Hi Toti, I'm sure Willi (Brand) can shed some light on your observations with glassy carbon at temperatures below 1300 C for 18O analysis. Personally, I figure it might be a case of the Boudoir equilibrium for CO2 <-> CO being shifted towards higher temperatures for 90%+ CO yield in systems where (a) the product is continuously removed and (b) reactants are moving pretty fast given the high He flow rate in the furnace. I am running our TC/EA at 1400 C for 2H and 18O analysis and have experienced no problems (we are using IAEA-OH1 to OH4 as standards). Ditto when running organic materials. Only exception thus far are nitrates; here I found the optimum temperature for 18O (in terms of consistent results for the IAEA-NO3 standards) to be 1350 C. That's the "lowest" temperature I have run our TC/EA since higher temperatures seems to be counterproductive for 18O of nitrates. Cheers, Wolfram > -----Original Message----- > From: Stable Isotope Geochemistry > [mailto:[log in to unmask]] On Behalf Of tlarson > Sent: 31 May 2005 21:17 > To: [log in to unmask] > Subject: Related Hi temp EA question > > > Folks, > > I'm shopping for a new EA to lighten the work load of my > current one (Euro > EA) that we use for typical EA stuff: basically CN isotopes > and ratios in organics. We also run a lot of waters using > chrome reduction at 1075°C. I'm considering a high temp that > will be used solely for glassy carbon reduction in solid > samples and chrome HD for water. > > Question: > I've run oxygen using glassy carbon at lower temps (1100°C), > but wasn't thrilled with the results. Interestingly, at > 1250°C the results were worse. Is life really that much > better at 1400°C for glassy carbon? Aside from the Finnigan > TCEA, what other high temp EA brands have folks had good success with? > > Thanks, > Toti > > > > Toti Larson Ph.D. > Los Alamos National Laboratory > Earth and Environmental Sciences 505.667.9894 (lab) > Los Alamos, New Mexico 87545 550.667.8006 (office) >