During the installation of our new 500 NMR, we noticed that there is a
magnetic field interference at our site. There are magnetic pulses that
lasts about 10 seconds and appears every 45-70 seconds. The strength of the
pulse is about 3-5 m gauss, and the strongest reading is in the NMR room.
One over night monitoring showed that there was not interference from
7:00pm to 7:00am next day.
We had checked around the NMR room, but did not find any source that could
cause this interference. The NMR is at ground floor, there is not any
basement. There are only offices (not even labs) on the floor above NMR
lab. There are mechanical rooms near by (30-50 feet away), but the readings
in those rooms were much weaker than in NMR room. We tested equipment in
those mechanical rooms (air handling fans) by turning them off, the
interference was still there. We do have mass spectrometers in the same
building, but they are on the third floor of another wing (more than 200
feet away, at least).
We would like to have suggestions from AMMRLers, what could cause this
interference, how can we solve this problem on the NMR side if we can not
identify the source, or we can not do anything about the source if we find
it. Now, we see lock fluctuating and t1 noise all over the 2D NOESY, and
spectra obtained without lock are useless.
Thank you for your help!
Donghui Wu
Colgate-Palmolive Company
732-878-6189