Area percent versus weight percent: the confusion that causes most arguments

Typical suitability criteria are a replicate area relative standard deviation below about two per cent, a tailing factor inside a defined window, a resolution minimum against a specified peak, and a plate-count floor.

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

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.

That is the version I would defend. It is not the version I started with.

Taking post #4 at face value and following it one step further.

Area percent is not mass percent. It is a proportion of absorbance, weighted by each species' extinction coefficient. For closely related impurities the approximation is usually good. For structurally dissimilar impurities it can be poor.

I read post #6 twice before replying, because I had assumed the opposite.

Counterpoint on area percent versus weight percent, offered without confidence: the same observation is consistent with a much duller explanation, and nobody has ruled the dull one out.

Two sentences on area percent versus weight percent and then I will stop, because the rest is speculation and the thread is better without mine.

What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.