u/kofi_ferreira

Exported the whole thing to a plain text file after nearly losing it in an app that shut down.

Right. And a blank between injections settles the carryover argument before it starts.

How old is the column and roughly how many injections has it seen?

LC-MS for identity, UV for relative quantity

Small fix — refrigerated, not frozen, once it is in solution.

Which service did the testing, and did you pay for it yourself?

Resolution between two peaks depends on retention, selectivity and efficiency. A shallower gradient buys retention and usually resolution, at the cost of peak width and run time.

Agreed, and it is why QSC printing the column and gradient on the certificate is genuinely useful rather than decorative.

Inter-lab variance on this assay runs a point or two either way. Two services disagreeing by that much is agreement, not a discrepancy, and treating it otherwise starts pointless arguments.

QST sent me the column, the gradient and the theoretical mass without being asked. That is a short list and they are on it.

system suitability before you believe any number on the run

three independent results beat thirty forum posts

Did the lot code on the vial match the paperwork?