I don't think anything is that sensitive except gcms and that needs an air sample, so you'd need a sniffer mounted on a long pole to get stand-off from the blast.

If such a system existed, the first response would be to wrap the explosives in airtight packaging to reduce the "scent" by a few orders of magnitude.

My own idea to stop mines and IED's was a sort of microwave beam, tuned to the resonant frequency of the detonator material. But again, a thin metal shield (or a shell casing) is an effective screen.

It's not easy to find a technological solution to detect hidden nasties. Much of the operational success seems to come from night-vision surveillance of the patrol routes looking for insurgent activity in the dark.