The question is posed to ammrl but involves mass specs as well ---
since I'm heavily into both areas I should make another point. You
talk about the nmr machines with large magnets -- you did not
identify the mass spectrometers. Yes Quadrupoles and ion traps don't
have magnetic fields but they do have rf circuitry which if not
properly maintained can be leaky. TOF machines have high voltage
pulses and pulsed laser discharges, all of which can create
electrical and rf interference if the frequencies happen to match.
then there are the ICP/ms systems --- they use large horizontal bore
supercon magnets -- the orientation will presumably affect the
direction of higher fringe fields. both disciplines have to work
together. If they are new machines you have one set of problems - if
older machines shielding may be poorer or affect of outside fields
(magnetic or rf) may be greater. ICPMS and especially sector MS
instruments will create the biggest problems for the nmrs but what
will the nmrs do to the mass specs.
remember that rf can create overtones --- everything is fine when you
measure an instrument for leakage at its designed frequency but
higher overtones may be a serious rf leak and not shielded since
nobody thought to look for them. We once had a piece of equipment
transmitting on its 22nd harmonic that wiped out the local ambulance
dispatcher's frequency.
jack
--
Prof. Jack M. Miller,
Associate Vice-President, Research and
Dean of Graduate Studies,
Professor of Chemistry,
Brock University,
St. Catharines, Ont.,
Canada, L2S 3A1.
Phone (905) 688 5550, ext 3789
FAX (905) 684 2277
e-mail jmiller_at_brocku.ca
http://chemiris.labs.brocku.ca/~chemweb/faculty/miller/
Received on Wed Feb 27 2002 - 12:47:12 MST