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Certificates of Analysis
Every batch is independently third-party tested. Search our complete COA archive — .
How to Read & Verify a COA
A Certificate of Analysis is a batch-specific lab report. Read correctly, it’s one of the most powerful tools a researcher has. Read carelessly, it creates false confidence. Here’s how to read one like a scientist — not a shopper.
The “acceptable” thresholds on a COA are often set by the company selling the product.
For research compounds there is no single, legally mandated purity standard. A green “Pass” only means the material met that company’s own specification — which may be high, or may be low. Two vendors can both print “PASS”: one set purity at ≥99%, the other at ≥95%. Same word on the page, very different material in the vial.
Don’t take this lightly. Decide what “acceptable” means on every marker before you trust a verdict, and read the actual numbers — not the checkmark. This is for your own protection.
1Match the COA to your batchA COA describes exactly one lot. A great COA from a previous batch tells you nothing about the vial in your hand.Read more ↓▾
Every legitimate COA is tied to a specific lot / batch number, and that number must match the lot printed on the product you received. Look for a manufacture date and a test date. Quality can vary lot to lot, so a prior batch passing does not carry over. If a seller shows a generic COA, an older COA, or one whose lot doesn’t match your product, treat it as no COA at all.
2Purity by HPLC — what the % really meansThe headline “purity %” tells you how much was one main peak — not what the rest is, and not the peptide’s weight.Read more ↓▾
Purity is usually measured by reverse-phase HPLC and reported as area percent — the main peak as a fraction of all peaks detected by UV, typically around 214–220 nm. Its limits matter:
- Area% depends on the method (gradient, column, wavelength) — different methods give different numbers.
- Impurities that absorb weakly at the chosen wavelength can be under-counted.
- It does not identify what the impurities are.
- It is not weight purity, and ignores water, salts, and counterions.
Look for the actual number (98.4% vs 99.6% is a real difference), the method, and ideally the chromatogram. For research peptides ≥98% is common; ≥99% is premium. A number with no method and no chromatogram is a weaker claim.
3Identity by Mass Spec — is it the right molecule?HPLC tells you how much of one thing is present. Mass spec tells you whether that thing is actually the right compound. You want both.Read more ↓▾
Mass spectrometry (commonly ESI-MS or MALDI-TOF) confirms the molecular weight of the main component matches the expected weight of the target. A sample can be highly “pure” by HPLC yet be a pure wrong molecule if identity was never confirmed. Look for observed vs. theoretical mass and the method used; sequence confirmation (MS/MS) is stronger still. Purity with no identity testing is only half the picture.
4Net peptide content — 99% pure ≠ 99% peptideA freeze-dried peptide is not pure peptide by weight. It also holds water and salts.Read more ↓▾
Lyophilized peptides carry water, counterions, and residual salts. The net peptide content assay tells you what fraction of the powder’s mass is truly peptide — frequently 70–90%. So a vial can read 99% pure by HPLC and still be only ~80% peptide by mass. If you quantify by weight, this is critical. Many COAs omit net peptide content — and that omission is itself a gap.
5Water, counterions & residual solventsExtra water or leftover solvent means less compound per milligram and can affect stability and sensitive assays.Read more ↓▾
- Water content (Karl Fischer): peptides are often hygroscopic; more water = less peptide per mg and faster degradation.
- Counterion (TFA vs. acetate): TFA residue can interfere with certain sensitive assays; acetate is often preferred. A thorough COA states the counterion and its %.
- Residual solvents: traces from purification (e.g., acetonitrile) should fall within recognized limits if reported.
6Safety markers — endotoxin, heavy metals, microbialThese matter more for some research than others. Know whether they were done — and whether your work needs them.Read more ↓▾
- Endotoxin (LAL test): relevant for cell-culture and in-vivo research; reported in EU/mg. Often absent from basic research-use COAs.
- Heavy metals, microbial / bioburden, sterility: depend on the research context and are often not performed for bench chemicals.
Honest note: the absence of these tests isn’t automatically “bad” for pure bench work — but you should know they weren’t performed and decide whether your application requires them.
7Who set the thresholds? Read the “spec” columnNext to each result is a “specification” — the range that counts as passing. Ask who chose it. Often, it’s the seller.Read more ↓▾
A pass/fail verdict is only as meaningful as the specification behind it — and for research compounds that spec is commonly set by the manufacturer or vendor themselves. Read the specification column, not just the result. Set your own benchmark — for example: HPLC purity ≥99%, identity confirmed by MS, net peptide content reported, tested by a named independent lab — and hold every COA to your standard, regardless of whose checkmark is on it.
8In-house vs. independent third-party testingTesting by an outside, accredited lab is more trustworthy than a seller grading its own homework.Read more ↓▾
In-house testing means the seller tested its own product — a real conflict of interest. Independent third-party testing by an outside laboratory removes that conflict. Look for the lab’s name, an accreditation (such as ISO/IEC 17025), a method reference, and ideally an analyst signature. A COA with no named lab, method, or signature is weak evidence no matter how good the numbers look.
9How to verify a COA is authenticA nice-looking PDF is not proof. Confirm it’s real and that it matches your product.Read more ↓▾
- Does the lot number match the vial you received?
- Is there a manufacture and test date?
- Is the testing laboratory named and reachable?
- Are the methods stated (HPLC conditions, MS type)?
- Is there an analyst / signature?
- Can you cross-check the lot with the vendor or testing lab?
Be cautious of PDFs with no lab identity, mismatched or missing lot numbers, or figures with no supporting method or chromatogram.
✓ A strong COA has
- Lot number matching your product
- Manufacture & analysis dates
- HPLC purity with method and chromatogram
- Identity confirmed by MS
- Net peptide content
- Water content & counterion
- A named, independent, accredited lab
- Specifications visible by each result
- Analyst / signature
⚑ Red flags
- A generic/old COA that doesn’t match your lot
- “Pass” or a checkmark with no numbers
- Purity with no method or chromatogram
- No identity (MS) testing at all
- No named laboratory, method, or signature
- Specifications hidden — only a verdict shown
- Marketing claims (“99%+”) with no document
A final, honest word. A COA is a tool, not a guarantee. It documents what was tested, on one batch, against a stated specification — no more and no less. It does not certify safety, biological activity, or suitability for any particular use. Interpretation and any resulting research decision are the responsibility of the researcher. Understand what each marker means, know what “acceptable” looks like to you, and hold every certificate — including ours — to that standard.