I would like to thank everyone for their responses. For the most part, many others have used epr tubes successfully for NMR experiments. So as a summary:
- EPR tubes tend to have lower tolerance than NMR tubes. Some tubes have different widths from top to bottom. EPR tubes do have a camber and concentricity that is worse than any of the NMR tubes. These numbers are worse by a factor of 2 compared to really cheap NMR tubes and about four times worse than good tubes. This may cause tubes not to fit properly into the spinner, so different tubes might have to be tried first. If one does fit, do not spin it in the probe, just in case it is not concentric enough for stable spinning.
- There are some EPR better tubes available. Wilmad has EPR tubes that have similar precision as NMR tubes (722-PQ-7 is a precision 7" Suprasil tube) although a little pricy.
- Workaround: An interesting work around that was suggested by Ken Belmore is to use a 4mm EPR tube and slide it into a 5mm NMR tube. This takes care of finding the right tube that would fit in the spinner. An external solvent could be put into the 5mm tube for locking purposes and shimmed manually.
I tried the 4mm EPR tube in a 5mm NMR tube and it seemed to have worked nicely. Although the 4mm EPR tube has a smaller sample volume size, it was not much of an issue since the sample could be made fairly concentrated. It locked nicely on the external solvent and manual shimming was not too much of a problem. The line shape was a little broad, however major splittings can still be seen.
Thanks again for all your help and suggestions.
Regards,
Joel
From: Joel Tang [mailto:joel.tang_at_jhu.edu]
Sent: Thursday, May 07, 2015 4:31 PM
To: ammrl_at_ammrl.org
Subject: AMMRL: Using EPR tubes for NMR experiments
Hello AMMRL Members,
I am wondering if anyone has ever tried using an EPR quartz tube for NMR experiments. If so, have you had any problems (interference, distortions, shimming problems etc.)? I am also concerned about the precision of the EPR tubes compared to NMR tubes.
A student is interested in acquiring NMR data (1H and 13C) before and after a sample is irradiated with UV light. The student would like the sample to be in a quartz tube for UV spectroscopy as well. Since their sample is extremely air/moisture sensitive they want to keep it in the same sample holder for both experiments to minimize exposure to the atmosphere. Since they do not plan on doing these types of experiments often, they do not want to invest in a quartz NMR tube (other groups have 5mm EPR tubes that they can borrow).
Any input would be appreciated.
Thanks,
Joel
------------------------------------------
Joel A. Tang, Ph.D
Core Facility Manager - NMR,
Department of Chemistry
Johns Hopkins University
tel: 410-516-7456
nmr.chm.jhu.edu
Received on Mon May 11 2015 - 09:20:13 MST