Coming back to: Resolution and tailing factor: real acceptance criteria posts 91–113

On post #90 — agreed on the reasoning, with one qualification.

Particle size and column dimensions determine what resolution is achievable at all. A 5 micrometre 250 millimetre column and a sub-2 micrometre 100 millimetre column are different instruments in practice.

Careful with the language on Resolution and tailing factor. "Not detected" and "not present" are different findings and the first is a statement about the method.

I would keep Resolution and tailing factor and the decision it usually gets used for separate in this thread. They are related and they are not the same question, and merging them is why the last one went badly.

Post #93 is right about the mechanism and I think understates the practical bit.

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.

It is the kind of thing that is obvious once and never again.

This follows post #93 rather than contradicting it.

Small methodological point on Resolution and tailing factor: repeating a measurement is cheap and resolves most of what is being argued about here at no cost to anyone.

Useful. I have added it to my own notes with the date on it.

Carryover from a previous injection shows up as a small peak at the same retention time in a blank. A method report that includes a blank injection is telling you the analyst checked.

This is where my knowledge stops and I would rather mark the edge than blur it.

If two laboratories disagree by more than two or three percentage points, work through method, integration, sample handling, whether it was the same lot and the same vial, and whether suitability passed. After all five, a gap needs an explanation.

Reading it back, the second half matters more than the first.

The arithmetic in post #98 is right; the assumption feeding it is the part to check.

An honest declaration on Resolution and tailing factor: I have a prior here and it is strong enough that you should weight what I say downward. Stating it rather than hiding it.

Before anything else: what was the gradient, and at what wavelength? Area percent at different wavelengths is not the same number even on the same sample because different species absorb differently at different wavelengths. With the method stated, I can tell you something useful. Without it, all I can say is that there is one large peak.

That much is documented. The rest is how I have interpreted it.

Adding a data point of agreement rather than a data point.

Resolution and tailing factor is well covered in the tag pages, and the older discussions are better than the recent ones because they were argued out properly. Worth twenty minutes before adding to this one.

Reading back through the Resolution and tailing factor threads from last year, the same three questions come up every time and only one of them has ever been answered properly. That seems like a documentation gap rather than a knowledge gap.