>
>And how do you make an activity correction for salty samples to make
>18Owater-CO results directly comparable to conventional CO2-water
>equilibrated assays?  To my knowledge this angle has never been
>satisfactorily resolved, at least not yet.  Everyone should get a copy of
>NIST report 260-149 by Verkouteren and Klinedinst (Dec 2003) on value
>assignment and uncertainty for SI refs (waters, carbonates).  If we,
>collectively, cannot even get 18O-waters by conventional equilibration
>right on, then goodness knows what trouble less precise decomposition
>techniques will bring!



Dear LW and others,

The reduction method has one huge advantage over other techniques in that
sub-microliter samples can be analyzed.  It is true that for larger
samples, the shaker method works great.  As for salinity, we demonstrated
that salinity has no effect -- as expected -- on the d18O values of waters
using carbon reduction.

Sharp, Z.D., Atudorei, V. and Durakiewicz, T. (2001) A rapid method for
determination of hydrogen and oxygen isotope ratios from water and solid
hydrous substances. Chem. Geol. 178 , 197-210