A Certificate of Analysis (COA) is the primary quality assurance document for research peptides. It reports the results of analytical testing performed on a batch of compound, including purity by HPLC, identity confirmation by mass spectrometry, and any other quality parameters the lab tests. Not all COAs are equal — some are rigorous third-party analyses, others are lab-generated documents that may be incomplete, outdated, or fabricated. Knowing how to interpret and verify a COA is essential for responsible research peptide sourcing.
Research context only. The peptides discussed on WolveStack are research chemicals not approved for human use by the FDA. Nothing on this page constitutes medical advice. Consult a qualified healthcare professional before use.
A complete guide to reading and verifying peptide Certificates of Analysis. What HPLC purity means, mass spec verification, what red flags look like, and how to spot fake COAs.
HPLC Purity: The Key Number
HPLC (High-Performance Liquid Chromatography) purity is the most important number on a peptide COA. It measures what percentage of the compound in a sample is the target peptide (versus degradation products, synthesis impurities, residual solvents, or other peptides). A legitimate research-grade peptide should have HPLC purity ≥98%. Values between 95–97% are acceptable but worth noting. Anything below 95% should raise concerns, and below 90% is generally considered sub-pharmaceutical quality for research purposes.
HPLC works by separating components of a solution based on their differential affinity for a stationary phase, producing a chromatogram with peaks corresponding to each component. The target peptide's peak area divided by total peak area gives the purity percentage. A high-quality COA includes the actual chromatogram — a visual graph of the separation — not just the purity number. COAs that list purity without including the chromatogram are less verifiable.
Mass Spectrometry: Identity Verification
While HPLC tells you how pure the compound is, it cannot tell you what that compound actually is — a sample could be 99% pure of the wrong peptide. Mass spectrometry (MS or LCMS) confirms molecular identity by ionising the compound and measuring the mass-to-charge ratio of the resulting ions. The measured molecular weight is then compared to the theoretical molecular weight of the target peptide. A match (within ±0.5 Da typically) confirms the compound is what it claims to be.
A complete quality COA should include both HPLC purity AND mass spectrometry confirmation. A COA with only HPLC but no mass spec is incomplete — it confirms purity but not identity. High-quality vendors like Ascension Peptides provide both and publish them by lot number so you can match your vial to its specific batch data.
Third-Party vs. In-House Testing
The most trustworthy COAs are from independent third-party laboratories with no financial relationship to the vendor — the lab is paid to test objectively, not to approve product. Third-party labs used in the US include Janoshik Analytical, Colmaric Analyticals, and Lab4Tox. A COA referencing one of these labs with a verifiable batch number is significantly more credible than a vendor's own in-house testing.
Red flags suggesting in-house or fabricated COAs: the lab name is not independently verifiable, there is no batch/lot number, the date is not recent (a COA from 2021 applied to a 2024 batch is meaningless), purity is suspiciously round (exactly 99.00% is uncommon in legitimate testing), or the format looks like a Word document template rather than a professional lab report. Some vendors encourage customers to request COAs by lot number — if the vendor cannot provide the COA for your specific lot, that is a concern.
Other Parameters in a COA
Beyond purity and identity, quality COAs may include: water content (Karl Fischer titration) — important because lyophilised peptides absorb moisture and excess water means you're getting less actual peptide per milligram than labelled; amino acid analysis — confirms peptide composition; endotoxin testing (LAL test) — checks for bacterial endotoxins that cause pyrogenic reactions; and residual solvent analysis — confirms safe levels of synthesis solvents. Not all COAs include all parameters, but water content and endotoxin testing are valuable indicators of a thorough quality program.
COA Quality Checklist
| Parameter | Dose | Route | Frequency | Notes |
|---|---|---|---|---|
| HPLC Purity | ≥98% | Core quality metric | Chromatogram should be included | Essential |
| Mass Spec (LCMS) | Matches theoretical MW ±0.5 Da | Identity confirmation | Without this, identity is unverified | Essential |
| Third-party lab | Independent lab with verifiable name | Testing objectivity | Janoshik, Colmaric, Lab4Tox are common | Strongly recommended |
| Lot number / date | Must match your purchase batch | Document validity | Old COAs applied to new batches are invalid | Essential |
| Water content | <10% typical | Actual peptide dose accuracy | High water content means less active peptide | Bonus |
Also Available at Apollo Peptide Sciences
Apollo Peptide Sciences carries independently tested research-grade compounds. Products ship from the USA with published purity certificates.
For research purposes only. Affiliate disclosure: WolveStack earns a commission on qualifying purchases at no additional cost to you.
Frequently Asked Questions
Generally ≥98% is the benchmark for pharmaceutical-research-grade quality. Values of 95–97% are common and acceptable for most applications. Below 95% is substandard for research use. Some applications (receptor binding studies, for example) require ≥99%.
You can verify several aspects: check the lab name is a real independent lab (searchable online); verify the molecular weight on the mass spec matches published values for that peptide; check the date is consistent with a current batch. To truly verify HPLC data requires analytical training. The most practical approach is purchasing from vendors who use well-known third-party labs (Janoshik, Colmaric) and who provide COAs by batch number.
HPLC purity does not confirm what the compound actually is — a 99% pure sample of the wrong peptide would pass HPLC purity testing. This is why mass spectrometry identity confirmation is equally important. HPLC also does not detect endotoxins, confirm water content, or reveal all possible impurities depending on the analytical method used.
The lot/batch number on the COA should match the lot number on the vial label or documentation provided at purchase. Quality vendors include lot numbers on vials and publish COAs searchable by lot number. If your vendor cannot provide a COA for your specific lot number, request one before using the compound.
In-house vendor COAs should be viewed with more skepticism than independent third-party COAs. This does not mean they are falsified — many vendors conduct legitimate in-house QC — but they lack the objectivity of independent testing. Third-party COAs from named, verifiable labs are the gold standard. When evaluating a vendor, prioritising those who publish third-party COAs by lot number is the most reliable quality signal.