Most nasty stuff is present in vanishingly small quantities compared to all the other crap in biomaterial, which is why most contaminant testing involves an ext

Most nasty stuff is present in vanishingly small quantities compared to all the other crap in biomaterial, which is why most contaminant testing involves an extraction step, or even extraction+fractionation, before spectrometry. Somewhat relatedly, inorganic ions don't have nir activity, only their complexes with organic counterions have nir activity. And there are like a gazillion different things that complex with lead/mercury/etc. in unpurified biomaterial, so direct nir measurements of a sample are not a productive approach. That being said, it would certainly be a big moneymaker if placebo contaminant detectors became a thing with Chinese consumers like surgical masks for smog