Many thanks to all who replied to my request on whether low quality sample
tubes could damage NMR probes. I received over thirty replies, some quite
detailed!
The responses were pretty well evenly divided. About half are using these
"thrift" or "throw-away" tubes with few or no problems. The other half had
probe damage that was at least suspected to be due the use of these tubes.
One possible reason is the wide variety of tubes in this category: from relatively
decent to total crap. (Can I say "crap" on this group, Rich? :-) )
Most have found that these tubes produce spectra that are inferior to spectra from
the better tubes. For some purposes, this may be acceptable. The low price
tubes were generally found to be more difficult to shim.
Many or most recommended NOT spinning these tubes.
Placing of even good quality sample tubes into a drying oven was cited as a recipe for
probe disaster.
Several legitimate reasons for using disposable NMR tubes were cited. These include:
- High volume operation with sample changers.
- Fear of sample cross-contamination, especially in a GMP/GLP environment.
- Difficult to clean samples, such as polymers.
My concern with tubes that are significantly under-sized, is with spinner turbines that
grip the tube with fingers or an "O" ring only at the top. This allows considerable
movement or slop at the bottom of the turbine, possible allowing the tube to strike the
probe insert. Spinner turbines that have fingers or "O" rings at both top and bottom
should hold the straighter and be less of a problem in this regard.
Because of the large number of replies rather than posting them all here I will paste them
together and place them on our web site:
http://www.umanitoba.ca/chemistry/nmr/nmrsource2.html
(As the post office says: "allow a few days for delivery")
Cheers, and thanks!
-Kirk
Kirk Marat, Ph. D., NMR Facility Manager
Dept. of Chemistry
University of Manitoba
Winnipeg, MB, R3T 2N2, CANADA
ph. (204) 474-6259 FAX: (204) 474-7608
kirk_marat_at_umanitoba.ca
ALL SPAM forwarded to Spam Cop
Received on Tue Jun 07 2005 - 19:44:39 MST