Revisiting: Aggregates and why a purity assay may miss them entirely

Genuine question rather than a rhetorical one: has anyone here actually observed Aggregates, as opposed to read about it? The thread is long and I cannot tell.

Post #8 answers the question as asked. The question underneath it is different.

Truncation products: fragments from incomplete synthesis or from degradation. They elute quite differently from the intact peptide because they are much smaller and have different hydrophobicity. They are usually well separated.

Aggregates: multiples of the monomer mass. May not elute at all under a standard reversed-phase method. A species that does not come off the column does not appear in the area percentage.

I have said this before in a thread nobody could find, so it is worth repeating.

I read post #20 twice before replying, because I had assumed the opposite.

What I can speak to on Aggregates is narrow, so I will keep it narrow rather than generalising from it. Beyond that boundary I do not know.

I have no financial interest in anything named in this thread and I want to say so before I comment on Aggregates, because it is the sort of subject where it matters.

On Aggregates, the part that usually goes wrong is that the question is asked as though it has one answer. It has a range, and the width of the range is the interesting bit.

If you can post the two or three numbers you are working from, several people here will check the arithmetic rather than argue about the conclusion.

Trifluoroacetate is a counter-ion rather than an impurity, and it appears in the mass balance rather than in the chromatogram. Conflating the two accounts for several confused threads here.