Dear all,

since November last year I have been measuring hydrogen isotopes
using Indiana zinc and following the off-line procedure described by
Hayes and Johnson (1988).

After some very successful first weeks the precision suddenly became
intolerable (I think it was on a Monday), and for about two months I
was trying to find the problem. In February I managed to get back to
satisfying results (without really changing the procedure). The other
person in the lab doing the same preparation, however, is still
producing differences on the order of 50 permil between double
preparations - and she is doing exactly what I am doing (she
swears!). I hope this is not a question of "mind over matter" in
isotope geochemistry ; )

My feeling today is that extreme care must be taken to avoid any
water vapour on the surface of the glass tubes - I now heat them to
500°C and do not allow them to cool to less than 110°C until they are
filled with the Zn and attached to the vacuum line. Apart from
that, I have no idea why it has to be me who is doing the
preparation - one might sum up the story as: "I am producing good
results, but I don't know exactly why"... Are there any other crucial
details in the preparation, or any tricks of the trade that might
help a newcomer like me?

Frank Pawellek




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Frank Pawellek
Institut fuer Geologie
Lehrstuhl fuer Sediment- und Isotopengeologie
Ruhr-Universitaet Bochum
Universitaetsstrasse 150
44801 Bochum
Germany
Phone: +49-234-700-5458
Fax: +49-234-7094-571
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