has proper occurrent part gas chromatography-mass spectrometry time-of-flight mass spectrometry gas chromatography time-of-flight mass spectrometry A method where a sample mixture is first separated by gas chromatography then sample ions with different masses are accelerated to the same (known) kinetic energy and the time taken for each ion to reach a detector at a known distance is measured. This time is dependent on the mass-to-charge ratio of the ion. CHMO:0000735 GC-TOF-MS gas chromatography