AX-R06 — Recovered mass outside label claim tolerance

This is the rule that matters most to anyone buying by the milligram, and it is the one that fires most often.

A vial labelled 10 mg contains a lyophilised cake. That cake is peptide, plus water, plus counter-ion, plus residual solvent and inorganic residue. If the cake weighs 10 mg gross and is 82 % peptide by weight and 98.7 % pure, the vial contains 8.1 mg of the target compound — not 10 mg, and not 9.87 mg either. The arithmetic is set out with a worked example on /methods/peptide-content-vs-purity/ and is implemented in the purity-to-mass calculator.

A label-claim shortfall is an arithmetic consequence of how a claim is written, not a finding about anyone's intent. A nominal fill mass declared without water and counter-ion beside it will read short the moment the gravimetry is done, however good the material is. The effect is modest and well characterised: the index's median recovery against label claim is 98.3 %, the 10th percentile is 90.4 %, and the distribution is what a gross-mass fill against a peptide-mass claim predicts. Where the certificate states the content basis — and most of the certificates in this index do — the recovered mass can be worked out to within a percent before the vial is opened.

The tolerance of ±10 % is the index's own and is generous. A pharmacopoeial content uniformity requirement would be considerably tighter.