Endotoxin testing methods — what worked for you?

Clinical perspective, offered as context rather than as advice.

Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight. This confirms identity — not just purity.

Why this matters: HPLC can show you a "pure" compound, but if it's pure of the WRONG compound, purity is meaningless. Mass spec at m/z 4113.58 Da confirms it's actually semaglutide. My Janoshik report includes both HPLC and mass spec.

If your testing provider only offers HPLC, consider upgrading to include mass spec for at least your first batch from a new vendor.

Dr.PathRoch said:

Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight.

Mine went the same way, slower.

Dr.PathRoch said:

Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight.

Coming at Dr.PathRoch’s question from a different direction. It is worth asking what the claim would look like if it were false. If nothing would look different, it is not a claim about the world and no amount of discussion will settle it.

One concrete data point for the thread. Give anything pharmacological four weeks before you judge it, and give anything measured weekly a four-point rolling average before you call it a trend.

I would rather be corrected than agreed with, if it comes to it.

OP back with an update, since a thread like this is useless without one.

Late follow-up. I did not do what was suggested, I did something adjacent, and it worked; posting the difference in case it matters to somebody.