A Certificate of Analysis (COA) is only useful if you know how to read one. Many suppliers post documents that look official but lack the data needed to actually verify product quality. This guide explains what each section means, what to look for, and what’s missing from low-quality COAs.
Why Verification Matters
Peptide purity directly affects experimental outcomes. A study comparing labeled vs. actual peptide content across multiple suppliers found purity ranging from 47% to over 99% for products all claiming ≥98%[1]. The difference isn’t academic – lower purity means your effective dose is wrong, contaminants may have their own biological activity, and results become irreproducible.
The Two Core Tests
HPLC (High-Performance Liquid Chromatography)
HPLC separates the components of your peptide sample by how they interact with a chromatography column. The output is a chromatogram – a graph with peaks.
What to look for:
- One dominant peak – this is your target peptide
- Peak purity >98% – the area of the main peak as a percentage of total peak area
- Small satellite peaks – these are impurities (truncated sequences, deletion mutants, residual solvents)
- Retention time – should be consistent across batches of the same peptide
Red flags:
- Multiple large peaks (significant impurities)
- A broad, diffuse main peak (poor separation – the test itself may be inadequate)
- No chromatogram shown at all (only a percentage claim)
Mass Spectrometry (MS)
MS confirms the molecular identity of your peptide by measuring its molecular weight. Every peptide has a specific expected mass.
What to look for:
- Observed mass matches expected mass – for example, BPC-157 should show ~1,419.5 Da
- Clear signal – a sharp peak at the expected mass
- Minimal noise – low-intensity peaks at other masses indicate contaminants
Why both tests matter:
- HPLC tells you how pure it is
- MS tells you what it actually is
- A sample could be 99% pure but be the wrong compound entirely. MS catches this.
Reading a COA: Section by Section
1. Header Information
Should include:
- Lab name and accreditation – look for ISO 17025
- Test date – recent tests are more meaningful than old ones
- Report number – unique identifier for verification
- Client/supplier name – confirms who commissioned the test
2. Sample Identification
Should include:
- Product name – matches what you received
- Batch/lot number – matches the batch you’re evaluating
- Appearance – typically “white to off-white lyophilized powder”
- Molecular weight – confirms identity
3. Test Results
Should include:
- Purity by HPLC – with the actual chromatogram
- Identity by MS – with the actual spectrum
- Specific test conditions – column type, mobile phase, detection wavelength
4. Verification
The strongest COAs include a way to verify the results independently:
- A verification link to the testing lab’s portal
- A QR code or verification key
- The lab’s direct contact information
In-House vs. Third-Party COAs
In-House COAs
These are generated by the supplier’s own lab. Problems:
- No independent verification – the supplier is grading their own homework
- Incentive to present favorable results
- No way to confirm the data is real
- Methods may not be validated
Third-Party COAs
Generated by an independent laboratory. Advantages:
- No financial conflict of interest
- Accredited labs have validated methods (ISO 17025)
- Results can often be verified at the lab’s portal
- More trustworthy for publication and documentation
The gold standard: Third-party COAs with public verification links. Janoshik Analytical is the most widely used independent lab in the research peptide space. Their portal at verify.janoshik.com allows anyone to look up test results by verification key.
Common COA Red Flags
- No lab name – if you can’t identify who did the testing, the COA is meaningless
- No batch number – the COA can’t be matched to a specific product
- No chromatogram – a purity percentage without the supporting data is just a claim
- Stock photo COAs – some suppliers use the same COA image for every batch
- Very old test dates – peptides degrade over time. A COA from 2 years ago may not reflect current product
- Missing MS data – purity without identity confirmation is incomplete
Verifying Your Specific Product
When you receive a peptide, here’s a verification checklist:
For example, Chameleon Peptides provides a Janoshik verification key with each product. Entering it at verify.janoshik.com pulls up the original test report with full HPLC and MS data, confirming both purity and identity.
What Purity Levels Mean in Practice
| Purity | Typical Use | Implications |
|---|---|---|
| ≥99% | Sensitive bioassays, quantitative work | Gold standard – minimal confounding from impurities |
| 95-98% | General in vitro research | Acceptable for most applications |
| 90-95% | Non-critical screening | Impurities may affect some sensitive assays |
| <90% | Generally not suitable for research | High impurity fraction, unreliable dosing |
For most research applications, ≥98% purity with independent verification is the appropriate standard.
References
[1]: Anal Bioanal Chem. 2019;411(25):6657-6670. Related analysis of peptide product quality variance across suppliers.
This article is for informational purposes only. Research peptides are sold for in vitro and preclinical research use only – not for human consumption or clinical use.