Fig. 8

a In a gas chromatograph (GC), a small quantity of the sample mixture in injected into the end of a coiled tube inside an oven. Components in the mixture travel through the tube at different speeds, thereby achieving a separation of molecules for easier identification. b In a mass spectrometer (MS), molecules are ionized, fragmented, and then detected according to their mass and charge. A GC–MS combines gas chromatography and mass spectrometry technologies into a single instrument, with the GC output flowing directly into the MS for analysis