What are the exact problems you are having (can you, for example, show some spectra)?

Both of the methods you mention are dependent on the C-H coupling constant, and typically a default value of 145 Hz is used. Some couplings are, however, quite far from this, for example terminal alkynes in which the coupling constant is about 250 Hz causing them to give negative peaks in DEPT135 even though they are CH carbons.

Due to the same reason, it is common to see small signals from other than CH carbons in DEPT90 spectra.

Dear Jani Rahkila

I am using the default Bruker DEPT135 parameter set, in which C-H coupling constant is indeed 145 Hz.

The problem is that the signals appear in a way that makes it impossible to phase them all appropriately (see the attached photo). If you phase some, others will not follow and remain unphased, whatever the phasing protocol.

Could it be because of bad 13C P90 value (from which all the other pulses are calculated)?

It could be the 90° pulse (and the different DEPT experiments are named after the flip angle of the last pulse), but especially the DEPT135 experiment is not so sensitive to it being off by a little bit. For very salty samples it can of course be a problem.

By looking at your spectrum, however, my initial guess is that the phasing is just off. I would start by zeroing the 0th and 1st order phase correction values, then set the pivot point on the signal at 10 ppm and use the 0 order correction to phase it positive, then use the 1st order to try to correct the rest.

Is there any chance to have a look at the raw data set?

Jani Rahkila I sent you a message with the raw data. Thank you for your help.