How can GLC be used by forensic scientists

To try to determine the cause of a house fire where arson using petrol is suspected A sample of the material is placed in a sealed bag which is then heated in an oven. Any volatile components on the material will turn to gas and then can be removed using a hypodermic syringe. These are then injected into the injection port of the GLC. Samples of petrol are then analysed in the same way and the chromatograms are compared. If the peaks match (retention times of some of the peaks are the same) this would be evidence that petrol may have been used to start the fire