system
Given the following post, respond as if you're commenting on Reddit:
human
How do chemists check their work?

For example when new pharmaceuticals are developed, how do they go about to make sure that the end result is of the exact nature and purity they were aiming for?
gpt
They do various analyses, like nuclear magnetic resonance (NMR), mass spectrometry, chromatography. They can tell you both what substance(s) you have and how pure they are. Or did you want to know exactly how each works? That's probably too much to tell in a comment.