Number: 2005-022-1-200
Title: Calibration of organic and
inorganic oxygen-bearing isotopic reference materials
Task Group
Chairmen: Tyler
B. Coplen and Willi
A. Brand
Members: John
Karl Böhlke, Matthias
Gehre, Manfred
Groening, Harro
A.J. Meijer, Hilary
Stuart-Williams, Gregory C. Turk, and Roland
A. Werner
Objective:
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.
Description:
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.