Reference · documents

A certificate, field by field

The annotations below explain what each line establishes and — more usefully — what it does not. Values are illustrative and describe no real lot.

Lot identifier

EXAMPLE-A1 Must also appear on the physical unit. A certificate whose identifier matches nothing you can hold links the document to no object.

Compound

Reference peptide A (15-mer) The declared identity. Everything below is measured against this claim — it is the hypothesis, not a finding.

Declared net weight

5 mg Gross fill weight as labelled. Not the mass of the target compound present — see net peptide content below.

Identity — method

LC-MS (ESI+) Absence of this line is the single most consequential omission on a certificate. Without it nothing confirms the material is what the top line claims.

Identity — result

1419.6 Da observed / 1419.5 Da expected Observed against theoretical mass. Both figures should be printed. A verdict with no numbers cannot be checked.

Purity — method

RP-HPLC, C18, 220 nm, 0.1% TFA / MeCN gradient Technique, column, wavelength and mobile phase. A purity figure quoted without this line is not interpretable.

Purity — result

98.4 % area Proportion of total detected peak area. Area percent, not mass percent, and only of what the detector could see at that wavelength.

Chromatogram

published, axes labelled The trace itself, with a scaled and labelled time axis. A purity number with no chromatogram is an assertion; with one, it is checkable.

Net peptide content

81.2 % w/w (nitrogen determination) How much of the fill mass is actually peptide. The balance is water and counterion. A vial can be 98% pure and 81% content simultaneously — both figures are correct and they measure different things.

Water content

4.1 % w/w (Karl Fischer) Lyophilised material is hygroscopic. Part of the gap between purity and content.

Counterion

TFA, 12.8 % w/w Residue of the purification step. Accounts for most of the remaining gap, and is not an impurity in the chromatographic sense.

Endotoxin

< 0.5 EU/mg (LAL kinetic chromogenic) A separate assay. Chromatography cannot detect endotoxin — its absence from a report means it was not tested, not that the result was good.

Sterility

not performed Stated explicitly rather than omitted. A report that says "not performed" is more informative than one that stays silent.

Laboratory

Reference Laboratory A · ISO/IEC 17025 Named, with its accreditation and scope. An unnamed laboratory cannot be checked against any register.

Relationship to supplier

no ownership or financial link Rarely printed, and the line that decides whether "third-party" is accurate. Accreditation does not cover it.

Dates

manufactured 2026-02-11 · sampled 2026-02-19 · reported 2026-03-02 Three dates in a coherent order. A report dated before manufacture describes a different batch, whatever identifier it carries.

Signals

What a complete report looks like

Both identity and purity are reported

Two measurements answering two questions. Either alone leaves a gap the other closes.

The chromatogram is published with labelled axes

Lets the reader see peak shape, baseline behaviour and whether the main peak is resolved.

The method line is complete

Technique, column, wavelength, gradient. Enough to repeat the analysis.

Net peptide content is stated separately from purity

Signals that the issuer knows the difference and expects the reader to.

Assays not performed are named as not performed

Disclosure of scope. Silence and "not performed" are very different statements.

The laboratory is named with its accreditation

Verifiable against a public register in a couple of minutes.

What should stop you

None of these prove misconduct. Each one means the document cannot support the conclusion usually drawn from it — which is enough reason to ask for the missing piece.

Purity quoted with no method

"99%+" with no technique, wavelength or gradient describes nothing reproducible.

No mass confirmation anywhere

Purity without identity establishes uniformity, not what the material is.

No chromatogram, or an unlabelled image

A trace with no axes or scale cannot be read and functions as decoration.

The laboratory is not named

Nothing to check, no register to consult, no accreditation to verify.

Identical traces across different products

Matching baseline noise or retention times across distinct compounds indicates a reused document.

Dates missing or out of sequence

A report predating manufacture cannot describe the batch it is attached to.

Lot identifier absent from the physical unit

The document and the object are unlinked; the certificate could belong to anything.

Purity and content presented as one figure

Conflating the two overstates how much target compound is present.

The question worth asking first

Before any of the above: does the lot identifier on the document match the one on the object in front of you? If it does not, nothing else on the certificate is relevant. A perfectly executed analysis of a different batch tells you nothing about this one, and it is the most common disconnect between a report and the thing it is offered as evidence for.

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