Hi Purush,
While zgbs will indeed do a reasonable job of background suppression, the
useable bandwidth is very poor because this relies on hard 180 pulses, so isn’t
a good choice for most 19F applications. cpmg1d has similar bandwidth limitations,
and you would also get J-modulation if you have F-F J-couplings to deal with.
The aring*sp* sequences make use of adiabatic shapes to cover the range of
interest, but since the only available options (3.6.1 and newer) are aringpgsp
and aringpgsp30, you’d have to modify them yourself if you don’t
need the decoupling on F2.
On TopSpin 3 you can either modify your 19F prosol entries to calculate the
required power levels for those shapes you, or more conveniently, use WaveMaker.
On TopSpin 4 the prosol entries are already there so you don’t need to
use WaveMaker, but its still there if you want to make adjustments to the shape –
you may find you can get small improvements over the defaults by changing the
pulse length or frequency sweep.
You are unlikely to get perfectly flat baselines using the “right”
pulse sequence alone, but it will certainly make it much easier to use post-processing
methods to get there.
As others have suggested, the “traditional” way to clean up
the baseline using post-processing was to use backwards linear prediction
and this works just fine, but there may be some fiddling involved while you
figure out what a reasonable TDoff is to use for your acquisition parameters.
The AU programs c13cryo and cryoproc1d might be worth looking at.
The “new” way of handling this in TopSpin is to let apbk handle
all of this for you (3.6.3ish and 4.1.3,
https://www.bruker.com/content/dam/bruker/int/en/resources/bbio/magnetic-resonance/application-notes/T186209_Bruker*20Whitepaper*20Deep*20Learning*20in*20NMR.pdf
and it usually does a pretty good job without needing to adjust any parameters, and
not needing to modify the initial FID either. If you have access to Mnova, then
this has a wide range of baseline correction routines including apbk.
For the flattest baselines you will probably need to use a combination of pre-
and post-processing methods, and some trial and error for your specific probe.
All of the background suppression methods will also suppress intrinsically
broad peaks, so depending on your application there may be limits on what you
can achieve.
Thanks
Geoff
> From: main_at_ammrl.groups.io On Behalf Of Ulrike Werner-Zwanziger via groups.io
> Sent: 10 May 2026 14:22
> To: main_at_ammrl.groups.io
> Subject: [External] Re: [AMMRL] 19F peaks issue
Hello,
in ssNMR, a good suppression of background signals can often be accomplished
with Hahn echoes since the background has different 90 degree times for agiven power.
Happy resonating,
Ulli
On Sun, May 10, 2026 at 10:18 AM David Rovnyak via groups.io wrote:
Signals of interest often lie in this regime so it has to be dealt with to
see those clearly. Unless a special probe is constructed with lower background,
this background can be quite large in typical probes. One option is that if
your native signals are narrow, then a modest amount of back lp can get rid of
most/all of this background without harming your native lines.
-DSR
On Sat, May 9, 2026 at 6:56 PM Eugenio Alvarado via groups.io wrote:
You can use backward linear prediction to get rid of it. It is likely background
from the probe.
Eugenio Alvarado
Director, NMR Lab. Room 3500
Chemistry Department, University of Michigan
930 N. University Ave., Ann Arbor, MI 48109-1055
Voice: (734)-764-9924
On Sat, May 9, 2026, 5:37 PM Karel Klika via groups.io wrote:
Hi Puresh,
This is just background from the probe, I get the same on my Prodigy (I checked
it as it is different to my rt probe). So obviously you have tuned and matched
and have a pulse with some power but there is no flourine in your sample.
Sincerely,
K. Klika
________________________________________
> From: main_at_ammrl.groups.io on behalf of pothula purushotham reddy via groups.io
> Sent: 08 May 2026 23:59:10
> To: main_at_ammrl.groups.io<mailto:main_at_ammrl.groups.io>
> Subject: [AMMRL] 19F peaks issue
Hi there,
I am measuring ¹⁹F NMR on a Prodigy probe at 400 MHz, but the
spectra look strange/weird. Does anyone know what might be causing this or
how to fix it? Any suggestions would be greatly appreciated.
Thank you!
Best
Purush
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