Dear All,

I am currently running enriched water samples containing enriched levels of D
and 18O of up to +1000 ppm (relative to SMOW).  I am reliably informed by Steve
Crowley, and others, that it is unwise to assume linearity of the mass spec over
this range making SMOW, SLAP and GISP unreliable standards.  Does any one know
of a reliable method of creating enriched standards or a source where they could
be purchased.  Thanks.



Simon



Dr Simon Davis
Liverpool JMU energetics lab
B.E.S
Liverpool John Moores University
Liverpool
England
L3 3AF