You can weakly influence the linewidth of the signal by changing the flip angle as per
https://pubs.aip.org/aip/jcp/article/99/10/7455/819616/Line-shapes-of-strongly-radiation-damped-nuclear
(Fig. 6), but not enough to matter, and in any case we=E2=80=99re more worried
about the dynamic frequency shift (see e.g.
https://pubs.acs.org/doi/10.1021/ja046208s
The latter paper implies a potential solution by applying weak presaturation of the
offending signal(s) too.
https://www.sciencedirect.com/science/article/pii/S1090780714002456?via*3Dihub
uses a related strategy by partially suppressing one of the peaks in such a way so as to
equalise the dynamic frequency shift across both peaks.
I=E2=80=99d always assumed that the difference between the ethylene glycol
and methanol data was because of different methods used to calibrate the temperature.
The most rigorous measurements currently available take into account the effect of
the magnetic field on the apparent Pt100 temperature (
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/full/10.1002/mrc.5216, and at least so far, are only available for MeOH-d4.
These differ slightly from those currently implemented in TopSpin/calctemp
(although potentially within any inevitable temperature gradients), which make
use of the older calibrations in
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/mrc.1941.
It=E2=80=99s a fairly trivial modification of calctemp if you want to
do it yourself, but happy to share if anyone wants it.
If deuterium sensitivity allows, you might consider making yourself a (flame-sealed,
anhydrous) ethylene glycol sample and calibrating your temperatures on the natural
abundance 1D deuterium spectra as per
https://www.sciencedirect.com/science/article/pii/S1090780705001680.
On my 400/2010 BBFO the deuterium sensitivity is nowhere near good enough, but it
might be viable on your system.
The other thing to consider is that the set point of your spectrometer is reproducible
enough that you could run the experiments on uncorrected temperatures, and then go back
and calibrate your temperatures when the ethylene glycol-d6 sample becomes commercially
available.
As long as you cite your temperature calibration method clearly in any experimental,
I don=E2=80=99t think anyone can complain too much because maybe they=E2=80=99re all wrong =F0=9F=98=8A.
Clemens what sort of availability will the ethylene glycol-d6 be when it=E2=80=99s ready?
Given we=E2=80=99ve historically not had a proper high temperature sample for the longest time,
I can imagine there being quite the demand among NMR facilities worldwide=E2=80=A6myself included.
Given the current costs of ethylene glycol-d6 from e.g. CIL and the difficulty in drying it properly,
I can also anticipate it being somewhat more expensive than the regular MeOH-d4 sample =E2=80=93
care to comment on order of magnitude?
Thanks
Geoff
> From: main_at_ammrl.groups.io <main_at_ammrl.groups.io> On Behalf Of Clemens Anklin via groups.io
> Sent: Wednesday, August 23, 2023 12:21 AM
> To: main_at_ammrl.groups.io
> Subject: [External] Re: [AMMRL] 99.8% MeOD vs 80% Ethylene Glycol
The original equations go back to Merbach et al in JMR 46, 319-321 (1982).
Over time they have been refined. The equation for Glycol-d6 is experimentally
determined. The same is true for MeOD 99.8%.
Clemens
On 8/22/2023 12:52 PM, Zhang, Weixing via groups.io wrote:
Dear All,
Thanks to everyone who has read and replied to my email.
We want to use a CryoProbe to run experiments at different temperatures up
to 90 oC (363 K).
Many people think that radiation damping of 80% ethylene glycol is the problem.
Massively detuning the cryoprobe or using deuterated ethylene glycol should
give more accurate results.
Clemens told me that the Bruker part number of 99% ethylene glycol-d6 is Z10629.
Z10629 is currently under development in Germany and it would be about a month
for it to be completed.
The Bruker AU program calctemp has these options.
I am curious where Bruker got the equations from, and I would greatly appreciate
any information.
With warm regards,
Weixing Zhang (Walter)
Research Operation Manager
Biomolecular NMR Spectroscopy Center
St. Jude Children=E2=80=99s Research Hospital
Memphis, TN 38105
USA
> From: main_at_ammrl.groups.io<mailto:main_at_ammrl.groups.io> On Behalf Of Clemens Anklin via groups.io
> Sent: Friday, August 18, 2023 2:26 PM
> To: main_at_ammrl.groups.io<mailto:main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] 99.8% MeOD vs 80% Ethylene Glycol
Hi Weixing
if you do this on a cryoprobe this will be the expected result. 80% Glycol gives
a massive amount of radiation damping. This leads to different readings as shown
by Stefan Berger in
https://doi.org/10.1002/mrc.1941
You can try to run a more accurate measurement by massively detuning the probe.
With best regards
Clemens
On 8/18/2023 3:09 PM, Walter Zhang wrote:
Dear All,
I need to use 80% Ethylene Glycol for high temperature calibration. [cid:image003.png_at_01D9D5A6.9835F260]
Before I do the calibration, I compared it with 99.8% MeOD at 303 K.
When I set temperature to 303 K,
99.8% MeOD gives 303.03 K while 80% Ethylene Glycol gives 300.57 K
The difference between the two calibration samples is 2.46 K.
Is this normal?
Your comments are appreciated!
Best regards,
Weixing Zhang
St. Jude Children=E2=80=99s Research Hospital
Memphis, TN 38105
USA
________________________________
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