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I know there has been some discussion of clogged Finnigan Gas Bench needles
in the past but the Isogeochem Archive seems to be down so I can not check
it.  I have used my gas bench for hundreds of CO2-H2O equilibrations with
no trouble.  Now I am trying to run carbonates for the first time.  So far
I have found it easier to manually flush the vials and then manually inject
the acid.  After that I will use the autosampler to extract the CO2.  Just
as I was starting I managed to break the gas bench  needle by forgetting to
put the lid on the heating block.  So I installed a new needle (which was a
trial in itself trying to get the old graphite ferrule out.) Now after
running only about 10 samples the needle is clogged with crystallized
phosphoric acid.  I could easily see it in the needle with my hand
lens.  We have been attempting to inject the acid toward the edge of the
septum (away from where the sampling needle enters) and then wipe off the
drop of excess acid that seems to accumulate there.  There is also a drop
on the bottom side of the septum that we can not get at.

So I have two questions:

1)Has anyone had any luck unclogging the needle when it has acid in it?
2) What steps do I need to take to keep this from  happening again.?

Thanks

Andy



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Dr. Andrew R. Campbell
Professor of Geology
Department Chair
Dept. of Earth and Environmental Science
New Mexico Tech
Socorro NM 87801
Research office: 505-835-5327
Chairman's office: 505-835-5635
Fax:   505-835-6436
e-mail: [log in to unmask]
www.ees.nmt.edu
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