Currently we are setting up a Bruker DRX300 for diffusion measurements using
the sequence by Alteiri etal (JACS 1995, 117, 7566). Calibration of the
gradient strength gives a us a strange error. We calibrate the gradient in
two ways: first we determine the modulation of the residual proton signal in
D2O (known diffusion constant of 1.9*10-9 m2/s, Price Conc. Mag. Res 1998,
10, 197) with varying gradient strength, this results in a gradient strength
of 26 G/cm at 100% (3ms gradient from 5% to 60%, 100ms diffusion delay,
factor 20 signal modulation). Shape analysis of the one dimensional image of
a 90%H2O/10%D2O sample results in a gradient strength of 52 G/cm (1% and 2%
gradient strength we use two vortex plugs in the tube as we don't have
shigemi tubes). The specifications for the gradient amplifier and probe
(single axis Z-gradient) are max 50G/cm so the second experiment seems to
give the right value.
Any help is appreciated, if a summary of the reactions is desired I will
post one.
sorry for cross posting.
Sincerely,
Sander Gaemers
IMC, University of Amsterdam
Nieuwe Achtergracht 166
1018 WV Amsterdam
Tel (31)-(0)20-5256460
Fax (31)-(0)20-5256456
e-mail Sander@anorg.chem.uva.nl