How to read a peptide Certificate of Analysis
A COA is the single most important document in research-compound sourcing — and the most commonly faked. This is how to read one properly: what the purity number means, how identity is confirmed, and how to tell a real certificate from a decorative one.
01What a COA actually is
A Certificate of Analysis is the analytical report a laboratory produces for one specific batch of material. It is not a marketing document and it is not a statement about the product in general — it describes the lot in your hand. A real COA answers two separate questions: how pure is it (by HPLC) and is it actually the compound claimed (by mass spectrometry). A certificate that answers only one has told you half of what you need.
02HPLC — the purity number
High-Performance Liquid Chromatography pushes the dissolved sample through a column that separates its components by how strongly each interacts with the column material. A detector records each component as a peak. Purity is the area under the target peptide's peak divided by the total area of all peaks, expressed as a percentage.
So "99% by HPLC" means 99% of the detected material is your target compound and ≤1% is everything else — truncated sequences, deletion products, or leftover synthesis solvents. The critical habit: always read the number next to its chromatogram. The chromatogram is the actual graph of peaks. A percentage printed without the chromatogram beside it is a claim, not a result — there is nothing to check it against.
03Mass spectrometry — the identity check
HPLC proves the sample is pure. It does not prove what it is. That is what mass spectrometry does: it measures the molecular weight of the compound and compares it to the theoretical mass of the peptide it is supposed to be. If the measured mass matches, identity is confirmed. A complete COA carries both traces — HPLC for purity, MS for identity — because a pure sample of the wrong molecule is still the wrong molecule.
04The anatomy of a real certificate
Every field below should be present. Missing fields are how you spot a certificate that was designed rather than measured.
05Real vs. decorative
The peptide space is full of official-looking documents that contain no actual data. The difference is not how polished the certificate looks — it is whether the claims are checkable.
A real COA
- Names the testing laboratory
- Has a unique lot number that matches your vial
- Shows the HPLC chromatogram, not just a percentage
- Includes a mass-spec trace confirming identity
- Is dated and often independently verifiable
A decorative one
- A headline "99%" with no chromatogram
- No testing lab named
- No lot number, or one that doesn't match the vial
- Purity only — no identity confirmation at all
- Reused across every product regardless of batch
Common questions
What is a Certificate of Analysis (COA)?
A COA is the analytical report a laboratory produces for a specific batch of material. For a research peptide it states the measured purity (usually by HPLC), confirms the compound's identity (usually by mass spectrometry), names the testing lab, and carries a unique lot number that should match the vial you receive. A COA describes one batch — not the product in general.
What does HPLC purity actually measure?
High-Performance Liquid Chromatography separates everything in the sample and measures the area under each peak. Purity is the target peptide's peak area divided by the total area of all peaks, as a percentage. “99% by HPLC” means 99% of the detected material is the target and ≤1% is everything else — truncated sequences, deletion products, or residual solvents. A purity number without the chromatogram beside it is a claim, not a result.
Why does a COA need mass spectrometry too?
HPLC tells you how pure the sample is; it does not prove what the compound is. Mass spectrometry measures molecular weight, confirming the peptide's identity matches its theoretical mass. A complete COA carries both: HPLC for purity, MS for identity. One without the other is only half the picture.
How do I tell a real COA from a fake one?
A genuine COA names the testing laboratory, carries a unique report or lot number, is dated, and shows the actual chromatogram and mass-spec trace rather than just a headline percentage. The lot number on the COA should match the lot on your vial. Independently recognized labs — Janoshik, MZ Biolabs, Colmaric — can often be verified directly. A single number with no lab, no lot, and no chromatogram is not a COA.
What purity should I expect for a research peptide?
≥98% is a common baseline for research supply and ≥99% is widely available. Below 95% generally indicates the synthesis or purification did not go cleanly. The right threshold depends on the study: a binding assay tolerates less than a kinetics experiment. Always read the number against the method and the chromatogram, not on its own.
Should the COA match the exact vial I received?
Yes. A COA is batch-specific, so the lot number printed on the vial should match the lot on the certificate. A COA for a different lot tells you about material you did not receive. Reputable suppliers make the current batch's COA available and tie it to the lot you are shipped.
NovaFlex publishes a COA for every batch
Every lot is verified by HPLC and mass spectrometry, with the certificate tied to the compound you receive. US-based, $0 shipping over $199.
Browse the catalog → Receptor classes explained →For research use only — not for human or veterinary use. This guide describes how analytical documentation is produced and read for laboratory research materials. It is not guidance on the use of any compound.