Hi Piotr,
Attached is a 71Ga spectrum of 0.5M Ga nitrate that we collected here on
our Bruker 600 w/Prodigy (multinuclear) cryoprobe.
The signal is near 0 ppm. Our referencing is the default set by the
software from the lock resonance. FYI our absolute frequency on the 600
for 71Ga is 182.9890358 vs. 600.0160131 for 1H (locked on D2O). You
should be able to calculate the expected absolute 71Ga frequency on your
system from that.
We collected 1024 scans (d1=0.1 sec, aq=0.1 expt=~4min) and obtained about
a strong spectrum, ~200:1 S/N with lb=100 Hz. With short T1 and T2 of the
quadrupolar nucleus you can collect many scans in a very short time.
While we would expect more sensitivity under our conditions:
1) higher field (600 vs 400)
2) cryoprobe = 3x vs conventional BB probe
3) concentration 0.5M vs 0.3M
you should still be able to see decent signal in not too many scans.
Presumably the pw90 and transmitter power values should lie between what
you use for 31P and 13C.
Another test, to be sure there is nothing else weird on your system when
you tune to odd-ball nuclei is to try 11B, 27Al, or 23N. These have
stronger signals than 71Ga, but also have very short T1 & T2.
It should be a piece of cake!
Good luck!
--Mike
-----------------------------
Michael Strain, PhD
Director, CAMCOR NMR Facility
University of Oregon
Eugene, OR 97403-1253
mstrain_at_uoregon.edu
541-346-4605 office/lab
541-556-4077 mobile
http://nmr.uoregon.edu
LinkedIn.com/in/michael-strain-3a8476119
On Wed, 21 Dec 2016, Dobrowolski, Piotr wrote:
> Hi, I am trying to observe 71Ga signal (JEOL ECS 400), using 0.3M sample of
> gallium nitrate in D2O. It seems that autotuning works and I could expect
> that because 71Ga resonance frequency is somewhere between 13C and 31P -
> nothing "exotic". However, if I try to observe the spectrum, using pw90 and
> transmitter power optimized for 31P, I can see only noise after 512 scans. I
> am moving spectral window of 2000 ppm (or 2 [ppt] as Delta calls it) -
> transmitter offset between - 10 ppt and + 10 ppt with increment of 1 ppt
> but I am not able to see anything looking like a signal. I know I should
> expect rather broad resonance (about 400-500 Hz) but I can see only
> noise....am I missing something? Maybe I should use different method for
> looking for that signal.
> Any suggestions?
> Thank you,
> Piotr
>
>
>
> ____________________________________________________________________________
>
> Piotr Dobrowolski, Ph.D.
>
> Sr. Research Associate – NMR Director
>
> Dept. of Chemistry and Biochemistry
>
> Texas Tech University,
>
> Lubbock, TX 79409,
>
> Chemistry Bldg Room 051
>
> Telephone: (806) 834-7706
>
> Email: piotr.dobrowolski_at_ttu.edu
>
>
>
Received on Thu Dec 22 2016 - 12:31:34 MST