ammrlers,
I received a number of replies to my query about silicon-free NMR tubes:
1) Use a sweepwidth that excludes the glass signal. (These samples
have resonances quite near the glass peak.)
2) Use a long pre-acquisition delay to get rid of some/much of the broad
glass signal. (These samples have broad resonances as well.)
3) Don't worry about the NMR tube until checking the background from the
glass inserts in the probe itself. (These are strong enough to swamp my
sample peaks.)
The results of (3) enabled me to convince the student that solid-state
was the way to go. (I suggested it initially, but she wanted to do
solution if possible.) So, I did not persue the tube issue further.
Listed here are other suggestions:
4) Norell might have PTFE tubes or inserts that could be used as a
tube. (I didn't check.)
5) New Era (
http://www.newera-nmr.com ) has a teflon-glass hybrid.(I
couldn't find it on the web page.)
6) Alumina from Wilmad (
http://www.wilmad.com) (I couldn't find this
on their web either, but Wilmad does have a nice technical article
http://www.wilmad.com/NMR012.html )
7) Make a hybrid tube with a glass top and a teflon bottom.
8) Use PTFE tube liners shimmed with a little electrical tape to fit
the spinner. You cannot spin these since they are not very straight.
These can damage your insert if they get too crooked. They can be
straightened by putting them inside a glass NMR tube, heating them in an
oven, then letting them cool while still in the glass tube.
9) If you are going to use a relaxation agent in your solution you can
get by with high grade crystalline quartz tubes (Suprasil(R)). Take a
few dummy scans to saturate the Si in the tube and you will never see it
again (assuming repetition rates on the order of 1-5 seconds).
10. Shigimi (
http://www.geocities.com/~shigemi/page9.html ) has a
silica/alumina hybrid tube.
11. Saphikon (
http://www.saphikon.com) makes sapphire (alumina with
impurities) but I didn't find NMR tubes on their website.
thanks for all the suggestions,
kas
--
Karen Ann Smith karenann_at_unm.edu
Manager, NMR Facility Adj. Asst. Prof.
Dept. of Chemistry Clark Hall
University of New Mexico Albuquerque, NM 87131
505.277.4031 url: http://www.unm.edu/~karenann
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Received on Wed Sep 06 2000 - 11:55:44 MST