Greetings all,
I'm having a little trouble with 11B NMR. We have a Varian INOVA 500
system and I'm currently using a 10mm BB probe. Our sample of interest has
low levels of Boron (1-50ppm per species, using 1ml of Benzene-d6/3ml of
sample). I have been tuning the probe for each sample as it seems the
sample-to-sample variation is quite significant. The Boron species in the
sample are sensitive to the matrix (we do know that benzene does not
affect them). So, we've been using an external reference of 1 v%
BF3(Etherate) in benzene in a 5mm insert. We used the 1 v% BF3(etherate)
standard to optimize the pulse width for a full 90deg pulse (our samples
are too dilute to do any pw90 experiments). We are trying to optimize
acquisition time (at) and the delay (d1). Currently we've been varying the
at between 0.05 and 0.2 seconds with a delay anywhere from 0-0.3 seconds.
We are decoupling proton, but we've been unable to run a gamah2 on these
samples.
Our results are hit and miss, resolution pretty low. We've tried running
the sample w/o dilution, but we sacrifice lock. I'm not sure what else to
try. I even tried giving the magnet a Valentine's Day gift, but that
didn't seem to help either. Do our above parameters seem to be in the
ballpark for 11B NMR? Does anyone have any tips for running 11B NMR and/or
experience with low levels of Boron? Any help would be greatly
appreciated.
Jim Simpson
Invista
Orange, TX
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Received on Fri Mar 04 2005 - 14:03:49 MST