No. It takes an incredible amount of energy (e.g. lighting strikes, high pressure at 600 degrees in the presence of a catalyst, highly specialized and evolved bacteria) to convert the nitrogen gas in the atmosphere to any useful form of nitrogen, such as nitrate, nitrite, ammonia, etc. Nitrates may be common, but they are almost universally the result of industrial chemistry used to create commercial and consumer products. (And possibly grilling protein at high temperatures )
Really? How? I guess you could use something like MALDI, but having done a few MALDI samples, I can pretty much guarantee it's not a feasible technology for our friends in blue at the moment. Even if there were a benchtop system that was easy-to-use, rugged, and eliminated the need for a skilled operator, it's almost inevitable that some molecules will break into sub components. Explosives, by their very nature, are not the most stable molecules.
Agree with everything you said, but I think there is a fundamental disconnect about the definition of a 'false positive'. I understand why golf shoes (heavy use of fertilizer on golf courses) and contact cleaning solution (hydrogen peroxide) and hand lotion (fragrance chemicals) may set off the detector, and that is technically not a 'false positive'.

However, from the perspective of airline safety, and the perspective of a passenger who was just groped, it is quite logical to consider those results to be a 'false positive', as they pose no safety threat.