In addition to what has been already suggested I would: 1) Not put any quartz wool on top of the Cr oxide in the combustion/oxidation column; just add 1 more cm of Cr oxide so the quartz insert sits on it, 2) Put less quartz wool (~0.5 cm) but more Cr oxide
(0.5 cm) on top at the bottom of the quartz insert, 3) Open/unscrew the purge valve on the autosampler lid very gently, and 4) Use the smallest amounts of sample as possible. We had similar issues 5 years ago and removing the top quartz wool plug from the
combustion column made a big difference. Cheers. Mihai
Dr. Mihai Lefticariu
Mass Spectrometry Facility
Southern Illinois University Carbondale
Carbondale IL 62901
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 Havig, Ph.D.
Adjunct FacultyRoom 517Geology-Physics BuildingDepartment of GeologyMcMicken College of Arts and SciencesUniversity of CincinnatiCincinnati, OH 45221-0013
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