How to Read a Peptide Certificate of Analysis
A Certificate of Analysis (CoA) is the single most important document that ships with a research peptide. It is the record of what an analytical laboratory measured for one specific batch — and it is the only way to confirm that the material on your bench matches what you ordered.
This guide walks through every field you will find on a typical peptide CoA, explains what each measurement means, and shows how to tell a rigorous CoA from a weak or decorative one.
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What a Certificate of Analysis actually is
A CoA is a signed analytical report tied to a single production lot. It is not a marketing document and it is not generic — a genuine CoA describes one batch, identified by a lot number, tested on a specific date. If a supplier shows the same CoA for every order of a product, that is a red flag.
The most trustworthy CoAs are produced by an independent, third-party laboratory with no commercial stake in the sale. Third-party testing removes the conflict of interest that exists when a vendor grades its own material.
The fields on a peptide CoA
Most peptide CoAs contain the same core fields. Here is what each one tells you.
Product name and lot number
The lot (or batch) number is the anchor of the whole document. It must match the number printed on your vial. If the vial and the CoA carry different lot numbers, the document does not describe your material.
HPLC purity
High-Performance Liquid Chromatography separates the target peptide from impurities and reports purity as a percentage — for research-grade material this is typically 98–99%+. A good CoA includes the actual chromatogram: a trace with a dominant main peak and minimal smaller peaks. A purity number with no chromatogram attached is much weaker evidence.
Mass spectrometry (identity)
HPLC tells you how pure the sample is; it does not tell you what the sample is. Mass spectrometry confirms identity by measuring molecular weight. The observed mass should match the theoretical mass of the target peptide within a small tolerance. Purity without an identity check is only half the picture.
Appearance and net peptide content
Appearance describes the physical form — usually a white lyophilized powder. Net peptide content (or peptide loading) states how much of the vial's contents is actually peptide versus residual salts and water; it is often lower than the gross fill weight and matters for accurate study design.
Endotoxin / LAL and sterility
Endotoxin testing (the LAL assay) screens for bacterial toxins, reported in endotoxin units per milligram (EU/mg). Lower is better. For sensitive cell-culture work, contamination is a major source of unreliable data, so a CoA that includes endotoxin and sterility results is doing more for you than one that does not.
Water content and date of analysis
Residual water (often by Karl Fischer titration) affects stability. The date of analysis tells you how recently the lot was characterised.
How to spot a weak or fake CoA
- No lab named. A CoA with no issuing laboratory cannot be verified.
- Numbers but no graphs. "99% pure" with no chromatogram and no mass-spec spectrum is an assertion, not evidence.
- One CoA for all lots. A genuine CoA is lot-specific. A single recycled document is a warning sign.
- Mismatched lot numbers. If the vial and CoA disagree, the document is meaningless for your material.
- Identity missing entirely. Purity alone does not confirm the peptide is the one you ordered.
Matching the CoA to your vial
When an order arrives, take one minute to cross-check: confirm the lot number on the vial matches the CoA, confirm the product name and quantity match your order, and confirm the purity and identity results meet the specification you expected. This habit catches mislabelling and shipping errors before they reach your data.
How to verify a lot number
Matching the numbers is step one. Verifying means checking that the certificate itself is genuine. It takes about two minutes:
- Read the lot (batch) number on the vial label. It is usually printed next to the product name and the amount.
- Find the same number on the certificate. It must match character for character. A certificate for another lot, even of the same product, says nothing about your vial.
- Look the certificate up with the laboratory or testing service that issued it. Most print a verification code or a QR code. Janoshik reports carry a unique key you can check at janoshik.com/verify. Veritalys reports carry a VT- report number you can look up at veritalys.com/verify. If the record there differs from the document you were given, the document has been altered.
- Check the dates and the details. The analysis should be dated before your vial was shipped, and the certificate should name the product and the amount you ordered.
If any step fails, ask the supplier for the certificate of your lot before you use the material for work that matters.
At RetaNord, the batch number on every vial matches its certificate on the certificates page. Current reports from Veritalys carry a VT- report number, so you can check them yourself at veritalys.com/verify. For Retatrutide, Tirzepatide, Semaglutide and KLOW, that one record lists all 7 tests of the full panel.
How RetaNord documents every batch
Every RetaNord order ships with a lot-specific Certificate of Analysis, tested through Veritalys (an EU peptide testing service), that includes HPLC purity, identity confirmation by HPLC against a reference standard, and the lot number printed on the vial. Each batch is verified at 99%+ identity purity before it is released. You can read more about the testing process on the quality page.
Frequently asked questions
What is the difference between purity and identity on a CoA?
Purity (measured by HPLC) tells you what proportion of the sample is the target compound versus impurities. Identity (measured by mass spectrometry) confirms the sample actually is the peptide you ordered. A complete CoA reports both.
Should a peptide CoA come from a third-party lab?
Independent third-party testing is the strongest form of CoA because the testing laboratory has no commercial stake in the sale. It removes the conflict of interest present when a vendor grades its own material.
What does EU/mg mean on a CoA?
EU/mg is endotoxin units per milligram, the result of the LAL endotoxin assay. It measures bacterial toxin contamination — a lower value is better, and it matters most for sensitive cell-culture research.