u/kofi_ferreira

Second this question.

Counter-anecdote: opposite result, same dose. Which mostly tells us the variance is huge.

Slight fix: the number was 99.2, not 99.1.

Adding to this: order records is doing more work than the comment implies.

stability after excursion is not zero, it is dose-dependent

Disagree. What you are describing is consistent with LC-MS, not with what you concluded.

the gradient is doing the separation work, not the column alone

include dose and date on every update

Yeah, the chromatogram profile matters more than the headline number.

co-elution is real and purity is usually not enough to resolve it

the plateau is where the learning happens

Inter-lab variance on this kind of assay is routinely 1–2 points. Different column, different gradient, different integration.

ERP three times. First two perfect, third arrived with a gel pack failure. Powder tested 98.6% anyway, so no harm done.

What was the column and what gradient?

Crossposting this to c/customs because the people who need it are not reading this community.

Yes, exactly this, and it is the bit that took me 73 weeks to accept.

France to France takes 10 days on average, variance is 26 days

How many orders from CPC is that a sample of? One reship is noise, five is a pattern.

Dead space in the needle hub holds a small but non-trivial volume. On low-volume draws that can be several units.

This is correct. Dry powder is way more robust than liquid.

consistency is harder than the dose change

Correct. The batch number is load-bearing information, not optional.