> > 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.
>
> Make an image (a 1D projection if you only have one gradient). Put some
> object of known dimensions into the tube with water. Acquire the signal
> with the gradient on. Measure the distance between two identifiable points
> of known physical distance.
>
I have used two samples for this purpose. One is a 5 mm tube with a 4 mm teflon
plug (with a tiny hole to the pressure out, otherwise snug fit at room
temperature); the other with a 2 mm plug. Both contains H2O/D2O (saline). The
little plug (placed in the center of the receiver coil) is for large gradients
(100-200 Gauss/cm); the larger one for smaller gradients (<50 Gauss/cm). When
data is acquired, I normally take the absolute value of the spectrum to get a
nicer picture. Just measure the width of the frequency "hole" and use it in the
equation. You also get an idea of the height of the receiver coil from the outer
edges.
Good luck!
73, Peter
@ @
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| Peter Lundberg Ph: (+46 90) 16 59 73 |
| Physical Chemistry Fax: (+46 90) 16 77 79 |
| U of Umea Email: PeterL@chem.umu.se |
| S-901 87 Umea Efax: PeterLundberg@f090167779.fax.sunet.se |
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