Oxygen isotopic analysis of silver orthophosphate using a reaction with bromine

A simple and precise method of determining the oxygen isotopic composition of Ag3PO4 has been developed in which orthophosphate is condensed to pyrophosphate and higher polymeric forms at elevated temperatures using Br2 as a reactant in a heated quartz vessel, releasing about 17.5% of the oxygen present as O2 gas. The O2 is converted to CO2 using a heated carbon rod and analyzed using a mass spectrometer. The precision of the δ 18O determination is better than 0.07‰ when reaction furnace temperature is regulated to within ±0.5°C. This method offers advantages of speed, safety, and cost over conventional BrF5 decomposition of silver phosphate.