AMMRL: temperature calibration by neat methanol and deuterated methanol

From: Robert Peterson <peterson_at_mbi.ucla.edu>
Date: Thu, 08 Jun 2017 16:44:01 -0700

Dear group,

Thanks for all the replies. Most people agreed that the effect could be
caused by radiation damping, and that using deuterated methanol is
preferred. I also had a couple of suggestions to put a thermocouple into
an NMR tube and measure the temperature directly.

However, there is now more to the story. I've now run temperature
calibrations using both protonated and deuterated methanol on all of my
spectrometers. The behavior is surprising, and different for each of
them. See the attached figures. On our 500 (the one I wrote about last
week), the calibrations using MeOH-H and MeOH-D are different by 6 - 7
degrees, and the MeOH-D calibration is 8 - 9 degrees different than the
set temperature. But on our 600, the two calibrations are very close to
each other, and only 1 - 2 degrees away from the set temperature. And on
our 800, the two calibrations are again very close to each other, but 6
-7 degrees away from the set temperature.

Whatever causes the problem on the 500, it doesn't seem to be radiation
damping. It must be some instrument specific effect. Does anyone have
any ideas what could cause this?

All instruments have cryoprobes. The 500 is a DRX (console: 1996,
cryoprobe: 2007). The 600 is an AV III HD (console and cryoprobe: 2015).
The 800 is an AV I (console: 2004, cryoprobe: 2007).

thanks,

-Robert

-- 
-----------------------------------------------
Robert Peterson, Ph.D.
Facility Manager - NMR Technology Center
UCLA-DOE Institute for Genomics and Proteomics
UCLA Dept. of Chemistry and Biochemistry
phone: (310)825-1816
fax:   (310)825-0982
peterson_at_mbi.ucla.edu
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Received on Thu Jun 08 2017 - 13:50:55 MST