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Hi everyone, Has someone tried to run proton decoupled of 14N? How long should be the 14N decoupling pulse? I had some problems with the lock signal (lost it) when I tried the pulse sequence zgig (1H on the observed channel). When recording 1D 14N spectrum, the lock was fine (it had some small distortions, but was not lost). We have a DRX 400 MHz spectrometer, with Topspin 1.3 and a BBFO atma probe. Any suggestions on how to set up this experiment will be highly appreciated. Thanks a lot, alina |
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Normally, unless in a highly symmetric environment such as NH4+, the relaxation properties of 14N are such that there is no visible coupling to attached protons, so proton decoupling is not needed in 14N NMR. If you do see multiplet(s) you could use the same conditions as you would use for 13C and it will be fine. You could move the proton offset to the NH/NH2 region in the 1H spectrum, although this should not be necessary. Thank you for your answer. But I think you are referring to 14N with proton decoupling. I need to run the experiment the other way around-1H with 14N decoupling. What I don’t understand is the lost of the lock signal when I try to run the ZGIG pulse program, with 1H observe and 14N decoupling. - alina (Aug 08 '13 at 09:02) |
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The 14N decoupling is getting through to the 2H channel. It may be a problem of filtering. Use a 2H filter, if one is available, between the probe and the 2H preamp. When you insert (or change) the 2H filter, the lock phase will have to be re-adjusted. Another possibility is probe arcing during the 14N decoupling pulse, which may interfere with the 2H channel. I don't think that is likely, but if it occurs, the indication for troubleshooting would be high reflected power on the power amp assigned to the 14N channel. |
