Dear Bill,

Not sure if this is any consolation to you but I have found over the years
that the quality of the chemicals that are used in both the oxidizing and
reduction furnaces, not to mention the anhydrone in the water trap have
actually acted like a chromatographic column and caused tailing? I don't
know why anhydrone would do this (?) but it is something to consider. I'm
not talking about spent chemicals, I'm talking about brand new stuff right
out of the bottle. I traced this one down after a week of beating my head
against the wall, changing gases, repacking columns, etc. Just changing the
manufacturer of the anhydrone fixed the problem. ???? Right! It is really
bad when you can't even count on the chemicals! Most of the manufacturers
tout thier product for the CHN crowd, but often what is good enough for
them, isn't good enough for isotope work! For what its worth I use 5.0
helium and have never had a problem with it.

Best of luck,

Douglas "Cap" Introne
Research Associate Professor/Laboratory Director
Stable Isotope Laboratory
Sawyer Environmental Research Center
University of Maine
Orono, ME 04469

Tel. (207) 581-2192
Fax (207) 581-3490
E-mail [log in to unmask]