GUIDES
You’ve just received a peptide vial, and somewhere in the packaging — or in your inbox — is a document called a Certificate of Analysis. Most researchers glance at it and move on. Learning to actually read it takes about five minutes, and it can save your entire experiment.
A Certificate of Analysis (COA) is a document produced by a third-party or in-house laboratory. It records the test results for a specific batch of a compound. Think of it like a report card — except instead of grades in maths, it shows chemical identity, purity, and batch information.
Every legitimate research peptide supplier should provide one. If they don’t, that alone is a red flag.
The COA connects directly to a specific lot number (a unique code identifying the exact production batch). Without a lot number, you have no way to know whether the results shown actually belong to your vial.
Here’s what to look for, field by field.
1. Lot Number
Find it near the top of the document. Cross-reference it with the number printed on your vial label. They must match. A COA without a lot number — or one that uses a generic placeholder — offers no real traceability.
2. Compound Name and Molecular Weight
The document should clearly state the peptide name and its molecular weight (the total mass of the molecule, measured in Daltons or g/mol). Compare this against a known reference value for that peptide. Even a small discrepancy can mean the substance is degraded, truncated, or simply wrong.
3. Purity Percentage (HPLC Result)
This number comes from a test called HPLC (High-Performance Liquid Chromatography — a method that separates a sample’s components to measure how much of it is the target compound versus impurities). A purity of 98% or above is the benchmark for research-grade material. You can read more about how this testing works in this guide to peptide purity testing: HPLC and mass spec standards.
4. HPLC Trace (Chromatogram)
A reputable COA doesn’t just show a percentage — it includes the actual chromatogram (a graph showing peaks that represent different chemical components in the sample). The main peak should be tall, clean, and clearly dominant. Multiple large peaks of similar height suggest a heavily contaminated sample.
5. Mass Spectrometry Confirmation
Mass spectrometry (MS) is a technique that measures the precise mass of molecules in a sample. It confirms identity — not just purity. A compound can score 98% purity on HPLC while still being the wrong molecule entirely. The MS result should show a measured mass that matches the expected molecular weight of your peptide. Missing mass spec data is a significant red flag.
“98% pure” means that 98% of the measurable content in the sample is your target peptide. The remaining 2% consists of impurities — fragments, solvents, or residual synthesis reagents.
For most research purposes, 98%+ is excellent. It means you’re working with a highly characterised substance and that your dosing calculations are reliable.
A purity of 95% isn’t disastrous, but it does mean more unknowns are present. Below 90%? That’s a compound you should question seriously before using in any research protocol.
Here’s a quick reference:
| Purity Level | Research Suitability | Notes |
|---|---|---|
| ≥ 98% | Excellent | Standard for quality research use |
| 95–97% | Acceptable | Minor impurities; note in protocol |
| 90–94% | Marginal | Increased unknowns; proceed cautiously |
| < 90% | Poor | High impurity load; not recommended |
Cross-checking identity is a two-step process.
Step 1 — Match the name. The compound name on the COA should match your order confirmation exactly. Watch for common naming variations. “BPC-157” and “Body Protection Compound 157” are the same thing — but “BPC-157 Acetate” has a slightly different molecular weight than the free-form version. Check which form you ordered.
Step 2 — Match the molecular weight. Look up the expected molecular weight of your peptide from a reliable chemical database. Compare it to what the mass spectrometry result shows. A match confirms identity. Even a difference of a few Daltons deserves investigation. For context, if you’re working with a complex molecule like Tirzepatide or Retatrutide, molecular weight verification is especially important given their structural complexity.
Run through this every time a new vial arrives:
Skipping the lot number check: A COA is only meaningful if it matches the specific batch in your hands — always verify the numbers align.
Accepting purity without the chromatogram: A percentage printed without a supporting graph is unverifiable — insist on seeing the actual trace.
Ignoring missing mass spec data: Purity alone doesn’t confirm identity — without mass spectrometry, you can’t be certain you have the right compound at all.
Not accounting for compound form: Acetate salt forms and free-base forms have different molecular weights — make sure your reference value matches the exact form listed on the COA.
Using an outdated COA: A test result from several years ago may not reflect the current batch — always request documentation specific to your order.
Q: Can I trust a COA from the supplier themselves?
Third-party testing is always more reliable than in-house testing, since it removes the conflict of interest. Look for a named external laboratory on the document.
Q: What if the supplier won’t provide a COA?
Don’t order. A supplier unwilling to share analytical data for their compounds is a significant quality concern, regardless of their pricing or marketing.
Q: Does a high purity percentage mean the peptide is stable?
Not necessarily. Purity reflects what the compound was at the time of testing — proper storage matters just as much. See this guide on lyophilised peptide storage, temperature, and shelf life for more.
Q: I’m using a reconstituted vial — does the COA still apply?
Yes. The COA covers the compound as supplied. Your reconstitution technique is a separate variable. A solid starting point is the BPC-157 vial reconstitution guide for reconstitution best practices.
Q: What’s the difference between HPLC purity and overall quality?
HPLC purity measures how much of the sample is the target compound. Overall quality also includes identity confirmation (mass spec), sterility, and endotoxin levels — a complete COA addresses all of these.
All products sold by biohacker.team are for research use only. They are not intended for human consumption or veterinary use, and are not intended to diagnose, treat, cure, or prevent any condition. Use is restricted to qualified researchers and in vitro testing environments. Not approved for human use.