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Hi Jeff,

We haven't used ash inserts for a while in our lab due to the reasons you mention. We vacuum ash out with a simple setup originally described by Paul Brooks at UC Berkeley. Our vacuum setup uses a small diaphragm pump, some 1/2" stainless tubing with teeth filed in the end and two vacuum flasks (second one filled with glass wool to stop fine particulates). We vacuum at a count of 50-500 depending on the samples dropped. Running sans insert can give you the most possible ash volume and you can remove ash at any time without being concerned about getting a certain mileage out of an insert. The teeth on the stainless tubing work well to grind through any sample residue and even broken off inserts. And then it is just a simple dump of the flask into your waste container.

We have easily run reactors past 1000 samples with our vac technique, but I'm not sure if this would be as trouble free with your samples.

Ben


Benjamin Harlow
Manager, Stable Isotope Core Laboratory
Washington State University
367 Eastlick | Pullman, WA  99164-4236
Office: 509-335-6161 | Lab: 509-335-6154 | Fax:509-335-3184
http://www.isotopes.wsu.edu<http://www.isotopes.wsu.edu/>



From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Jeff Havig
Sent: Sunday, February 19, 2017 11:07 AM
To: [log in to unmask]
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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