Hi All,

I am a beginner on TC/EA. Your advice will be very helpful!

The story is....we have been trying to set up a method of dD measurement with silicate minerals (dD only, not d18O).
I think that the method is fine...

The problem is...when I reduced reactor temperature to change the C crucible, I found both ceramic tube and glassy C tube were cracked. 
This happened twice in a row. I reduced the temperatures of reactor slowly at the rate of 50C/20-30mins.
The cracking was on the hot spot (both incidents).
There was dark gray-black material built on the surface of glassy carbon (hot spot). 
I think this is the carbide, which other users mentioned before?
This time, the glassy C tube (at the hot spot) got thinner and had a small hole.
I do not see the expansion of ceramic tube though. 
It looks like that there was some reaction going on. 
I only ran biotite and muscovite with this packing. 
When I ran silver phosphates a few years ago, this did not happen. 
Anyone had same problem? Then, how did you solve this problem?

One curiosity as the beginner is that I was wondering if anyone tried the analysis with ceramic tube only (no glassy carbon)?
I am interested in hydrogen isotope only (not oxygen isotope). 
What if I pack the ceramic column with glassy carbon chips, and add nickelized carbon powder in sample Ag cups? 
Then, I have to change the bottom feeding setup to the standard setup. Right now, we have the bottom feeding setup.

Thank you.