How to Read a Peptide Certificate of Analysis (COA)

A Certificate of Analysis is the document that tells you what is actually in a vial. For research compounds it is the single most important piece of paperwork attached to a batch — and yet many suppliers either don't publish one, or publish something that looks official without containing meaningful analytical data. This guide explains how to read one properly.

What a COA is

A Certificate of Analysis is a report issued by an analytical laboratory documenting the tests performed on a specific batch of material and the results obtained. The key phrase is specific batch. A COA describes one production lot, not a compound in general.

Batch-specific vs. compound-level data

This is the most important distinction, and the one most often blurred. A genuine COA is tied to a unique batch identifier and reports what that particular lot tested at. Some suppliers instead publish generic reference data for a compound — a document that describes what the compound should look like rather than what their material actually measured. That is not batch verification, and it tells you nothing about the vial in your hand.

When you look at a COA, find the batch or lot number first and check that it matches the vial.

Identity confirmation

The identity test confirms the material is the compound it claims to be. This is typically established by mass spectrometry, which measures molecular weight — a compound's molecular weight acts as a fingerprint. If the measured mass matches the theoretical mass for that peptide sequence, identity is confirmed.

Purity and the HPLC chromatogram

Purity is usually determined by High-Performance Liquid Chromatography (HPLC). The sample is passed through a column that separates its components, and a detector records what comes out and when. The result is a chromatogram — a graph with peaks.

The main compound produces a large peak. Impurities produce smaller peaks. Purity percentage is calculated from the area of the main peak relative to the total area of all peaks. So a result of 99.4% means the target compound accounts for 99.4% of the detected material.

When reviewing a chromatogram, a single dominant sharp peak is what you want to see. Multiple substantial peaks, or a broad and poorly resolved main peak, suggest a less clean product.

Quantity

The quantity test confirms the vial contains the mass it claims. A vial labelled 10mg should test at or near 10mg. Reputable results often come in marginally over the label claim — a 10mg vial testing at 10.2mg is normal and generally reflects deliberate slight overfill.

Dates

A COA should carry dates: when the sample was received, when the analysis was performed, and when the report was issued. These let you judge how current the testing is relative to the batch you are receiving.

Redactions

Some identifiers on a published COA may be redacted — typically internal task or reference numbers. This is normal practice to protect supply-chain relationships and prevent third parties from misusing report numbers. Redaction of administrative identifiers does not affect the analytical validity of the results. What should never be redacted are the compound name, batch identifier, test methods, or the results themselves.

Warning signs

• No batch number, or a batch number that doesn't match the vial
• No named laboratory — you should be able to see who performed the analysis
• No chromatogram — a purity percentage with no supporting data is just a claim
• Identical documents across different products — a sign of generic rather than batch-specific testing
• Suspiciously perfect results — real analytical data has variation; every batch reading exactly 99.9% is implausible

How we publish ours

Every batch we supply is independently analysed by a third-party laboratory using HPLC-MS. Each lot receives a unique batch identifier, and the corresponding Certificate of Analysis — including the chromatogram — is published on our Lab Results page. You can review the paperwork for a batch before opening a vial, and compare the batch identifier on the document against the one on your product.

Research use only. All compounds referenced are intended strictly for laboratory and analytical research. They are not medicines, supplements or therapeutic goods, and are not for human or veterinary consumption.