Dear Tonu,

As we discussed, I send you my procedure described below.
The procedure I use for water samples:
- put 100 mg Zn into 6 mm pyrex (or simax, this is a Czech
equivalent) tubes
- pump the tubes and heat the zinc until it starts evaporating, then
pump until
good vacuum is reached again,
- let dry air into the tubes, detach from the vacuum line, drop a
piece of
capillary containing the water sample immediately, and attach to the
line
- freeze with LN2 for 2-3 min, then pump
- flame-seal the tubes.

I hope this helps. Additional information about the zinc amount
effect is in Demeny (1995,  H isotope fractionation ..., Chem.
Geol., 121,
19-25.). In short, when impure waters are analysed, a solution is to
put more zinc into the reaction tubes. However, I found that
changing the zinc amount with the same water quantity changes the
dD value obtained.

Best regards,
Attila

Dr. Attila Demeny
Laboratory for Geochemical Research
Hungarian Academy of Sciences
Budapest, Budaorsi ut 45, H-1112, Hungary
tel/fax: 36-1-319-3145
e-mail: [log in to unmask]