[Discussion] we are measuring handling at the wrong time and calling it noise

The title is the argument: we are measuring handling at the wrong time and calling it noise. Here is the rest of it.

For any compound with a thin testing history, identity is the first question. Mass spectrometry against a theoretical mass answers it; an area-percent purity figure does not.

On the thin testing history in this board, and what to do about it.

Most of the compounds discussed here have a handful of independent results across the entire site, and several have none. That is a fact about how few members have paid for testing, not a judgement about the material.

What follows: buy small, test identity first for anything unusual, and post the result even when it is unremarkable. The vendor source pages are built from exactly these submissions, and the compounds with the thinnest coverage are the ones where one more entry changes the picture most. Research material is not approved for human use, so what this board can usefully build is an analytical record.

Why purity and net content diverge, and why that is usually honest.

Purity by area percent is a relative measure of what the detector saw. Net peptide content subtracts counterion, water and residual solvent from the powder mass. For some compounds in this catalogue the gap between the two is large.

A vial can therefore be 99% pure and contain considerably less peptide by mass than the label weight suggests, with nothing wrong anywhere. The problem is not the chemistry; it is that people compare a purity figure from one supplier with a net content figure from another and conclude something about both. Ask which number you are being shown, every time.

If somebody has the same thing measured a different way, post it next to mine and we will see whether they agree.