If David is correct and it is the probe insert, another fast way to check the
insert is by doing a simple imaging experiment (so long the probe has Z
gradient) using the pulse program imgegp1d2h. I believe the parameter set is
gradshim1d2h. With a sample in the magnet, rga, zg, then process using ft and
then mc. It is very fast and easy.
You get pretty much a broad hump that extends to the left and right limits of the
window. If the hump is not smooth (visually – and often peak picking will
locate more than one “peak”), then either the insert is broken, or
the insert is very dirty, or your sample is not homogenous.
I use this experiment all the time for troubleshooting.
Another use for this experiment:
When using IconNMR (automation), part of my shim program tests if the sample
solvent is DMSO.
If so, then this imaging is run before data acquisition to confirm that the
DMSO doesn’t have solids in it (from freezing).
Cheers
George
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George Sukenick, Ph.D.
Associate Lab Member/Head
NMR Analytical Core Facility
Sloan Kettering Institute
Memorial Sloan Kettering Cancer Center
417 E. 68th St ZRC 2164
New York., N.Y. 10065
Main: (+1) 646-888-2237
g-sukenick_at_ski.mskcc.org<mailto:g-sukenick_at_ski.mskcc.org>
From: <main_at_ammrl.groups.io> on behalf of "Vander Velde, David" <davidv_at_caltech.edu>
Reply-To: "main_at_ammrl.groups.io" <main_at_ammrl.groups.io>
Date: Wednesday, August 2, 2023 at 11:30 AM
To: "main_at_ammrl.groups.io" <main_at_ammrl.groups.io>
Subject: [EXTERNAL] Re: [AMMRL] tuning range shifts on BBFO probe
In my experience, a cracked or broken probe insert is the commonest cause of
probe tuning changes. A useful tool for checking on the condition of the inserts
and coils is a borescope/endoscope camera. I have one with a 3. 9 mm
camera end that
In my experience, a cracked or broken probe insert is the commonest cause of
probe tuning changes. A useful tool for checking on the condition of the inserts
and coils is a borescope/endoscope camera. I have one with a 3.9 mm camera end
that can go directly into a 5 mm probe, or if desired, go into a 5 mm NMR tube if
you are concerned about scratching the inserts with the camera end itself. These
cameras are readily available for under $100. They are also useful for checking
if sudden shim changes are resulting from someone breaking a sample inside the
probe, and not thinking that is important enough to mention to staff.
Two caveats with these inexpensive cameras:
-the business ends are ferromagnetic, making them not suitable for checking
out a probe while it is inside the magnet.
-labeling this product as an endoscope seems to endorse DIY internal medicine.
This may not be a good idea. At the least, they are inexpensive enough that it
would not be necessary to use the same camera for NMR probes, and non-NMR
applications.
Sending the probe back to the vendor's probe shop is by far the best way to
get it back to like new condition, regardless of the cause. (I was very sorry
to hear that JS Research had exited the probe repair business, as I got
several top notch repairs done through them.) At least some Bruker room
temperature probes have free standing coils that are not held to the insert
by adhesive, such that the insert can potentially be repaired in the field.
I did that a number of times in my old job, but have not had any broken inserts
on Bruker probes in my current job. I have had several broken Varian probes,
where the coils are glued on to the inserts, and I don't feel at all confident
that I could repair those anywhere near well enough to make the lineshape spec.
Nearly all of my broken Varian probes have been on instruments that do not have
sample changers. All of my current Bruker spectrometers have sample changers.
I don't think I have enough incidents to make for objectively reliable statistics,
but my definite impression is that sample changers handle tubes more safely than
the rotating crew of grad students and postdocs.
________________________________
From: main_at_ammrl.groups.io <main_at_ammrl.groups.io> on behalf of PLscientific<pavel_at_plscientific.se>
Sent: Wednesday, August 2, 2023 7:20 AM
To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
Subject: Re: [AMMRL] tuning range shifts on BBFO probe
Hi Zdenek,
I would bid on the aging of some of the plate capacitors embedded in RF coil
construction or chip capacitor in the RF circuit. The cleaning of RF coil
may help in the first case, but usually, it is good to take off the gradient
coil for that and it is not that straightforward (wiring can be broken and etc.)
Once, I observed the magic that the tuning range rolled back after a while,
so one more iteration in adjusting the frequency was needed.
Much less probable the tuning capacitor is getting stuck so the range is
restricted. In that case, the ATMA may complain with the error "motor ..
can not be set to the position .... or so."
--
Regards,
Dr. Pavel Yushmanov,
+46736220672
P&L Scientific Instrument Services
Applied Physical Chemistry, KTH
Teknikringen 36,
100 44 Stockholm
Sweden
pavel_at_plscientific.se
http://www.plscientific.se
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Received on Wed Aug 02 2023 - 16:10:56 MST