Thanks, Paul.We're currently running at 1450, so I'm hesitant to get hotter. Deactivation seems like a possibility though, especially given the high temp we're running. Based on some of the reading I've done in the archives (too much vs. too little graphite in the reactor), it seems like an easy way to mess up the results. I'm going to recondition (deactivate) the reactor and see if that changes anything.Best,--On Tue, Jan 17, 2017 at 12:09 PM, Paul Eby <[log in to unmask]> wrote:
If your sample peaks show a size effect and your ref peaks don’t, then the answer could be in the reactor. If the conversion process is incomplete, you could easily get this result. You could try increasing the reactor temperature or looking at the whether the tube is sufficiently deactivated.
I’m also curious about the dilution series that you run: are you changing the concentration of the standard, or perhaps are you changing the split flow to change the peak height?
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I've got an older GCC III that I have to manually adjust.
So, if I do a series of on/offs, 8 refgas peaks, of increasing size from 1 V to 10 V I get a much smaller effect of ~ 0.3 permil/V with an H3 of ~ 3.2 applied. This same H3 is applied to my alkane standards, but I still have the effect I described above.
JeffTwo things are infinite: the universe and human stupidity; and I'm not sure about the universe. - Einstein
Jeff Salacup, Ph.D.Stable Isotope & Biogeochemistry Lab ManagerUMass-Amherst