Saturday, July 04, 2009


Carlos kindly gave me a copy of the DOSY spectrum he showed on his blog last year.
I am experimenting alternative processing routes. Here is a detail of the caffeine peaks, after applying the rudest (and probably simplest) treatment. The decays have been linearized (by taking the logarithm). The slope of the line is proportional to the diffusion coefficient. The final results are reported as a normal DOSY spectrum.
Click on the thumbnail to see the image at natural scale.

There is less signal/noise in the tails of the peaks, obviously, therefore the error increases: graphically we see the wings of a butterfly.
Being that it's impossible to correct the phase perfectly, some butterflies are asymmetric.


At 3:30 PM, Anonymous Jean-Marc Nuzillard said...

There is a time for graphical arts and a time for diffusometry, even though the two fields may sometimes collide, as you remarkably proved in your post.

I admit that the classical 2D DOSY display is very helpful to show how individual subspectra of mixture components may be extracted from a mixture spectrum.

The example that is provided by Carlos in his blog
would benefit from a processing trick I use when there is no multiplet superimposition:
I simply integrate the multiplets that are recorded at different gradient intensities and I perform a monoexponential fit on integral values.
I suspect the noise on integral values is lower than the one in individual columns of the 1D spectra set, thus making D values
more accurate.
Bye bye butterflies.
This idea is absolutely trivial
but maybe it would be interesting
to implement it.


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