245
(Fig. 8). As the methyl group protons of TMZ demonstrate the
most intense shifting it turns out to be the protons with the stronger interaction.
4 Notes
1. Select a solvent with a high viscosity. More viscous materials will
be less likely to create convection. Use solutions such as DMSO
or D 2 O when possible.
2. The experiment should be run at constant temperature. An
accurate temperature calibration with standards methanol or
glycol is necessary. When NMR diffusion experiments are performed at temperature different from ambient temperature,
temperature gradients due to probe design can cause thermal
convection and therefore significantly affect the signal amplitude. This can skew the diffusion rate constants. The influence
of the convection can be seen in distortions in decay profiles. In
such cases NMR tubes with smaller diameter are preferable
because they impose larger temperature gradient for a convection within the sample.
3. Gas flow should be steady (and higher than standard, i.e.,
525 L/h) during the performance of the experiment to ensure
better dispersion.
4. Use sufficient number of dummy scans.
5. Especially the spinning is recommended for isotropic solution.
Spinning can help stabilize forces that may create the convective
flow. Alternatively, specialized sequences can be used to compensate for the convection influences.
6. If you are a Bruker user you can process the data in two ways,
either by calculating the diffusion coefficient through the spectrum or by using the dynamics subroutine where you get a
report with a diffusion coefficient written.
Acknowledgments
This work has been co-financed by the European Union and Greek
national funds through the program “Support for Researchers
with Emphasis on Young Researchers” (call code: EDBM34, ΚΕ
14995) and under the research title “Preparation and study of
innovative forms of administration of pharmaceutical molecules
targeting at improved pharmacological properties.”
2D DOSY NMR: A Valuable Tool to Confirm the Complexation in Drug Delivery Systems
(Fig. 8). As the methyl group protons of TMZ demonstrate the
most intense shifting it turns out to be the protons with the stronger interaction.
4 Notes
1. Select a solvent with a high viscosity. More viscous materials will
be less likely to create convection. Use solutions such as DMSO
or D 2 O when possible.
2. The experiment should be run at constant temperature. An
accurate temperature calibration with standards methanol or
glycol is necessary. When NMR diffusion experiments are performed at temperature different from ambient temperature,
temperature gradients due to probe design can cause thermal
convection and therefore significantly affect the signal amplitude. This can skew the diffusion rate constants. The influence
of the convection can be seen in distortions in decay profiles. In
such cases NMR tubes with smaller diameter are preferable
because they impose larger temperature gradient for a convection within the sample.
3. Gas flow should be steady (and higher than standard, i.e.,
525 L/h) during the performance of the experiment to ensure
better dispersion.
4. Use sufficient number of dummy scans.
5. Especially the spinning is recommended for isotropic solution.
Spinning can help stabilize forces that may create the convective
flow. Alternatively, specialized sequences can be used to compensate for the convection influences.
6. If you are a Bruker user you can process the data in two ways,
either by calculating the diffusion coefficient through the spectrum or by using the dynamics subroutine where you get a
report with a diffusion coefficient written.
Acknowledgments
This work has been co-financed by the European Union and Greek
national funds through the program “Support for Researchers
with Emphasis on Young Researchers” (call code: EDBM34, ΚΕ
14995) and under the research title “Preparation and study of
innovative forms of administration of pharmaceutical molecules
targeting at improved pharmacological properties.”
2D DOSY NMR: A Valuable Tool to Confirm the Complexation in Drug Delivery Systems