O value of SLAP2 seem desirable.