I have a problem with my Thermo GC/MS-iontrap.
When I do an injection in full scan mode and I do a base peak with the ions I want to search for, my test compound is detected. If I do it in SIM mode, it is not detected. This is happening only in some compounds. In full it works fine but in SIM mode and MS/MS, it doesn't detect them. The technician does not give a solution to the problem. Someone can help me?

thanks