Increase the concentration of sample and number of scans.

Dear Clemens Anklin, But the DMSO peak has a quaternary carbon as well, seen in HMBC only. I am interested in this particular carbon. Will a DEPT help me with this cause I will not see a quat  in DEPT it right? What if I run a APT experiment with a relaxation delay of 1/2J. Will this remove all my other carbons along with the methyl group of DMSO and just the quats remain?

Thank you Dr Anklin. I will try this.

If they have proton attached, you should try try with 2D-HSQC, otherwise with HMBC.

Good luck

There are no Protons attached.

HMBC detects coherences up to 5 bonds, if accurately done

A simple way it to run a spectre of dmso alone, scale it so it fits the dmso signal in your sample and subtract them.

Assuming that the 13C peaks that you are looking for do not have the same relaxation rate as the DMSO-d6 signal, you can try a 180°-delay-90° inversion-recovery experiment and choose the recovery delay such that the solvent signal is nulled. You will then see your signals, albeit not with their original intensities. (Admittedly, this is an experiment of the old school.)

 It depends on what your equipment is capable of. If your equipment can perform simultaneous 1H and 2H decoupling, follow the suggestion by Clemens Ankins; if not, try the method suggested by Ludger Ernst (nothing wrong with an "experiment of the old school"!). Petersen's subtraction method might work, but may be a bit tricky. Always try the simplest method first. Good luck.