Why one laboratory's 98.4% and another's 96.1% may not contradict — one year on

Everything in post #4 holds. The case it does not cover is the one I have.

Transfer between laboratories: a method can be transferred from one lab to another, but the receiving lab needs to demonstrate that they can achieve the same performance. This requires comparative testing and sometimes small method refinements.

Where a pharmacopoeial monograph exists, a method that follows it inherits a great deal of assurance. Almost nothing discussed here has one.

Post #7 describes the usual case. This is about the unusual one.

System suitability is the ongoing evidence that a validated method is still performing. Validation is done once; suitability is done every run, and it is the one that appears on a certificate.

Adding the measurement that post #11 says would settle it.

The most useful single question about a method: what would it fail to detect? Every method has an answer and few documents state it.

Answering the question post #11 raises rather than the one it answers.

The limit of quantitation determines what the impurity table can honestly contain. Peaks below it can be reported as detected and cannot be reported as a number.