Hello Robert,
My website with Excel Spreadsheet has been popular for this, including using 2H observe. It is still on my old website, and is still the #3 Google hit for “NMR Sample Temperature Calibration”, at
http://chemnmr.colorado.edu/manuals/temperature-calibration.html . My Old web-server (the one that once operated the AMMRL list) is still up and running, even though I haven’t been there to maintain it since I left the University last October.
It might be complementary to your recent calibrations, and it’s a pretty handy spreadsheet. I did the 2H observe calibration myself at the Univ. of Nebraska many years ago, and this spreadsheet has been a pretty popular download ever since.
Best wishes,
-Rich Shoemaker
Bruker BioSpin Corporation
________________________________
Richard K. Shoemaker, Ph.D.
Technical Sales Representative, Northwest & Central North America Region
Denver, Colorado
Phone: 720-296-9730
richard.shoemaker_at_bruker.com<mailto:richard.shoemaker_at_bruker.com>
www.bruker.com<
http://www.bruker.com/>
From: Robert Peterson [mailto:peterson_at_mbi.ucla.edu]
Sent: Thursday, June 01, 2017 3:29 PM
To: AMMRL
Subject: AMMRL: temperature calibration by neat methanol and deuterated methanol
Dear group,
Some of my users had reason to suspect that the temperature calibration on one of our older instruments (with cryoprobe) was wrong. I've always calibrated the temperature using pure methanol, but one of our users said she had read that deuterated methanol is supposed to be better for cryoprobes. The Bruker calctemp au program references this paper for using deuterated methanol to determine temperatures:
Magn. Reson. Chem. 2007; 45: 175-178
And they do indeed claim that deuterated methanol gives better results on cryoprobes than neat or concentrated solutions of methanol.
I decided to calibrate the temperature using both neat methanol and methanol-d4. I took measurements with both samples at set temperatures from 284K to 323K, at 3 degree intervals.
I analyzed the methanol-d4 data with the formula from the above paper (T = 419.1381 - 16.7467*delta^2 - 52.513*delta).
I analyzed the neat methanol data four different ways. I used three separate quadratic formulas, one of which is from the Bruker VT manual. And I also used the linear approximation from the Bruker VT manual for temperatures between 265-313K. These four methods for neat methanol gave nearly identical results.
See the attached figures. They show the results from methanol-d4, and neat methanol calibrated using the linear approximation from the Bruker VT manual. The temperatures 314K and lower are different by 6 - 7 degrees between the two methods! Is this possible? Has anyone else tried this? I haven't had the chance to try this on my other instruments*, so I don't know what the result will be. But now I'm wondering if most of our temperatures have been drastically off ever since we started using cryoprobes.
*We have a new (two year old) Avance III HD console on one of our instruments. The installation engineer did a temperature calibration on that one using deuterated methanol. So apparently, Bruker does use deuterated methanol to calibrated temperatures on cryoprobes.
Thanks and I will post a summary of the responses.
-Robert
--
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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<mailto:peterson_at_mbi.ucla.edu>
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Received on Fri Jun 02 2017 - 15:25:05 MST