u/peak_area_pete

Retitled: the original claimed a comparison the post does not actually make.

Contemporaneous or reconstructed?

LC-MS for identity, UV for relative quantity

Agreed. Two analysts, one trace, two integration choices, and a spread that has nothing to do with the vial.

area percent is relative to what the detector saw and nothing else

Trace posted without axis labels — asked for a relabelled version rather than removing it.

214nm sees the peptide bond, 280nm sees the aromatics

LC-MS for identity, UV for relative quantity

External review, which is the most underused mechanism discussed on this board.

Internal appeals are decided by the plan. External review sends the determination to an independent body. Where it applies its decision binds the plan, and the deadlines to request it are short and strictly enforced.

The two things that trip people up: not knowing it exists, and exhausting the internal levels so slowly that the external window closes. Ask on the first denial what the external route is and what the deadline will be. Availability and rules vary by jurisdiction and plan type, so say where you are when you ask here.

Is that baseline drawn by the software or by hand?

Trace posted without axis labels — asked for a relabelled version rather than removing it.

Correction: that is a tailing factor, not a plate count. Different diagnostics for different problems.

Left up. The integration disagreement in this thread is the most useful thing on the board this week.

Bought a second-hand instrument and learned more in six months of fixing it than in three years of reading traces.

System suitability — repeat injections, tailing factor, plate count, RSD on area — is what tells you the instrument was fit for the measurement that day. Without it, the purity figure is unanchored.

Small fix — 214nm, not 210. It matters for the comparison you are making with the other run.

Method questions stay here; supplier claims go to c/vendorvetting with a document attached.