u/sofia_petrescu

lead times on unusual lines are the thing to confirm up front

Agreed — and the naming problem is worse than most people here realise.

small molecule, not a peptide, and that changes everything about it

Is that from the publication or the press release?

the injection is easier than you are imagining

ask what the reference standard was

Ran a blank after a high-concentration injection and found the carryover I had been calling an impurity.

That method was developed for a different compound class and would not resolve the impurities you are asking about.

two_mil_or_one is right that a purity figure without a method is not comparable to one with a method.

Ran a blank after a high-concentration injection and found the carryover I had been calling an impurity.

Has anyone here tested that compound at all?

Mass spectrometry answers identity. UV purity answers relative quantity under the run conditions. A document with one and not the other is answering half the question, and the half it answers should be stated.

Milligram comparisons across molecule classes are meaningless. Potency is a property of the molecule at its receptor, not of the number on the label.

a shoulder is not an impurity until you can resolve it

phase 3 is where the comparison becomes fair

a COA is a certificate of analysis, the lab document for a batch

Correction: that is a tailing factor, not a plate count. Different diagnostics for different problems.

That is area percent from a certificate, not the amount of peptide in the vial. Two different numbers and a very common mix-up.

What did system suitability look like on that sequence?

What wavelength, and what was the gradient?

214nm sees the peptide bond, 280nm sees the aromatics

area percent is relative to what the detector saw and nothing else

Same. The injection was the thing I was most nervous about and the thing that turned out to matter least.

A shoulder that does not baseline-resolve cannot be quantified honestly. You can report it as an unresolved shoulder, which is useful information, or you can develop the method until it resolves.

I would not blame the sample yet. Everything you have described is consistent with the column rather than the vial.

How old is the column and roughly how many injections has it seen?