How to Read a Certificate of Analysis (COA) for Peptides
Written by Alejandro Reyes
Founder & Lead Researcher
Reviewed by Peptide Nerds Editorial · Updated March 2026
How to Read a Certificate of Analysis (COA) for Peptides
Fake COAs are more common than most buyers realize. Here is how to tell the difference between a legitimate certificate of analysis and one that was made in Photoshop.
Key takeaways:
- A COA is a lab document that tells you the purity, identity, and quality of a specific peptide batch
- HPLC purity above 98% is considered high quality. Below 95% is a red flag
- Mass spectrometry confirms the compound is actually what the label says it is
- Third-party testing (independent lab) is the gold standard. In-house testing has a built-in conflict of interest
- Fake COAs exist. Knowing the red flags can save you from wasting money on contaminated or misidentified compounds
Important: This is not medical advice. The information below is for educational purposes only. Research peptides are not FDA-approved for human use. Always consult a qualified healthcare provider. See our full medical disclaimer.
What a COA is and why it matters
A Certificate of Analysis is a document issued by a laboratory after testing a specific batch of a compound. It reports what the compound is, how pure it is, and whether it meets quality standards.
For research peptides, a COA is the only way to verify what is actually in the vial. Unlike FDA-approved pharmaceuticals that go through rigorous manufacturing oversight, research peptides operate in a space with far less regulation. The COA is the closest thing to a quality guarantee you will find.
Without a COA, you are trusting a vendor's word that the powder in your vial is what they say it is, at the purity they claim. That is not a position you want to be in when dealing with compounds that interact with biological systems. For more on what to watch for, see our guide on peptide vendor red flags.
The key sections of a COA
Not all COAs look the same, but legitimate ones share the same core data points. Here is what to look for and what each section means.
HPLC purity percentage
HPLC stands for High-Performance Liquid Chromatography. This is the primary test for peptide purity. It separates the components of a sample and measures what percentage of the total is the target peptide versus impurities.
How to read the number:
| Purity Range | What It Means |
|---|---|
| 98% and above | High quality. This is what reputable vendors typically deliver |
| 95% to 98% | Acceptable for most research purposes. Common for more complex peptides |
| Below 95% | Red flag. Higher impurity content. Question the vendor |
| Not listed | Major red flag. A legitimate COA always includes HPLC data |
The HPLC result should include a chromatogram, which is a graph showing the peaks detected during analysis. The main peak represents the target peptide. Smaller peaks represent impurities. A clean chromatogram has one dominant peak with minimal noise.
Mass spectrometry (molecular weight confirmation)
Mass spectrometry (MS) identifies a compound by measuring its molecular weight. Every peptide has a known molecular weight based on its amino acid sequence. The mass spec result on a COA should match the published molecular weight of the compound.
This is the identity test. HPLC tells you how pure the sample is. Mass spec tells you whether the sample is actually the right compound.
If the molecular weight on the COA does not match the known molecular weight for that peptide, something is wrong. Either the peptide was synthesized incorrectly, or the COA does not belong to the product in your hand. For example, BPC-157 has a known molecular weight of 1419.53 Da and TB-500 comes in at 4963.44 Da. Any significant deviation from published values is cause for concern.
Batch/lot number
Every COA should reference a specific batch or lot number. This ties the test results to a specific production run.
Why it matters: a vendor might have one batch tested at 99% purity and another at 93%. The batch number lets you verify that the COA you are looking at actually corresponds to the product you received. Check the lot number on the COA against the lot number on your product label. They should match.
Date of analysis
The COA should show when the testing was performed. This date should be reasonably close to the production or distribution date of the batch. A COA from two years ago attached to a product shipped yesterday raises questions about whether the current batch was actually tested.
Laboratory name and contact information
A real COA comes from a real lab. The document should include the name of the laboratory, its address, phone number or email, and ideally a signature or stamp from the analyst or quality assurance officer.
If the COA does not name the lab, you cannot verify the results. That alone makes the document unreliable.
In-house testing vs third-party testing
This is the single most important distinction when evaluating COAs. Not all testing is created equal.
In-house testing
In-house testing means the vendor tested their own product in their own lab (or a lab they control). This is better than no testing at all, but it has an obvious limitation: the vendor has a financial incentive to report favorable results. There is a built-in conflict of interest.
Many vendors do conduct honest in-house testing. But you have no way to independently verify that from the document alone.
Third-party testing
Third-party testing means an independent laboratory, one with no financial relationship to the vendor, tested the product. The lab has no incentive to inflate purity numbers or overlook problems.
This is the gold standard.
The most well-known independent testing lab in the peptide research community is Janoshik Analytical, a Czech Republic-based lab that specializes in testing research compounds. They have built a reputation for transparent, batch-specific testing that researchers can verify directly with the lab.
Third-party testing removes the conflict of interest entirely. When a vendor pays an independent lab to test their product and publishes the results publicly, that is a strong signal of confidence in their product quality.
How to tell the difference
Look at the lab name on the COA. If it matches the vendor's company name, it is in-house testing. If it is a separate entity (especially a recognized analytical lab), it is third-party testing. Some vendors publish both: their own in-house results alongside independent third-party verification.
