A Certificate of Analysis is the most important document in the peptide supply chain. This guide teaches you how to interpret every section, spot red flags, and distinguish real COAs from fakes.
A Certificate of Analysis (COA) is a formal document that verifies the identity, purity, and quality of a specific batch of a compound. For research peptides, the COA confirms that what's in the vial matches what's on the label — and that it meets minimum quality standards for research use.
A proper COA answers four core questions: Is this the right compound? (identity), How pure is it? (purity), How much is actually in the vial? (content), and Is it free from harmful contaminants? (safety).
The top of every COA should include: compound name (e.g., Semaglutide), batch/lot number (unique to this production run), testing date, laboratory name, and analyst signature or ID. The batch number is critical — it should match the number on your vial. If it doesn't, the COA may not apply to your specific product.
High-Performance Liquid Chromatography (HPLC) is the gold standard for measuring peptide purity. The instrument separates the sample into components and measures how much of the total is your target peptide vs. impurities. Look for ≥98% for research-grade and ≥99% for high-purity applications. A quality COA includes the actual chromatogram image showing the peaks, not just a percentage number.
Mass spectrometry confirms molecular identity by measuring the exact molecular weight of your peptide. The COA will list both the theoretical (expected) mass and the observed (measured) mass. These should match within ±1 Da (dalton). A large discrepancy means you may have the wrong compound entirely. This is the test that confirms "this is actually Semaglutide" rather than just "this is 99% pure something."
This is one of the most misunderstood values on a COA. HPLC purity and net peptide content are NOT the same thing. A peptide can be 99% pure by HPLC but only have 70–80% net peptide content. That's because lyophilized peptides also contain water, salts (like TFA/acetate counterions), and other non-peptide material. Net peptide content tells you how much of the total weight in the vial is actual peptide — which directly affects dosing calculations in research.
AAA breaks down the peptide into its individual amino acids and quantifies each one. This confirms the correct sequence composition — verifying that the right amino acids are present in the right ratios. Not all COAs include AAA (it's typically in comprehensive packages), but it's especially valuable for custom or complex peptides.
For injectable compounds, endotoxin and sterility testing is critical. Bacterial endotoxin testing (LAL method) detects pyrogens that can cause severe immune reactions. Results are reported in EU/mg (endotoxin units per milligram) — lower is better, and <0.5 EU/mg is the typical threshold. Sterility testing confirms no bacterial or fungal contamination. Note: standard RUO COAs often don't include these tests unless specifically requested.
This section describes the peptide's appearance (e.g., "white lyophilized powder"), solubility (e.g., "soluble in sterile water"), and sometimes pH. While less analytical than the purity sections, physical properties help you confirm the product matches expectations. A peptide that should be a white powder but arrives as a yellow liquid is a clear warning sign.
| HPLC Purity | Grade | Suitable For |
|---|---|---|
| ≥99% | High Purity | Quantitative assays, structural biology, binding studies, cell work |
| 95–98% | Research Grade | Most discovery-phase research, screening, general use |
| 90–95% | Economy Grade | Preliminary studies, method development (use with caution) |
| <90% | Below Standard | Significant impurities may affect results — not recommended |
An in-house COA is generated by the manufacturer's own quality control lab. A third-party COA is issued by an independent laboratory with no financial stake in the product. Both can be valid, but third-party COAs carry significantly more credibility because they eliminate the inherent conflict of interest in a manufacturer testing their own products.
The most trustworthy suppliers provide both: initial in-house testing followed by independent third-party verification. This is exactly what KORECOA provides — independent Korean third-party COAs for compounds manufactured anywhere in the world.
Unfortunately, fake and misleading COAs are common in the peptide market. Here are the warning signs to look for:
Without a lot/batch number matching your vial, the COA could apply to any batch — or no batch at all.
Real HPLC results show decimal precision (e.g., 98.74%). A flat "99%" or "100%" suggests the number was fabricated.
A legitimate COA includes the actual HPLC chromatogram image. Text-only purity claims with no supporting data are suspect.
COAs that look identical across different peptides (same layout, same values) may be mass-produced fakes rather than batch-specific analyses.
Legitimate COAs name the testing laboratory, analyst, and often include accreditation information. Anonymous COAs are meaningless.
HPLC alone can't confirm identity — a wrong peptide could still show 99% purity on HPLC. Mass spectrometry is essential for identity confirmation.
A COA from 2+ years ago doesn't reflect current batch quality. Peptides degrade — request recent batch-specific testing.
Can you independently verify the COA? Reputable labs provide verification codes, portals, or direct contact methods. If there's no way to confirm authenticity, treat the COA with skepticism.
Every COA issued by KORECOA under the VerifyKorea standard includes: compound identity via LC-MS/MS, HPLC purity with chromatogram, batch-specific data, analyst identification, testing date, and a unique QR verification code that anyone can use to confirm authenticity through our online portal.
We built this verification system specifically because fake COAs are eroding trust in the peptide market. If a COA has a VerifyKorea code, it's real. If it doesn't scan, it's not ours.
Submit your peptide for independent third-party analysis. Get a verifiable Korean COA backed by accredited laboratory data.