Decoupling-problem
Ingmar Sethson (ingmar@indra.chem.umu.se)
Wed, 12 Apr 95 08:00:55 +0200
Dear netters,
We have experienced a problem when we try to do proton-decoupling on Phosph.
NMR. When we use waltz16 or garp-decoupling we can observe artefacts in the
spectra as manifested by side-bands (spaced by roughly 200 Hz). These side-
bands do not occur when we use BB-decoupling. We don't want to use BB since
on this old probe (10mm BB X-probe) we have to use 7dB on the proton channel
to decouple the coupling (in this case 570 Hz) and the sample starts to
heat. Also, when we use a 90-degree dec-pulse of 100 us in the comp. dec.
schemes the sidebands are not that intense but if we lower the power (90
deg pulse of 200 us) the sidebands really get intense (almost as the same
magnitude as the signal).
For your information: we have a 500 AMX2-spectrometer, the proton dec. freq.
is set on resonance.
Has anyone else encountered this problem with composite decoupling on
phosphourus ? All suggestions, exlplanations and ideas are welcomed.
ingmar
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* Ingmar Sethson *
* Dep. Org. Chem., *
* Umea University *
* S-901 87 UMEA, Sweden *
* Ph.nr. : +46-90-16 62 86 *
* Fax.nr. : +46-90-13 88 85 *
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