Thanks for the large number of replies.
Firstly, I maybe gave the wrong impression that the probe was going to
be used for routine work. We already have a QNP probe for routine work.
As many of you guessed we are over our quota of natural product chemists
here (or "bush boilers" as we prefer to call them). They have their new
600 MHz machine (with cryoprobe) to work with. So this probe will be
mainly used for phys. chem.. and inorganic work as such I have been
swaying towards the larger size probe. I will skew my summary in an
attempt to justify 10 mm probes even though many respondents "would not
use a 10mm probe if they had one".
I've had 23 replies. Many thought the larger sizes were obsolete due to
the increased sensitivity of modern instruments.
One reply suggested that 5 mm was a bit big!
I had only two replies in favour of the larger probe size. The larger
probes can be useful in the following cases;
1) lots of sample, but poor solubility (typical of polymers);
2) when doing quantitative measurements;
3) low gamma nuclei.
Also you can use a 5mm tube in a 10 mm probe - with poor filling factor
(I didn't know this)
The arguments for 5 mm probes.
1) Less solvent (but of course you could go for undeuterated/unlocked)
2) Often the sample is of limited size.
3) Shimming was thought to be easier for a smaller probe.
4) Manufactures concentrate on 5mm probe sizes so maybe the larger sizes
are not of optimal design.
There also seems to be reluctance to change probes. I feel that a probe
that does everything will not be optimized for anything and anyway
changing probes makes me feel like a real spectroscopist. I'm off to do
some 27Al and 14N (wish I had a 10 mm probe!)
David Stephenson
Chemistry Department
University Of the West Indies
St. Augustine
Trinidad and Tobago
West Indies
Received on Tue Sep 02 2008 - 06:58:02 MST