Some time ago we measured the T1 values for water protons in H2O at low
field and found reasonably long values - even when fully areated. However
measuring the T1 at 500 MHz (and fully areated) for the combined proton
peak of Ethanol (OH) and H2O with a mixture of 70 % ethanol (volume) and 30
% distilled water - T1 values of 20 -30 ms was found - which I find
somewhat short.
(The lock was disabled and the receiver gain reduced to a minimum and the
shim values from a sample with a small amount of D2O instead of H2O was
used.)
We used the standard pulse program "t1ir" - first with very long delays
and later with shorter delays after the initial "sreening" showed short
values. In my ignorance I belived that the field strength should not
matter much?
The nmr tubes were new and were washed thorougly with the solution to be
investigated (5 times), but not cleaned in any other special way.
Any known paramagnetic impurities in new nmr tubes?
Doing a fairly extensive search on CAS I did not come up with literature
values for T1 for EtOH/water samples. Has anyone done something similar?
Or having an explantion for the short values?
Thanks for any response
Frode Rise
----------------------------------------------------
Dr. Frode Rise
Department of Chemistry
University of Oslo
P.O. Box 1033 Blindern
N-0315 Oslo
Norway
Voice: (+) 47 224 60741, (+) 47 224 61476, (+) 47 228 55514
Fax: (+) 47 228 55507
http://www.uio.no/~froderi/
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