Hello Walter,
Obviously this is a larger discrepancy than any of us would like to see.
It depends in part to what equation(s) are you using to convert the
chemical shift separation between the peaks in your 1H-NMR spectrum to a
sample temperature.
But I think the real challenge might come down to the broadness of the
signals for the 80% ethylene glycol standard. That was one of the clear
benefits of the 99.8% methanol-d4 standards, especially at higher field
and with cryoprobes. I don't know if there is a comparable standard for
high temperature, so I guess you are stuck with the 80% EG standard
unless someone knows of a better standard.
How high a sample temperature do you plan to use? If it is less than
320 K, then you can probably stick with the 99.8% methanol-d4. If you
are going to higher temperature, then I guess you could use the 80% EG
standard solution, and be sure to report that is how you were determined
the temperature.
Good luck,
Bob.
On 2023-08-18 3:09 p.m., Walter Zhang via groups.io wrote:
>
>
>
> Dear All,
>
> I need to use 80% Ethylene Glycol for high temperature calibration.
>
> 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’s Research Hospital
> Memphis, TN 38105
> USA
>
>
> ---------------------------------------------------------------------=
---
>
>
>
--
Dr. Bob Berno
Manager, NMR Facility
McMaster University, ABB-156
1280 Main St. West
Hamilton, ON L8S 4M1
T: 905-525-9140 x24158 or x24686
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Received on Fri Aug 18 2023 - 16:44:22 MST