How to Read a Certificate of Analysis: The Complete 2026 Guide
A Certificate of Analysis (COA) is the document that tells you what's actually in a peptide product. It's the single most important piece of information a buyer can review before making a purchase decision. But most people don't know how to read one — and that's exactly what bad actors count on.
This guide breaks down every section of a peptide COA, explains what the numbers mean, and teaches you how to spot the red flags that indicate a fake or unreliable certificate.
What Is a Certificate of Analysis?
A COA is a document issued by an analytical laboratory that reports the results of testing performed on a specific batch of a product. For peptides, a COA typically includes purity analysis (HPLC), identity confirmation (mass spectrometry), and may include additional tests like endotoxin screening or residual solvent analysis.
There are two types of COAs you'll encounter: manufacturer COAs (issued by the company that made the product) and independent COAs (issued by a third-party lab with no financial relationship to the manufacturer). Independent COAs are more trustworthy because they remove the conflict of interest.
Section 1: HPLC Purity
What it measures: The percentage of the target compound relative to all detected substances in the sample. Higher is better.
Method: Reversed-Phase HPLC (RP-HPLC) with UV detection, typically at 220nm wavelength using a C18 column.
What to look for:
| Purity | Grade | Assessment |
|---|---|---|
| 99%+ | Pharmaceutical grade | Exceptional purity. Rare in RUO peptides. |
| 98–99% | Research grade (high) | Very good. Standard for quality vendors. |
| 95–98% | Research grade (standard) | Acceptable for most research applications. |
| 90–95% | Low grade | Significant impurities. Caution warranted. |
| Below 90% | Substandard | Not suitable for research. Major quality concerns. |
The chromatogram: A good COA includes the actual HPLC chromatogram — a graph showing peaks at different retention times. The main peak represents your target compound. Smaller peaks represent impurities. You want one dominant peak and minimal noise.
Section 2: LC-MS Identity Confirmation
What it measures: Whether the compound is actually what it claims to be, by confirming its molecular weight.
Method: Liquid Chromatography-Mass Spectrometry (LC-MS or LC-MS/MS). The mass spectrometer measures the molecular weight of the compound.
What to look for: The observed molecular weight should match the theoretical molecular weight within ±1 Da (dalton). For example, Semaglutide has a theoretical MW of 4,113.58 Da. An observed value of 4,113.61 Da confirms identity. A value of 3,800 Da would mean it's a completely different compound.
This is the test that catches mislabeled compounds. HPLC only tells you purity — it doesn't confirm what the compound actually is. LC-MS is the identity check. If a COA doesn't include mass spectrometry data, you're trusting the label without verification.
Section 3: Net Peptide Content
What it measures: The actual amount of active peptide in the vial, as opposed to the total weight of the powder.
Why it matters: A vial labeled "10mg" contains 10mg of total powder — but that includes counterions (TFA or acetate salts), moisture, and residual solvents. The actual peptide content is typically 60–85% of the labeled weight.
What to look for: Net peptide content of 70–85% is normal. Below 60% suggests degradation or poor manufacturing. This test helps you calculate accurate dosing.
Section 4: Endotoxin Testing (LAL)
What it measures: Bacterial endotoxin levels using the Limulus Amebocyte Lysate (LAL) method.
Why it matters: Endotoxins are fragments of bacterial cell walls that can cause fever, inflammation, and serious adverse reactions when injected. Even "sterile" products can contain endotoxins.
Specification: Less than 0.50 EU/mg (Endotoxin Units per milligram) is the standard threshold. Results like "< 0.25 EU/mg" are excellent.
Section 5: Heavy Metals & Residual Solvents
Heavy metals (ICP-MS): Screens for lead, arsenic, cadmium, and mercury per ICH Q3D guidelines. These can accumulate in the body and cause long-term harm.
Residual solvents (GC-headspace): Checks for leftover manufacturing solvents like DMF, DCM, TFA, and acetonitrile per ICH Q3C guidelines. These should be below specified limits.
What to look for: "Conforms to ICH Q3D/Q3C" means all tested metals and solvents are within acceptable limits. If specific values are listed, check them against the ICH guidelines.
How to Spot a Fake COA
Red Flag: No chromatogram included
A legitimate COA always includes the actual HPLC chromatogram. If you only see a table of numbers with no supporting data, be suspicious. Numbers are easy to fabricate; chromatograms are harder to fake convincingly.
Red Flag: Round numbers everywhere
Real analytical results have decimal precision. A purity of "99.12%" looks real. A purity of "99.00%" looks suspiciously round. Real instruments produce messy, specific numbers.
Red Flag: No batch number or date
Every COA should reference a specific batch/lot number and testing date. If these are missing, the COA might be a generic template reused across multiple batches.
Red Flag: Manufacturer-issued with no independent verification
A COA from the same company selling you the product has an inherent conflict of interest. It's not necessarily fake, but it's not independently verified either. Look for third-party COAs from accredited laboratories.
Red Flag: No verification method
Modern COAs from reputable testing services include QR codes or verification links that let you confirm the certificate is real. If there's no way to verify the COA independently, you're trusting a PDF that anyone could have created.
The Gold Standard: What a Good COA Looks Like
A trustworthy COA includes all of the following: compound name and batch number, testing date and analyst name, testing laboratory and accreditation status, HPLC purity with chromatogram, LC-MS identity confirmation with observed molecular weight, additional tests as applicable (endotoxin, solvents, metals), and a verification method (QR code, verification URL, or database lookup).
KORECOA COAs include all of the above, plus a unique QR verification code that links to our public database. Anyone — buyer, vendor, regulator — can verify the authenticity of a KORECOA certificate in seconds at korecoa.com/verify.
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