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Jeff,

 I can not help with the chemistry issues but can tell you how I deal with this type of problem. I use inserts without slots and change them more often. If you change them every 50 runs they hopefully will not be so destroyed. When I remove them and if the business end is not totally damaged I use it again but put it in the opposite direction so damaged end is at the top. That way one insert is good for  2 sets of runs. When I change it out I put a different one in so I can start running again quickly. Then I Let that one cool off and determine how to use it next. It is not much more work and may be less cost. Every type on sample is different but I have found if your sample weight it is low it works for most applications. Any questions you can give me a call.


Mike Elefante, President
Elf Analytical Services, Inc
732-922-8400
 



-----Original Message-----
From: Jeff Havig <[log in to unmask]>
To: ISOGEOCHEM <[log in to unmask]>
Sent: Sun, Feb 19, 2017 2:06 pm
Subject: [ISOGEOCHEM] EA insert fusing to oxidation column

Hello Analytical Experts-

I am running a Costech Elemental Analyzer attached to a Delta V Advantage IR-MS, and have been having issues with the combustion chamber quartz insert fusing to the oxidation column (we have had to the replace the oxidation column three times now because of this, and this is less than ideal).

Our setup:
The insert has ~ 1 cm of quartz wool at the bottom with ~2-3 mm of Chromium(III) oxide on top of that. I have been using the medium (5x9 mm) tin capsules for loading samples (49 per run, 2 to 3 runs per insert). The samples I have been running include volcanically-derived glacial sediments, snow algae, and hot spring biofilms (mostly composed of amorphous silica). Some of the samples have been acidified with HCl to remove DIC and carbonates, but have all been rinsed with 18.2 MOhm/cm water to remove all Cl- before drying and grinding.

It seems as though the insert quartz is fluxing and being stripped away, enlarging the slit openings and weakening the insert, allowing the tin to leave the side slits and fuse the insert to the inside wall of the oxidation column. Also, there seems to be a tendency for yellow-ish melt/precipitate to form at the bottom of the insert, fusing it to the oxidation column there as well. I have attached an image (pdf) of the last failure with examples of what I am trying to describe.

The temperature of the combustion chamber/oxidation chamber is at 1000 C (checked with thermocouple). This has happened a few times in the past, but never consistently like this.

If any of you happen to have had this problem and might know 1) what is going on, and 2) the best way to fix the problem, I would be eternally grateful for your time and help.

-Jeff

-- 
Jeff Havig, Ph.D.
Adjunct Faculty
Room 517
Geology-Physics Building
Department of Geology
McMicken College of Arts and Sciences
University of Cincinnati
Cincinnati, OH 45221-0013


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