Hello Rob and others,
The flash is inconsistent. At times it is great and other time
essentially non-existent. Interestingly the d13C value is always
lower (i.e., closer to what I expect) when the flash is good. I've
tried increasing the amount of oxygen but the results were
inconsistent. Your suggestion that the problem may be with the
diaphram is a good one. It was changed about a year ago ... maybe
it is time again. That will be tomorrows job.
Thanks for the help,
Jennifer
>Dear Jennifer,
>Oxygen injection is the first suspect that comes to mind. If there really is
>flow of oxygen through the bimatic valve (can you measure this?), then I
>would check the diaphram of the bimatic valve: cool furnaces, turn off air
>and gases and then undo the top of the valve with a 6 mm hex. key (you might
>need a "crescent" spanner on the hex key for extra persuasion). Even if the
>diaphragm is not actually holed, I suspect that ours sometimes sticks,
>reducing the flow during O2 injection.
>You should of course always get the nice bright flash on sample drop.
>Robt.
>----- Original Message -----
>From: "Jennifer McKay" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Monday, February 14, 2005 10:02 AM
>Subject: [ISOGEOCHEM] Combustion Problem
>
>
>>Hello Everyone,
>>
>>I have a problem with the Carlo Erba NA-1500 elemental analyzer that
>>is attached to our Isoprime mass spectrometer. The combustion of
>>samples appears to be incomplete. As a result the precision is very
>>bad and when we run empty tin cups we observe a very high background.
>>The high background problem disappears if I put in a new reaction
>>column, but reappears after about 50 samples. I can obtain
>>consistent results for my standards if I run an empty tin cup between
>>each, but this is not an acceptable solution. As far as I can tell
>>the combustion temperature is OK (1020 °C according to the readout)
>>and none of the parameters (i.e., sample drop time, oxygen flow etc.)
>>have been changed. Is it possible that the furnace for the reaction
>>column is dying?
>>
>>I would appreciate any suggestions regarding how I might solve this
>>problem.
>>
>>Yours truly,
>>Jennifer.
>>
>>------------------------------------------------------
>>Jennifer Mckay
>>Agente de Recherche / Research Associate
>>GEOTOP - Universite du Quebec a Montreal
>>C.P. 8888, succursale Centre-Ville
>>Montreal, Quebec, Canada
>>H3C 3P8
>>
>>Telephone bureau/office: 514-987-3000 (poste/ext 2413)
>>Telephone lab: 514-987-3000 (poste/ext 7028)
>>Telephone GEOTOP: 514-987-4080
>>Telecopieur/Fax: 514-987-3635
>>E-mail: [log in to unmask] or if that fails try [log in to unmask]
>>------------------------------------------------------
------------------------------------------------------
Jennifer Mckay
Agente de Recherche / Research Associate
GEOTOP - Universite du Quebec a Montreal
C.P. 8888, succursale Centre-Ville
Montreal, Quebec, Canada
H3C 3P8
Telephone bureau/office: 514-987-3000 (poste/ext 2413)
Telephone lab: 514-987-3000 (poste/ext 7028)
Telephone GEOTOP: 514-987-4080
Telecopieur/Fax: 514-987-3635
E-mail: [log in to unmask] or if that fails try [log in to unmask]
------------------------------------------------------
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