I would never ever in a million years trust something colorimetric that costs $2 and is supposed to identify a range of substances against literally everything else. Allow me to explain. It’s one thing when you’re talking about a pregnancy test, for instance. Those are very reliable, but they’re reliable because they’re only ever tested against urine. People don’t expose them to sandwich crumbs or aspirins, they don’t douse them with mystery liquids, and the molecules you’re looking for are huge protein structures.
Cocaine, meth, or THC all have comparatively abbreviated structures with relatively few active sites. You can look at my explanations in the ELI5 thread for some details on how chemists resolve detailed structures, but the gold standard here is still GC-MS. This technique sort of produces basically a molecular fingerprint and doesn’t rely on the faulty flow-chart logic of, “If it reacts or binds with this, this, and this, it must be this.” I’m not familiar with the exact chemistry of these strips, but we’ve already seen that they can be fooled by random debris, so I’m assuming that they use at least some kind of faulty reactive system.
I suddenly have an idea for a YouTube video.
