nmr sample volume
=?ISO-2022-JP?B?GyRCOWI2NkAsOzAbKEI=?= (t_seizo@jwu.ac.jp)
Fri, 6 Nov 98 13:18:17 +0900
I am somewhat different. We use 400 MHz wide bore magnet and our
frequent users are undergraduate students of Organic Chemistry. They are
recommended to use low cost tubes (300 yen) of Shigemi Co. Ltd. I don't
find an appreciable difference for most samples in the spectral
resolution, comparing with the most expensive ones except for the
sensitivity due to wall thickness. Spinning side bands are mostly
determined by shimming and spinner, at least in our case.
As for sample volume, I believe 3 times of the coil length is best for
most users who touch only Z and Z2 gradients. My lab uses 2 times of the
coil length to save samples, where they need to adjust Z3 gradient and
sometimes Z4 from standard shim file.
I don't know if it is characteristic to our wide bore magnet or not,
but the spectral resolution does not make much change in aqueous samples
between spinning and without spinning, when it is fully shimmed. Without
spinning, even smaller volume can be used to gain more sensitivity, which
is worth for the time of shimming. Of course, I use the Shigemi
microcell for most demanding sample of limited volume. It is recommended
to use 250 uL but I often use 100 uL for 5mm tube without trouble.
>Date: Thu, 5 Nov 1998 11:02:57 -0400
>To: ammrl <ammrl@wwitch.unl.edu>
>From: Sandip Sur <sur@chem.rochester.edu>
>Subject: nmr sample volume
>
>Dear AMMRL members:
>
>I have been thinking to standarize sample volume/height and tube quality
>for routine and not-so-experienced nmr users in our department. I am sure
>these and similar nmr management issues were discussed before, but I want
>to receive some feedback from your own experiences.
> It is difficult to judge the quality of each nmr tube by routine
>student users, and I recommend using at least Wilmad 528-pp at 400 MHz or
>even at 300 MHz. The sample height for high resolution nmr in a 5 mm tube
>should be about 5 cm high. I have seen recommendation of 4 cm sample
>height, too. For expensive solvents, smaller sample height is, however,
>desirable.
>
>Thanks in advance for your comments,
>
>Sandip
>
Seizo Takahashi
Dept. Chem. & Biol. Sci.
Fac. Science
Japan Women's University