While performing DOSY, I noticed something strange that I can't explain:
I performed 2 DOSYs of 2 polymers with exactly the same parameters (pulse sequence, small and big delta, temperature, same solvent (CDCl3)). What puzzles me is that the diffusion coefficient for the residual CHCl3 in the 2D DOSY plots of Mestre (same processing) is extremely different in both spectra (1.6e-04 and 5.4e-05). I am not very experienced with DOSY, but shouldn't these Ds for CHCl3 at least be in the same range?
I am not concerned with finding exact and correct diffusion coefficients, but rather performing mixture analysis, yet this result seems strange and makes the impression that the processing is not very reliable.
Hallo,
It's not a big difference if the polymers are different or the concentration is different. What is the standard deviation of these coefficients you mention? The polymer signals may have a good decay and with enough increments for the fitting, this may not be the case for CDCl3. Do you have a good decay for the CDCl3 signal?
You could repeat the experiments with the shortest possible d20, the diffusion coefficient of the components in the sample should be "equal" to your first measurement.
If you are using an edited pulse sequence, mestrenova will not be able to calculate the diffusion time (big delta) properly and this results in an error.
Any difficulty look for our group in Regensburg, we can help.
- Badges
- Science topic
- Similar topics
- Correction