Dear Carl,
If the signal in question is coupled to only one other signal which is
decoupled than a singlet will be observed and residual signals may be C-13
side bands or spinning side bands (try the experiment non-spinning). If the
signal in question has coupling to more than one other spin than those
couplings will still exist and the multiplet is only simplified.
On an older Bruker system, it may be possible to increase the width of the
spectrum affected by having a list of closely spaced frequencies to which
the decoupler is applied in succession and cycled during the experiment. It
is also possible to switch the power setting between acquisitions for
multipeak decoupling. Also sometimes what you may set as the middle of a
multiplet may not be the middle in practice and a slight variation to one
side of this frequency produces better results. Increasing decoupler power
will spread the frequency a little. I'm sure a Varian user can help you with
the specific pulse sequence set-up.
Hope this helps.
Mo
-----Original Message-----
From: Bachmann, Carl [mailto:cbachm_at_biochem.swmed.edu]
Sent: 12 January 2000 17:16
To: AMMRL
Subject: homonuclear decoupling
Dear AMMRL's:
A prof in my department has asked me this question several
time -- Obviously I haven't been able to answer it satisfactorily.
I hope you can help.
Re a homonuclear decoupling experiment-- decoupling is
incomplete as judged by residual peaks adjacent to say
the major collapsed singlet. He insists that on a Bruker
250 that we used to have he could adjust the width of the
spectrum affected by the decoupler. I understood this was not
decoupler power. Please excuse my ignorance but is
this a sensible assertation? If so, is there anyway to duplicate
this effect on Varian's Inova? I really appreciate
any help/light you might shed on this.
Regards, Carl
--------------------------------end-------------------------
Carl Bachmann, 214-648-6748
cbachm_at_biochem.swmed.edu
Department of Biochemistry
UT Southwestern Medical Center
Dallas, TX 75235
Received on Thu Jan 13 2000 - 09:13:09 MST