DEPT
DEPT (Distortionless Enhancement by Polarization Transfer)
The transfer of polarization from protons to carbon enhances the carbon signal strength by a factor of 4 approximately. By careful calibration of the decoupler power it is possible to create an edited spectrum using three pulse widths, 45, 90, and 135 degrees. Because quaternary carbons have no attached protons they are not detected.See HETCOR
for details on decoupler power calibration (see also Varian’s Guide to
NMR Experiments). It is essential that you have accurate values for pp
and pplvl.
Procedure:
- Requirements for sample – 100 mgs would be great, allowing a DEPT experiment
to be acquired in 10-20 minutes.
- Acquire a C13 spectrum.
- mp to a second experiment, join that experiment
- enter dept which will modify the parameters to the DEPT experiment.
- pw = pw90 on C13. This value should be correct or determine yourself.
- pp = 90 pulse on the decoupler channel
- pplvl=value at which pp was determined to be 90 degrees
- pp and pplvl are determine as described in the HETCOR doc.
- dmf and dpwr are moved into the dept experiment from the C13 experiment and should not require alteration.
- j = the average coupling C-H constant
- d1= a delay to allow proton relaxation to occur. 1-3 times the T1 of protons connected to C13 in your sample.
- dm = decoupler modulation and is set to ‘nny’, which is set by the dept macro.
- Adjust nt and acquire the spectrum(ga). If you have 100 mg of a sample MW around 400 nt=16 should give you good results.
Processing commands:
adept edits the spectra, and prints out results. Do not enter this command twice without first reprocessing the fids! If you want a print out of these results do: printon adept printoff
The adept command produces a text file dept.out in the current directory that contains the results of the analysis.
dssa displays the edited spectra
pldept plots the DEPT spectra
