18 O/ 16 O ratio measurements of inorganic and organic materials by elemental analysis–pyrolysis–isotope ratio mass spectrometry continuous‐flow techniques

We have used a high‐precision, easy, low‐cost and rapid method of oxygen isotope analysis applied to various O‐bearing matrices, organic and inorganic (sulfates, nitrates and phosphates), whose 18 O/ 16 O ratios had already been measured. It was first successfully applied to 18 O analyses of natural and synthetic phosphate samples. The technique uses high‐temperature elemental analysis–pyrolysis (EA‐pyrolysis) interfaced in continuous‐flow mode to an isotope ratio mass spectrometry (IRMS) system. Using the same pyrolysis method we have been able to generate a single calibration curve for all those samples showing pyrolysis efficiencies independent of the type of matrix pyrolysed. We have also investigated this matrix‐dependent pyrolysis issue using a newly developed pyrolysis technique involving 'purge‐and‐trap' chromatography. As previously stated, silver phosphate being a very stable material, weakly hygroscopic and easily synthesized with predictable 18 O/ 16 O values, could be considered as a good candidate to become a reference material for the determination of 18 O/ 16 O ratios by EA‐pyrolysis‐IRMS. Copyright © 2011 John Wiley & Sons, Ltd.