Stable oxygen isotope compositions (δ18O values) of two commercial and one synthesized silver orthophosphate reagents have been determined on the VSMOW scale. The analyses were carried out in three different laboratories: lab (1) applying off-line oxygen extraction in the form of CO2 which was analyzed on a dual inlet and triple collector isotope ratio mass spectrometer, while labs (2) and (3) employed an isotope ratio mass spectrometer coupled to a high-temperature conversion/elemental analyzer (TC/EA) where Ag3PO4 samples were analyzed as CO in continuous flow mode.
The δ18O values for the proposed new comparison materials were linked to the generally accepted δ18O values for Vennemann's TU-1 and TU-2 standards as well as for Ag3PO4 extracted from NBS120c. The weighted average δ18OVSMOW values for the new comparison materials UMCS-1, UMCS-2 and AGPO-SCRI were determined to be + 32.60 (± 0.12), + 19.40 (± 0.12) and + 14.58 (± 0.13)‰, respectively. Copyright © 2011 John Wiley & Sons, Ltd.