Dear Listmembers,

We have stored aliquots of sample, working standards, and
reference H2 gases in sealed 3/8" pyrex tubing (filled using
a Toepler pump) for >5 years without measureable fractiona-
tions.  This is a reliable storage mechanism as far as we
have observed. Storing H2 in stopcock-sealed vessels and/or
with potentially reactive materials (as several of you have indicated)
for long periods (i.e., more than, say, 24 hrs) is not (100%) reliable.
Accordingly, we collect our sample H2 on activated charcoal in
ground-glass stopcock-sealed vessels, but analyze the gas within 1-2
hours of collection.

regards,