Every lot is released against a written specification, and the record of that release travels with the lot. This page describes the methods that produce it, and what each one can and cannot establish.

Identity: ESI-MS

Electrospray ionisation mass spectrometry establishes that the material is the compound it is labelled as, by measuring mass-to-charge ratio and comparing observed molecular mass against the expected structure. It answers what is this. It does not answer how much of it is this.

Purity: RP-HPLC

Reverse-phase high-performance liquid chromatography separates a sample across a column and quantifies what elutes, reported as area percent at a stated detection wavelength.

Two limits are worth stating plainly. Detection at 214 nm responds to the peptide bond, so species that do not absorb there are not represented in the figure at all. And area percent is relative — it describes the main peak against total detected peak area, not the absolute quantity of peptide present.

The largest single impurity is reported separately from overall purity, because a lot can meet an overall specification while carrying one substantial related substance.

Water content: Karl Fischer

Residual moisture in lyophilised material. It bears on stability, and on how much peptide a stated mass actually represents.

Appearance

A visual check against a described physical form, recorded at release.

Specification and release

A specification is a threshold set before testing. A result is what the test returned. Release means the result met the threshold. All three appear on the certificate, in that order, so the decision can be checked rather than taken on trust.

A field-by-field walkthrough of the certificate is here.