I was switching a column from FID detector to a Mass detector but keeping the same separation condition. I got similar signal for the first injection but after then no peak was detected following the same injection. The only thing I got was a solvent peak. What is a possible reason causing that? Any comments are appreciated.

There are a numberof possibilities but one is that your filament burnt out (if you are using EI)

In subsequent injections do you now not even get a solvent peak?

Check for anything obvious like septum or leaks first

Try switching to your reserve filament. Filament life will longer if you switch it off during the solvent elution time.

Regards,

Ralph