Red flags on fake or misleading COAs
Fake COAs exist. Some vendors create documents that look official but contain fabricated data. Here is how to spot them.
No lab name or contact information. A legitimate testing lab puts their name on their work. If the COA does not identify who performed the analysis, treat the entire document as unverifiable.
Generic template with no batch-specific data. Some vendors use the same COA for every batch, changing only the product name. Real testing produces unique data for each batch. If every product from a vendor has an identical-looking COA with suspiciously similar numbers, that is a problem.
Purity is always exactly 99.9%. Peptide synthesis is a chemical process with natural variation. A vendor reporting 99.9% purity across every single product, batch after batch, is statistically implausible. Real purity numbers vary. Seeing 98.7% on one batch and 99.2% on another is actually more credible than seeing 99.9% every time.
PDF metadata from a graphics program. This one requires checking the file properties of the COA PDF. If the metadata shows it was created in Canva, Photoshop, or another consumer design tool rather than laboratory software or a standard document editor, the document was likely fabricated.
No molecular weight or mass spec data. A COA that reports only purity without mass spectrometry data is incomplete at best. Without mass spec, you have no confirmation that the compound is what it claims to be. It could be 99% pure and still be the wrong peptide.
Dates that do not match your batch. If the analysis date on the COA is months or years before your batch was produced, the results may not apply to the product you received. Ask the vendor for batch-specific documentation.
How to verify a COA yourself
You do not need a chemistry degree to do basic verification. Here are practical steps anyone can take.
Cross-reference the lab name. Search for the laboratory online. Does it have a website? A physical address? Published methodology? If you cannot find any evidence that the lab exists outside of the COA, that is a problem.
Contact the lab directly. Most legitimate analytical labs will confirm whether they tested a specific batch if you provide the lot number. This is the most definitive verification step you can take. If the lab says they have no record of that batch, the COA is fraudulent.
Compare molecular weights. Look up the known molecular weight of the peptide (PubChem, UniProt, or the manufacturer's product page are all reliable sources). Compare it to what the COA reports. They should match. Small decimal differences are normal due to measurement precision. A large discrepancy means something is wrong.
Check publishing consistency. Does the vendor publish COAs for every batch of every product? Or do they only show COAs for select products? Vendors who publish batch-specific COAs across their entire catalog are demonstrating a commitment to transparency. Cherry-picked COAs raise questions about what the untested batches look like.
Community testing resources
Independent testing initiatives have emerged within the research community to provide additional verification beyond what vendors offer.
Finnrick Analytics has tested over 5,600 samples from nearly 180 vendors, building a database of real-world purity results across the research peptide market. Their data provides a useful reference point for comparing vendor claims against independent test results. We mention them as a resource, not an endorsement. Do your own due diligence.
Community-driven testing databases are valuable because they aggregate results across many batches and many vendors over time. A single COA tells you about one batch. Aggregated testing data tells you about a vendor's consistency.
Bottom line
A COA is the minimum standard of accountability for any research peptide vendor. Learning to read one takes five minutes. Learning to verify one takes another five.
The key things to check: HPLC purity (above 98% ideal, below 95% is a red flag), mass spectrometry (confirms identity), batch number (matches your product), lab name (real and verifiable), and whether the testing was done by an independent third party.
Do not take any COA at face value. Verify the lab. Check the batch number. Compare the molecular weight. The vendors with nothing to hide make this easy. The ones who make it difficult are telling you something.
For more on evaluating vendor quality, read our guide to peptide vendor red flags.
Frequently asked questions
What does HPLC stand for on a COA?
HPLC stands for High-Performance Liquid Chromatography. It is the standard method for measuring peptide purity. The test separates a sample into its components and reports what percentage is the target peptide versus impurities.
How do I verify a peptide COA is real?
The most reliable method is to contact the lab listed on the COA and ask them to confirm the batch number. You can also cross-reference the molecular weight against published databases like PubChem, and check the PDF metadata to see if it was created in lab software or a graphics editor.
What purity percentage is good for peptides?
HPLC purity of 98% or above is considered high quality. Anything between 95% and 98% is generally acceptable for research. Below 95% raises questions about synthesis quality or storage conditions. If no purity data is listed at all, treat that as a red flag.
What is third-party testing for peptides?
Third-party testing means an independent laboratory, one with no financial relationship to the vendor, performed the analysis. This removes the conflict of interest that exists when vendors test their own products. It is the most reliable form of COA verification available. For a deeper look at safety considerations, see our peptide safety guide.
This article is for educational purposes only and is not medical advice. Research peptides discussed here are not FDA-approved for human use. Always consult a qualified healthcare provider. See our full medical disclaimer.
Sources
- International Council for Harmonisation (ICH) Q6B, Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products
- United States Pharmacopeia (USP) General Chapter 621, Chromatography
- European Pharmacopoeia 2.2.29, Liquid Chromatography
- PubChem Compound Database, National Center for Biotechnology Information (NCBI)
- Janoshik Analytical, Independent Peptide and SARM Testing Laboratory (janoshik.com)
- Finnrick Analytics, Independent Peptide Testing Database (finnrick.com)
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