I suspect some sulfurous compounds. Do you have silver wool at the bottom of your combustion reactor? I suggest a good cm or two, more than normal. Change it frequently. Marilyn

From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Matheus Carvalho <[log in to unmask]>
Reply-To: Stable Isotope Geochemistry <[log in to unmask]>
Date: Sunday, January 31, 2016 at 2:44 PM
To: "[log in to unmask]" <[log in to unmask]>
Subject: tubes cracking in the chromium oxide band

Dear all, I have been analyzing some sediment samples from mangroves for C and N isotopes on a Flash EA - Delta V plus setup, and I have noticed that after running a number of them (about 50) the oxidation tube cracks at the chromium oxide band. This does not happen with any other samples. In addition, these same samples tend to clog the stainless steel lines, and apparently also damage the gc column. Not the kind of sample I wish to run often. Does anyone have an idea of the possible reason for such phenomena?
Thank you,

Matheus C. Carvalho
Senior Research Associate
Centre for Coastal Biogeochemistry Research
Southern Cross University
Lismore, NSW, Australia