So you see everyone is having fun with this discussion if only because it clearly has nothing whatsoever to do with Arduinox.
While we have no doubt of your serious intent, and note you indeed have some experience with the Arduino platform, you are nevertheless in the same category as the "newbies" or rank beginners who come here and ask for advice in using an Arduino for something that fundamentally has nothing to do with microcontrollers of any sort.
Detecting explosives is a matter of chemistry. The instruments used for this are in general, variants of mass spectrometers or possibly nanotechnology sensors which react to specific molecules, possibly using biotechnology. Building a mass spectrometer is a substantial engineering task which just might - somewhere along the way - involve a microcontroller or two, but these would be very much peripheral aspects of the project as they would be for nanosensors.
It most certainly has nothing to do with electromagnetic field sensors because explosives per se are neither sensitive to, nor emit any form of electromagnetic field.
And the current situation is that despite considerable research, there is at least at present, little that is more practical in use than a suitably trained dog, or less expensive to maintain.