Reference Materials

Solid Reference Materials - Caffeine, Glutamic acids, Benzoic acids ... - BGC-IsoLab has engaged generating new international Reference Materials. From a company in Bremen we acquired a large amount of natural caffeine from the decaffeination process. The material was rigorously tested for homogeneity and forwarded to the IAEA in Vienna. The work was conducted under a contract with the IAEA (302-F3-GFR-12020 / B5- GFR-30590). The advantage of caffeine is that it contains both nitrogen and carbon in comparable quantities within the same molecule. Moreover, it has non-exchangeable oxygen that makes the material suited for HTC techniques. Calibration of the material is on the way (with support from IAEA and IUPAC). The material is available as IAEA 600.

A similar effort in collaboration with the USGS in Reston (VA) has been completed. The USGS prepared two isotopically different samples of glutamic acid for high precision determination of δ¹³C and δ¹⁵N. One of the acids was slightly enriched in δ¹³C and δ¹⁵N within the realm of naturally occurring isotope values.

With A. Schimmelmann (Univ. Indiana, Bloomington) we engaged in generating a new (organic) δ¹⁸O reference material for on-line oxygen isotope analyis. We purchased a larger amount of high purity benzoic acid from Merck and exchanged the oxygen with ¹⁸O enriched water (pH 0, 90°C, 3 weeks reaction under reflux conditions) for 1/3rd of the material. The exchange reaction was made in collaboration with the inorganic chemistry institute of the University of Jena (M. Doerr and W. Weigand). The two materials were then isotopically measured using a high temperature pyrolysis technique (Jena Isolab) and a medium temperature off line decarboxylation reaction (Indiana). Both experiments resulted in similar values for the two materials, one at about +23 per mill and the enriched form at about +71 per mill vs. VSMOW. The material was forwarded to the IAEA in Vienna for further handling. The work done in Bloomington was sponsored by the IAEA. The materials are now available as IAEA 601 and IAEA 602.

Results have been published:

H. P. Qi, T. B. Coplen, H. Geilmann, W. A. Brand, and J. K. Böhlke, "Two new organic reference materials for δ¹³C and δ¹⁵N measurements and a new value for the δ¹³C of NBS 22 oil," Rapid Communications in Mass Spectrometry 17 (22), 2483-2487 (2003).

MPG.PuRe

T. B. Coplen, W. A. Brand, M. Gehre, M. Gröning, H. A. J. Meijer, B. Toman, and R. M. Verkouteren, "New guidelines for δ¹³C measurements," Analytical Chemistry 78 (7), 2439-2441 (2006).

MPG.PuRe