Thanks, Geoff.
It was not my proudest moment of being the receiving end of the 4JFF gotchas.
Thanks a lot for pointing me to this paper!
Paris
> From: main_at_ammrl.groups.io On Behalf Of Akien, Geoffrey via groups.io
> Sent: Wednesday, July 29, 2026 10:22 AM
> To: main_at_ammrl.groups.io
> Subject: Re: [AMMRL] 19F-19F COSY Exepriments
Hi Paris,
If you weren't already aware of it here is a good overview on 2D 19F experiments:
https://www.sciencedirect.com/science/article/abs/pii/S0079656505000646
It has good coverage of the 4JFF gotchas in perfluorinated molecules and why
the COSY in particular isn't as intuitive to use compared to the more typical
1H context.
Thanks
Geoff
________________________________
> From: main_at_ammrl.groups.io on behalf of Paris Ning, PhD via groups.io
> Sent: 29 July 2026 13:17
> To: main_at_ammrl.groups.io
> Subject: [External] Re: [AMMRL] 19F-19F COSY Exepriments
Hi Clemens,
Thanks a lot! I’ll adjust my exp parameters as you suggest and try it again.
I found that one of the reasons I thought my COSY was “weird”
was that there seemed to be some conflicts on the assignment of the PFOA molecule –
a few papers did 1D assignments, which were my main reference point, did not
agree with other papers with assignments from COSY and NOESY. The discrepancy
seems to arise from 4J and 3J F-F couplings. Although the current data is still
not perfect but that finding makes the spectrum more reasonable. I’ll see
what I can get with the new experiments.
Thanks!
Cheers,
Paris
> From: main_at_ammrl.groups.io On Behalf Of Anklin, Clemens via groups.io
> Sent: Wednesday, July 22, 2026 9:41 PM
> To: main_at_ammrl.groups.io<mailto:main_at_ammrl.groups.io>
> Subject: Re: [AMMRL] 19F-19F COSY Exepriments
Hi Paris
the trick with 19F COSY experiments is having a long enough evolution time
in t1 to allow the magnetization to fully evolve. with 3J F,F couplings in
the range of 10 Hz you would get maximum transfer at ca 50 msec. So the COSY LR
help in building signal intensity. The next issue is that you have a very wide
sweep width and some small couplings. You need to acquire with sufficient
resolution in f2 to somwhat adequately digitze the signals. I would set TD
in F2 to 8K or larger. and TD in F1 to 256 or 512.
This should in principle give you a decent COSY.
Clemens
On 7/22/2026 2:17 PM, Paris Ning, PhD via groups.io wrote:
Hi everyone,
I have been trying to set up a 19F COSY experiment that can be used routinely
reliably. I am using PFOA as the model molecule and we have a Bruker system.
I've tried a few pulse sequences but none gave good results:
- COSY with gradient pulse for selection and purge pulse before d1 (cosygpppqf)
- COSY with delay for longrange coupling (cosylrqf) - tried with various delay values from 0.1 ms to 50 ms
- Vanilla COSY
Wondering if anyone has a better COSY pulse sequence or another type of cor=
relation experiments to recommend.
Thanks a bunch!
Cheers,
Paris
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Received on Wed Jul 29 2026 - 07:51:05 MST