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How to read a certificate of analysis

A certificate of analysis is a measurement report, not a guarantee. Read correctly it tells you what was measured, on what material, by which method — and, just as importantly, what was not measured.

Last updated August 5, 2026DocumentationReviewed by the PrimeGen Co. laboratory documentation team

The fields that matter

Most disputes about peptide quality come down to reading a certificate loosely. Work through the fields in order and treat any missing field as an unanswered question.

Certificate fields and what each one establishes
Field	What it establishes	Failure mode if absent
Product and sequence	Which compound was analysed	Cannot confirm the report belongs to the material
Lot number	Which production batch the result applies to	Result cannot be tied to the vial in hand
Analysing laboratory	Who performed the measurement	No accountability for the figure
Report and analysis dates	When the material was measured	Cannot judge how current the data is
Method	How purity and identity were determined	Figures are not comparable between suppliers
Purity result	Chromatographic purity of the main peak	No quantitative claim at all
Observed mass	That the main peak matches the intended sequence	Purity may describe the wrong molecule

Certificate fields and what each one establishes

Purity is a chromatographic statement

A purity figure such as 99.2% normally means that the main peak accounts for 99.2% of the total integrated peak area detected under the stated chromatographic conditions. It is a relative statement about what the detector saw, not an absolute statement about the contents of the vial.

Species that do not absorb at the detection wavelength, or that do not elute under the gradient used, are not represented in that number. This is why counter-ion content, residual solvent and water content are handled as separate determinations rather than being folded into a single figure.

Identity is a separate question

Mass spectrometry answers a question chromatography cannot: is the main peak the intended sequence? A truncated or deletion analogue can chromatograph cleanly and produce an excellent purity figure while being the wrong molecule. The observed mass on the report should agree with the theoretical mass for the stated sequence within the instrument's expected tolerance.

What a certificate does not tell you

A certificate describes the material as analysed at the time of analysis. It does not describe how the vial was stored after it left the facility, it does not establish biological activity, and it is not a safety assessment. It is also not a statement of suitability for any use in humans or animals — research material is supplied for laboratory research only.

Frequently asked questions

Why is the certificate digital rather than enclosed in the box?

A digital document can be version-controlled, superseded and re-verified against the lot record. A printed sheet in a shipment cannot be audited later, and cannot be checked before ordering.

Can I request the raw chromatogram and mass spectrum?

Yes. Underlying chromatograms and spectra for a released lot can be requested through the certificates page or from laboratory support.

Does a higher purity figure always mean better material?

Not necessarily. Purity figures are only comparable when the method, column, gradient and detection wavelength are comparable. A figure quoted without a method should be treated as unverified.

Related research compounds

Compounds with a published certificate of analysis, where the methodology described on this page can be read against a real lot record.

References and standards

USP <1225> Validation of Compendial ProceduresUnited States Pharmacopeia
ICH Q2(R2) Validation of Analytical ProceduresInternational Council for Harmonisation

Editorial attribution

PrimeGen Co. laboratory documentation team

Editorial and analytical documentation

Our documentation team maintains lot records, certificate presentation and the educational material on this site. Pages describe our own internal practices and published analytical methodology; they are not an independent certification of any kind.