Date: Thu, 7 Jan 2021 13:08:27 +0000
Dear ammrlers,
A happy new year to everybody and special thanks to all of you who took the
time to answer my question about 19F decoupling.
Please find below all the suggested solutions that I have received.
We have tested the one suggested by Bruker (bi_p5m4sp.2 in answer 1)) and it
works wonderfully. In Topspin 4 everything is in edprosol, so "getprosol" just
sets it for you.
Thanks again. Stay safe,
Gabriel
[Descripción: logoICIQ]
Dr. Gabriel González Ferrer
Responsable RMN / NMR Manager
Institut Català d'Investigació Química (ICIQ) /
Institute of Chemical Research of Catalonia (ICIQ)
The Barcelona Institute of Science and Technology
Av. Països Catalans 16 - 43007 Tarragona (Spain)
Phone +34 977920207 / +34 686669420 - Fax +34 977920224
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Dear all,
Does anybody know of a good, and easy to implement, adiabatic decoupling sequence
for fluorine decoupling in Bruker Topspin?
For the moment we are using garp4 (CPDPRG = garp4), with the obvious spectral
window limitations. So, if somebody knows of a better sequence available in
the Bruker library, it would very much apreciated.
Thank you very much. Best wishes for the holiday season. Stay safe.
Dr. Gabriel González Ferrer
Responsable RMN / NMR Manager
Institut Català d'Investigació Química (ICIQ) /
Institute of Chemical Research of Catalonia (ICIQ)
Av. Països Catalans 16 - 43007 Tarragona (Spain)
Phone +34 977920207 / +34 686669420 - Fax +34 977920224
ggonzalez_at_iciq.es<mailto:ggonzalez_at_iciq.es> - www.iciq.es<http://www.iciq.es/>
1)
Dear Gabriel,
We have new adiabatic shapes in our release for use in Fluorine decoupling.
So you should use the normal cpd-program (as for carbon) bi_p5m4sp_4sp.2 and
as shapes use Crp120,1.5,30.4 and Crp120,0.75,30.4, again similar to adiabatic
decoupling in carbon. This will cover about 100 kHz decoupling bandwidth.
2)
Hi Gabriel,
We have a similar challenge here and I have not yet found an acceptable solution.
Two years ago I did try "BUSS" decoupling and was able to increase the effective
decoupling bandwidth from 20 kHz (GARP, 60 us) to 44 kHz, but the signal-to-noise
was ~15% lower with BUSS than with GARP.
I briefly attempted Crp42-based decoupling with a P5M4 cycle but could not
obtain an improved result compared to GARP. Certainly I am no expert in this
area and it would not surprise me to hear that others have had success. One
problem I ran into was that our console did not like using a shaped decoupling
pulse for a long AQ (I believe it does not have enough memory).
I would be grateful to know if you hear of any successes in this area, as our
researchers request a 19F-decoupling 13C from time to time!
3)
Hello Gabriel,
Yes, there is a very good pulse program you can use for broadband adiabatic
decoupling.
I have used: bi_p5m4sp_4sp.2
If your prosol table has been setup properly, then it should already be populated
with the appropriate adiabatic chirp pulses.
I use at 1.5 ms Crp120,1.5,30.4 pulse for the main part of the decoupling sequence.
For the bilevel part of the decoupling I use: Crp120,0.75,30.4
I hope this helps.
4)
Hi Gabriel,
It's more a question of TopSpin not having the right shaped pulses configured by
default, then a matter of pulse sequence.
You can use CPDPRG bi_p5m4sp_4sp.2 for bi-lev adiabatic decoupling, but you
need to generate the right shapes yourself.
You can edit your 19F prosol entries shaped pulses #12 and #13, and replace
with something more sensible you've made in ShapeTool.
Alternatively, you can use WaveMaker to generate the two shapes for you e.g. if
you have TopSpin 3.6 you can do:
USERA1 sp31(p63):wvm:bilev_1:f2 sm_chirp(112.5 kHz, 5 ms; Q=3) ss=2us
USERA2 sp14(p):wvm:bilev_2:f2 sm_chirp(112.5 kHz, 2.5 ms; Q=3) ss=2us
(the last one intentionally doesn't have an assigned pulse length because of the way the CPDPRG works)
Then type wvm -a to generate the shapes.
5)
Hi Gabriel,
for decoupling over a large freuqncy band (such as 13C on a 900 MHz spectrometer)
we are using the BUSS sequence developed by the Glaser group a few years ago.
As far as I know, the sequence is not yet part of the Bruker library, but you can
download the shape e.g. from here http://wiki.g-nmr.de/pp/ (the original literature
literature is also cited there).
the decoupling consists just of repeating this shape, so the "cpd program" would look like
/1 pcpd:sp18//
//jump to 1/
and the decoupling power needs to be calibrated to 14.7 kHz (= ca. 17 us
for a 90° pulse). Don't worry, that's only the PEAK power, the average
decoupling power is merely 4.4 kHz. The duration of the shape (pulse length.
e.g. pcpd2,) needs to be set to 123.2 ms.
This decoupling sequence has been optimized for 1H,13C coupling up to 150 Hz,
so it should be more than adequate for the usual 1H,19F coullings (which
rarely exceed ca. 50 Hz). I made a few tests and found out that the calibration
of the 14.7 kHz is not very critical, so don't worry about this.
6)
It may not yet be in the Bruker Library, but you may wish to look at work by the
Manchester group of Gareth Morris:
"Increasing the quantitative bandwidth of NMR measurements", J. E. Power,et al
pdf below.
Please let me know if it works.
(image/jpeg attachment: image001.jpg)