1μL injection on a restek 30 or 60 m column. 0.25 ID w 1.4 df film. Hydrogen or Helium. Used to analyze via SIM.

Are you trying to measute the DMSO or are samples in DMSO?

My sample is in DMSO. I prefer headspace GC, I cant find procedure for GC-MS in DMSO solution.

For Headspace unit: set the temperature of the oven, loop, needle (depending of the brand name of your Headspace unit) to a value that is below the boiling point of DMSO (189°C), let's say 120/130/135 °C. In this way you will vaporize only your compounds from your herbal extract.

For GC program it's suitable to start from 40°C and increase with a small temperature ramp (e.g. 5°C/min) to the final temperature of your column (read its specification) . In this way you'll be sure that you'll catch all the volatile and semi-volatile compounds in the extract.