Marilyn Fogel wrote:

> I may be missing something, but I am having trouble finding and 
> purchasing isotope standard materials, particularly for carbonates.

NBS 19, LSVEC (recommended for 13C[1]) and others are available from 
IAEA AQCS Division [2].

For internal lab use we tried to prepare one standard by ourself (marble 
from to the next gravestone vendor). However, you have to make sure that 
it is isotopic homogeneous and this means some drilling and a quite 
large number of analysis since you can not use a material already tested 
by a lab you trust.

As far as I know IVA-Analytical, Germany [3] is in the process of 
preparing a calcite standard made from Cararra marble (Italy), which is 
close to NBS-19 in its isotopic composition (NBS-19 is also from there). 
Hopefully, it should be a suitable material for an internal lab calcite 
standard, since it was analyzed in different labs for its isotopic 
composition and homogeneity. This standard will probably come with a 
"value". However, every lab using it has to(!!) verify the value by a 
calibration against official reference materials like NBS-19.

greetings,
Robert


[1]
Coplen et al. 2006, New Guidelines for d13C Measurements. Anal. Chem., 
78 (7), 2439 -2441
Coplen et al. 2006, After two decades a second anchor for the VPDB d13C 
scale. Rapid Commun. Mass Spectrom. 2006; 20: 3165–3166
[2]
<http://www.iaea.org/programmes/aqcs/database/results/stableisotopes_result.html>
<http://www.iaea.org/programmes/aqcs/pdf/catalogue.pdf>
[3]
<http://www.iva-analysentechnik.de/en-vers/index.html>

-- 
Dr. Robert van Geldern
Section 3: Geochronology and Isotope Hydrology
Leibniz Institute for Applied Geosciences (GGA-Institute)

GEOZENTRUM HANNOVER
Stilleweg 2
30655 Hannover, Germany

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