@Archer The thing to remember is that curiouscat is a chemical engineer involved with process improvement & control so identifying small impurities are important to work out how & why the yields are less than he wants. Then he can work out if improving the yield is cost effective for that particular process.
Your background is I think in analysis for regulatory control and proving a particular component is a controlled substance is your focus and so other minor impurities are not that important.
Those two roles are not really complementary.
My background is as a practical lab/plant chemist involved with process development & scale up so I can see where curiouscat is coming from which is why I posted the advice I did. Then you posted the exact opposite which wound me up so I apologise if my reply to you seemed a bit sharp. I can see from your reply to me that your posts were due to a minor comprehension error rather than a case of Maslow's hammer.
No harm done, I was contradicting sound advice so your response was considered and polite relative to what you were probably thinking.
You and I have similar backgrounds in processing, my current role is the analysis you describe.
If we made something then minor impurities were things which were removed after the initial identification of the target molecule, then they would be identified at a later date after purification often used as standards for future process monitoring. One time an impurity turned out to be a valuable commodity.