Re: [AMMRL] 99.8% MeOD vs 80% Ethylene Glycol

From: Mark Swanson <mark94131_at_gmail.com>
Date: Thu, 7 Sep 2023 11:24:34 -0700

Hi Everone,

Does the issue with Ethylene Glycol also apply to N2 cryoprobes (e.g.
Prodigy) or is it mainly Helium cryoprobes? Also, under 'edte' there's a
measured value and a corrected value. Does anyone know how good the
correction is in general, or does it vary from probe to probe?

Thanks,

Mark


On Wed, Aug 23, 2023 at 4:17 AM Akien, Geoffrey <g.akien_at_lancaster.ac.uk>
wrote:

> 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’re more worried
> about the dynamic frequency shift (see e.g.
> https://pubs.acs.org/doi/10.1021/ja046208s
> 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’d 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’s 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’t think anyone can complain too much because maybe
> they’re all wrong 😊.
>
>
>
> Clemens what sort of availability will the ethylene glycol-d6 be when it’s
> ready? Given we’ve historically not had a proper high temperature sample
> for the longest time, I can imagine there being quite the demand among NMR
> facilities worldwide…myself 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 – care to comment on order of magnitude?
>
>
>
> Thanks
>
>
>
> Geoff
>
>
>
> *From:* main_at_ammrl.groups.io <main_at_ammrl.groups.io> *On Behalf Of *Clemen > 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’s Research Hospital
> Memphis, TN 38105
> USA
>

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Received on Thu Sep 07 2023 - 12:30:15 MST