Understanding a Certificate of Analysis: What Every Buyer Must Verify

ACertificate of Analysis (CoA) is the single most important document a research buyer receives with a peptide vial. It is the supplier's written attestation, ideally referenced against independent testing, that the contents of a specific lot match the declared sequence at a declared purity. A research workflow that does not start with a verified CoA is a workflow without a baseline.

What a CoA actually is

A CoA documents the analytical results for one batch of one compound. It is not a generic product spec sheet. A defensible CoA names: the compound, the manufacturer's lot or batch reference, the assay date, the analytical methods used, the results, and the laboratory that issued the figures. If any of those fields is missing, the document is closer to marketing copy than to analytical evidence.

Who issues a credible CoA

The strongest CoAs are issued by a third-party laboratory that is independent of the synthesising facility. In-house CoAs are not inherently invalid, many synthesis partners run their own QC, but a third-party result removes the conflict of interest implicit in a supplier grading its own work. UK and EU research buyers should expect to see the issuing laboratory's name, address and accreditation status on the document, not only the supplier's logo.

Reading HPLC purity figures

High-Performance Liquid Chromatography (HPLC) separates a sample into its constituent peaks, with the area under the target peptide's peak expressed as a percentage of the total integrated signal. A figure of "≥98% HPLC area" means that 98% or more of the UV-detectable material eluting from the column corresponds to the target compound; the remaining 2% represents related impurities, deletion sequences or process residues that the method was able to detect.

"≥98%" is the practical floor for research-grade peptides. Below that, related-sequence contamination materially affects in-vitro work. A CoA worth its name shows the actual chromatogram or at minimum the integration table, not just a single headline number.

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A purity figure without a chromatogram is a claim. A purity figure with a chromatogram is evidence.

Mass spectrometry confirms identity, not just purity

HPLC tells you how clean the sample is. Mass spectrometry (typically ESI-MS or MALDI-TOF on a research CoA) tells you what the sample actually is. The observed molecular mass should match the theoretical monoisotopic mass of the declared sequence within the method's resolution. Identity confirmation is the step that distinguishes a verified peptide from a clean unknown, and it is the field most often missing from weak CoAs.

Matching lot numbers to vials

A CoA is only meaningful if it can be traced to the specific vial in your hand. Every vial label should carry a lot reference that appears, character-for-character, on the CoA. If a supplier issues a generic product-level CoA with no lot reference, the buyer cannot tell whether the document describes the material that was actually shipped. Lot-to-document traceability is non-negotiable.

Red flags on a research CoA

• Pooled or "representative" results covering multiple lots, each batch must be tested as itself.
• No lot or batch reference printed on the CoA, or a mismatch between the vial label and the document.
• No issuing laboratory named, or a laboratory address that cannot be verified.
• HPLC purity stated without a chromatogram or integration table backing the figure.
• No mass spectrometry identity confirmation for a research peptide sold as a defined sequence.
• Assay dates that pre-date the synthesis batch, or are absent altogether.

How FORM Peptides publishes records

FORM Peptides publishes a supplier-issued CoA/CoC and an HPLC test report on each product page, so buyers can cross-check the document that arrived in their vial box against the record before logging any in-vitro work. The methodology behind those records is documented in full on the quality and testing page.

A CoA does not replace a researcher's own analytical due diligence. It does, however, establish whether the supplier was ever willing to be measured against an independent yardstick, which is the question every research buyer should ask before placing a second order.