Comparison of stable isotope reference samples

Use of light stable isotope ratio measurements has proliferated in the past decade. The need for procuring additional stable isotope reference materials was recognized at an International Atomic Energy Agency (IAEA) consultants' meeting convened in 1976¹. This group recommended acquisition of two carbonates, two carbon dioxide samples, a biotite, a sulphate, and other reference materials. We report here on the mass-spectrometric analysis of these and other reference samples in a single laboratory to minimize interlaboratory calibration errors. A result of this work is an improved equation for relating the PDB isotope scale (belemnite from the Peedee Formation of South Carolina adopted in the 1950s as a reference in palaeotemperature studies²) to the V-SMOW (Vienna-Standard Mean Ocean Water) scale¹.