It might be easier to use this product:
https://www.cortecnet.com/us/ne-h5-3-micro-nmr-sample-tubes-varian-5-3mm.html?___store=us_storeview&___from_store=default
***********************************
Dean L. Olson, Ph.D.
Director, NMR/EPR Lab
146 Roger Adams Lab
School of Chemical Sciences
U. of Illinois at Urbana-Champaign
600 S. Mathews, Box 31-1, MC-712
Urbana, IL 61801 USA
Lab: 217-244-0564; Cell: 217-722-9432
dolson_at_illinois.edu
http://scs.illinois.edu/nmr
http://scs.illinois.edu/epr/
***********************************
> From: main_at_ammrl.groups.io On Behalf Of george gray via groups.io
> >Sent: Tuesday, June 24, 2025 12:32 PM
To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] New Error on Varian 400MR
Using a smaller diameter sample (3mm sample inside of a 5mm probe) can have
a dramatic reduction of the salt effect. If you have a 3mm turbine, just use
that turbine for a 3mm tube. You will, of course, have a hit on filling
factor, but the tuning should be closer to that of a non-lossy sample, so
you'll not suffer the full loss. You might be able to tune the probe properly
and determine the 90-degree pulse length.
If you don't have a 3mm spinner turbine you can place the 3mm sample inside
a 5mm tube. I recall doing this many, many years ago when I had to have a
13C lock signal to do time averaging to do 13C (cw!) observe on a 100MHz
(proton) spectrometer. The S/N ratio was about 2 for this lock, but it did
work. I recall using a thin piece of teflon, cutting out triangles that would
fit inside a 5mm tube and then punching out holes for a 2mm capillary
containing the enriched carbon disulfide.
A side benefit for the 3in5 approach is that you can use any lock solvent
(non-salty organic, for example) in the outer space.
On 6/24/2025 9:33 AM, Vander Velde, David via groups.io wrote:
Yes, assuming that's the 1H match control on your system (it's channel 6 on
mine). High ionic strength samples drive the match towards its minimum value,
and once you reach that in a particular probe, you're out of luck with getting
the sample properly matched.
Setting aside the question of whether it's necessary or advisable to prepare
a sample like that, you can still get some kind of 1H spectrum by skipping
probe tuning, taking some big hit on sensitivity. Some experiments are not
going to work or not advisable, like 13C with 1H decoupling—you'd get
high reflected power back from a mismatched probe, and the normal decoupling
parameters will fail.
________________________________
> From: main_at_ammrl.groups.io on behalf of Stephen Nolte via groups.io
> Sent: Tuesday, June 24, 2025 8:13 AM
> To: main <main_at_ammrl.groups.io><mailto:main_at_ammrl.groups.io>
> Subject: [AMMRL] New Error on Varian 400MR
Hi all,
Summer research students elicited a new intermittent error this week on our
Varian 400MR failed - rf signal too weak on tune chan#5.
Can this be related to high levels of ionic salts in the sample?
Thanks!
_______________________________
Stephen Nolte | Chemistry Technician
Millersville University
717-871-7413
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Received on Tue Jun 24 2025 - 15:51:01 MST