NMR EPS-2: URL, Correction
roy hoffman (roy@cc.huji.ac.il)
Mon, 11 Mar 1996 16:11:36 +0200 (GMT+0200)
7th March 1996
Dear AMMRL members,
We are trying to measure diffusion rates of small to medium sized molecules
in solution (D2O, THF-d8, and methanol-d4). We are using the STE pulse sequence
and incrementing the gradient strength. This should yield a Gaussian intensity
curve for each signal. However, we often get non-Gaussian forms and results that
vary from one day to the next. I believe that the problem is convection as it
is much weaker for more viscous solutions such as D2O than others such as
MeOH and is weaker in narrower tubes (we have tried internal diameters down to
1.7 mm). I have two questions.
1) Does anyone know how to further reduce the effects of convection
2) Is there any way of making an absolute callibration of the gradient
strength without relying on a known diffusion constant as I am getting
suspicious that some of them may have been corrupted by convection.
Thank you in advance for your help.
Yours,
Roy.
--------------------------------------------------------------------------------
V
I Dr. Roy Hoffman,
I Manager, NMR Laboratory, Department of Organic Chemistry,
A a X The Hebrew University of Jerusalem, Jerusalem, Israel 91904.
XJ lX Tel. (972) 2 6585327, Fax (972) 2 6585345, Email roy@shum.cc.huji.ac.il
X X Web page http://drx.ch.huji.ac.il:8080/hoffman.html
X
--------------------------------------------------------------------------------