Isotope ratio mass spectrometers are not truly specialized to measure
isotope ratios at natural abundance only. The resistors of the
amplifiers are only selected to make such measuremetns as good as
possible. Exchanging resistors is easy and therefore any given ratio can
be measured with very good precision. But; what is good precision. This
mostly depends on the question you are investigating. Technically there
is only one major problem. THERE ARE NO STANDARDS FOR NON-NATURAL
ABUNDANCE that are well enough characterized and have the support of the
community.
Regards    Willi

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Willi A. Brand, Stable Isotope Laboratory       [log in to unmask]
Max-Planck-Institute for Biogeochemistry
Carl-Zeiss-Promenade 10, 07745 Jena, Germany    Tel   +49-3641-643718
P.O.Box 100164, 07701 Jena, Germany             Fax:  +49-3641-643710
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