> My supposition is that the stray field from the EPR doesn't make
>much inhomogeneity and the lock takes care of the field shift. No one
>reported having done the test to see if the NMR lines move or the lineshape
>changes when the NMR is unlocked and you run the EPR field up and down. We
>sometimes run unlocked for one reason or another. If anyone has or is
>willing to run such a test, I'd be very interested.
>
>Charlie
To which Dave Scott responded,
>Couldn't resist Charlie's challenge...........
>The center or our ER-200D magnet is 3.9M from the center of
>our 400MHz/52 DRX. Running unlocked and increasing CF on the
>ER-200 (X Band 9GHZ) from 40 to 4540 gauss did increase the
>acetone resonance (10% CHCL3 in d6-acetone) by 0.93Hz.
>Three measurements at each field, bounced the epr twice, 0.12Hz/point.
>An intermediate value (2040 gauss) increased the acetone
>resonance by .33Hz (one measurement).
>Running locked, there was no difference (0Hz) between low
>and high field.
I have also been asked to locate a new DPX-300 magnet within 4-5 meters
of a Varian V-7400 15.5" pole diameter (8400 lbs.) EPR magnet. The EPR
group in our Department frequently runs Q-band EPR spectra, in which, they
sweep the magnetic field from 0-15,000 gauss. I am primarly concerned
about the effect this will have on t1 noise in H1/C13 HMBC and NOESY
spectra, and the cancellation of peaks in NOE difference spectra. The
natural products chemists in our Department often require analyses to be
carried out on samples as small as 1-2 mgs (500-1000 MW range). Does
anyone have any experience in this regard? I would appreciate any
suggestions or comments you might have.
Thanks in advance,
Eugene DeRose
Manager NMR Laboratory
University of Wisconsin-Milwaukee
Dept. of Chemistry
Milwaukee, WI 53211
ederose@csd.uwm.edu
(414) 229-5896