How to Read a Peptide Certificate of Analysis

A Certificate of Analysis (COA) is the primary evidence a laboratory has about the identity, purity, and quantity of the material in a vial. For a research peptide, it is also the single most useful document for judging whether a supplier is trustworthy. This article walks through what a real COA contains, what each measurement actually tells you, and the specific red flags that indicate a document is decorative rather than diagnostic.

What a COA is

A COA is an analytical report produced by a laboratory that received a sample of a specific batch and ran a defined set of tests on it. For research peptides, "real" COAs are produced by independent third-party analytical laboratories — organisations whose business is analytical chemistry and who have no commercial stake in the outcome of the test. Two labs commonly seen in this space are Janoshik Analytical and Freedom Diagnostics. Both are examples of independent labs; both publish reports that can be verified against the issuing lab's system.

A COA that is generated by the seller and never touched by an independent lab is not third-party. It is a claim.

The methods you should see: HPLC and MS

A competent peptide COA reports at least two techniques.

High-Performance Liquid Chromatography (HPLC)

HPLC separates the components of a sample by pushing them through a chromatographic column under high pressure. Each component elutes at a characteristic time and produces a peak on the chromatogram. Peak areas are integrated, and the reported "purity %" is typically the area of the main peak divided by the total peak area (area-percent).

What area-percent tells you: how much of what the UV detector saw at that wavelength was the peptide of interest, versus other UV-absorbing species (fragments, side-products, residual reagents).

What area-percent does not tell you: it is not a mass fraction. Non-UV-absorbing impurities (residual salts, water) are largely invisible to a standard HPLC-UV method. A 99% area-percent number is not the same as "99% of the powder in the vial is peptide."

Mass Spectrometry (MS)

MS confirms identity. The instrument measures the mass-to-charge ratio (m/z) of ions produced from the sample. A real peptide COA will report a measured mass that matches the theoretical monoisotopic or average mass of the target peptide, usually to within a fraction of a Dalton for a well-calibrated instrument. Common ionisation methods are ESI (electrospray) and MALDI.

What MS tells you: whether the main peak on the HPLC really is the peptide it claims to be.

Without MS, a high HPLC purity number is not enough — the main peak could, in principle, be the wrong peptide entirely.

Reading a real report end-to-end

When you open a peptide COA, look for the following:

1. The issuing laboratory's name, address, and report identifier. A real report is issued by a real company at a real address, with a unique report number you can quote back to them.
2. The sample identifier and lot / batch number. Every vial on the supplier's shelf should be traceable to a lot; every lot should be traceable to one specific COA.
3. Analytical methods. The report should name the techniques used (e.g. RP-HPLC with UV detection at a specified wavelength; ESI-MS in positive mode). Vague reports that just say "purity: 99%" without stating how are less informative than they look.
4. The chromatogram itself. A real report includes the chromatogram image. You should be able to see the main peak, retention time, and integrated peak table.
5. The mass spectrum. A real report includes the mass spectrum with the observed m/z and the assigned charge state, and states the theoretical mass for comparison.
6. Date of analysis. COAs are batch- and time-specific. A report from three years ago on a different lot number tells you very little about the material you actually received.

What "purity %" actually measures

Restated as a checklist for a reader:

• Purity is usually area-percent by HPLC-UV at a stated wavelength.
• It captures UV-absorbing impurities relative to the main peak.
• It does not capture residual salts, moisture, counter-ions, or anything else the detector does not see.
• A high purity number is meaningful only alongside a mass-spectrum confirmation that the main peak is the intended peptide.

A COA that lists a purity number without either a chromatogram or a mass spectrum is not giving you enough information to act on.

Red flags

Some patterns should make a researcher pause:

• No lot number. Without a lot, the COA is not tied to the material in the vial.
• No issuing laboratory name. "Independently tested" with no lab named is not independent.
• Self-reported purity. A number that appears only on the seller's marketing page and never on a lab report.
• A single COA re-used across every product. Real batches produce real, distinct reports.
• No chromatogram, no spectrum. A purity number that is not backed by the underlying data.
• A COA older than the manufacturer's stated shelf-life for that lot.
• PDFs that have clearly been edited — different fonts inside the same table, misaligned rows, watermarks that don't belong to the lab.

Verifying a COA

The strongest form of verification is checking the report against the issuing laboratory's own system. Independent labs like Janoshik Analytical and Freedom Diagnostics maintain report databases you can query with the report identifier. If the number on the paper matches a record on the lab's system, the document is genuine. If it does not match, or the lab has no record, that is the entire story.

At Hermetica, every published third-party report is listed on the Certificates of Analysis page with the issuing lab and batch reference so a researcher can perform this check directly.

A COA read this way — methods, lot, chromatogram, spectrum, verification — is what makes a research peptide a defensible reagent rather than an act of faith.

Worked examples of every field described above appear on the certificates we publish. The full set is in the COA library, and each lot is linked from its product page — see BPC-157 or MOTS-c for a current example.