IUPAC

The purpose of this project is to assess the relative amounts of oxygen isotopes in internationally distributed organic and inorganic isotopic reference materials and publish "consensus" values and uncertainties for these materials.

During the past three decades, the determination of the relative amounts of stable isotopes of the light elements (H, C, N, O, and S) has dramatically increased because of expanded use in hydrology, environmental studies, microbiology, forensic investigations, atmospheric investigations, oceanography, etc. In the last 10 years, determination of the relative amounts of the isotopes of oxygen in organic and inorganic solids has increased because of developments in instrumentation. In the last 5 years, several new oxygen isotopic reference materials have been prepared. However, the values of the relative amounts of oxygen isotopes in these new materials and in older materials are not well known. Thus, the problem arises that two isotope laboratories analyzing the same sample may not report the same result within analytical uncertainty because they do not know what values to accept for internationally distributed oxygen isotopic reference materials.

The purpose of this work is to bring together expert analytical laboratories (Jena, Reston, Leipzig, Canberra, and Zurich) to measure the relative amounts of oxygen isotopes in isotopic reference materials. This highly coordinated analytical effort will include inorganic materials, organic materials, atmospheric oxygen, and two water reference materials-the scale for expressing relative amounts of oxygen isotopes in natural materials is anchored by the two isotopic reference materials VSMOW water and SLAP water. Strict analytical protocols will be designed and followed by all laboratories. An initial phase of the project will be to assess oxygen exchangeability of potential materials to eliminate those with exchangeable oxygen. At the conclusion of the analytical effort, task group members will convene for a 3-day workshop to determine "best" values and uncertainties. Some of the materials under consideration for inclusion in this proposed project are IAEA-CH-3 cellulose, IAEA-CH-6 sucrose, IAEA-600 caffeine, IAEA-601 & IAEA-602 benzoic acid, USGS40 & USGS41 L-glutamic acids, USGS32 KNO3, IAEA-NO-3 KNO3, USGS34 KNO3, USGS35 NaNO3, NBS-127 BaSO4, and IAEA-SO-5 & IAEA-SO-6 BaSO4.

March 2007 - Since this project commenced, thousands of very difficult measurements have been performed in this coordinated analytical measurement program. A meeting in Europe is planned for May 2007 to bring together task group members to determine consensus values for internationally distributed oxygen isotopic reference materials analyzed in this program.

 <project announcement published in Chem. Int. Mar-Apr 2006, p. 29>