My experience of Carryover contradicts the reply above. I am posting it as a data point rather than as a refutation, because one person's experience is exactly that.
Topic summary
Carryover and the ghost peak from last week's standard — what changed since
This is a generated summary. It shows the 9 most-liked posts from a topic of 115, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.
Peaks that do not elute do not appear in the area percentage. Aggregates and strongly retained species can be entirely invisible to a standard method, which is a ceiling on what any purity figure can claim.
Not disagreeing with anyone above, just adding the bit I keep having to look up.
28 likes 2mo
Confirming post #28 from a second method, which matters more than confirming it from a second person.
Mobile-phase preparation is a genuine source of between-laboratory variation. Acid concentration and organic modifier both shift retention, and neither is usually specified to the precision that would matter.
Someone should write this up properly, and it should probably not be me.
31 likes 1mo
Answering the question post #44 raises rather than the one it answers.
Since Carryover keeps coming up, it should probably be a maintained page rather than a recurring thread. I am happy to draft it if someone with more direct experience will review it.
31 likes 1mo
The arithmetic in post #50 is right; the assumption feeding it is the part to check.
A relative retention time against a known peak travels much better than an absolute one, and almost nobody reports it.
It cost nothing to check and would have cost something not to.
27 likes 1mo
r.marsden, post #63: The honest answer on Carryover is that it depends, and the useful part is the list of what it depends on. Four items, in rough order of how much they matter. Most people get the first two right and then argue about the fourth. Go to post
Carryover is a question about a distribution, not about a value, and treating it as a value is what produces the confident wrong answers.
i.ilunga, post #22: I would rather this thread reach "we do not know" about Carryover than reach a confident answer that nobody can support when asked. Go to post
I would be cautious about generalising from the Carryover example above. It is a good example. It is one example.
a.aguirre, post #5: Saving this. It is the version I will quote when the question comes round again. Go to post
Reversed-phase separates on hydrophobicity. A peptide is retained on a non-polar stationary phase and eluted by increasing organic solvent. For peptides the mobile phase almost always contains an ion-pairing acid, typically 0.1% TFA, which suppresses secondary interactions and sharpens peaks.
I would put a moderate confidence on that and no more.
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