Hello again,

I suppose that for the sake of thoroughness I should tell
you that the acidic water we want to measure H/D isotope
ratios in also contains about 20 000 ppm of dissolved
solids. However this or much higher salinities are not a 
problem for us as we inject our water samples through a
7 micron filter which the salts precipitate on. Also we
routinely run a lot of water samples and never get
incomplete reactions; and there was no evidence of water
being present during the mass spec runs.

Thanks again for the advice I already received.

Natalie