If you are injecting research-grade peptides without verifying the Certificate of Analysis, you are trusting the vendor’s marketing copy with your biology. A COA is the only document that stands between you and a vial of unknown purity, and most guys in the peptide space either skip it entirely or glance at a number without understanding what they are looking at. This is how people inject truncated sequences, bacterial endotoxins, or peptides with 85% purity when they paid for 99%.
⚡ Key Takeaway
A legitimate COA shows purity at or above 98% via HPLC, mass spectrometry confirming molecular weight, and comes from an independent third-party lab — not the vendor's in-house testing. If a vendor cannot produce a COA, or the COA lacks these elements, walk away.
What a COA Must Include
HPLC purity. High-Performance Liquid Chromatography is the standard method for measuring peptide purity. It separates the target peptide from impurities and reports the proportion of the sample that is the actual intended compound. You want to see 98% or higher. Below 95% is unacceptable for any research application. Between 95-98% is marginal — the impurities may include truncated sequences (incomplete peptide chains), oxidized variants, or synthesis byproducts.
Mass spectrometry. MS (typically ESI-MS or MALDI-TOF) confirms the molecular weight of the peptide. This is how you verify the compound is actually what the label says. HPLC tells you how pure the sample is; mass spectrometry tells you what the sample actually is. Both are required. A COA with HPLC but no MS data is incomplete.
Third-party lab identification. The COA should identify the testing laboratory by name, with a report number and date. The lab should be independent from the vendor — not an in-house facility. If the vendor’s COA has no lab name, or the lab name matches the vendor name, the testing is not independent and the results are unverifiable.
Batch/lot number. The COA should reference a specific production batch that matches the batch on your product. A generic COA without a batch number means the testing may not correspond to the actual product you received.
Red Flags That Should Kill the Purchase
No COA available. If a vendor cannot produce a COA for the specific product you are considering, there is no reason to believe the product contains what they claim. Walk away.
In-house testing only. Vendors who test their own products without independent verification have an obvious conflict of interest. Their COA is marketing material, not quality assurance.
Purity below 95%. Legitimate peptide synthesis routinely achieves 98%+ purity. Selling product below 95% suggests either poor synthesis, degraded product, or intentional dilution.
Missing mass spectrometry. HPLC alone confirms purity but not identity. Without MS data, you cannot verify the compound is the intended peptide rather than a different molecule that happens to elute at a similar retention time.
Undated or generic COAs. A COA without a date, or one that appears identical across multiple products or batches, suggests a template document rather than actual per-batch testing.
How to Verify a COA
The gold standard is sending a sample to an independent lab for third-party verification. Services like Janoshik Analytical and others in the research peptide space offer testing for a reasonable fee. This is expensive if you do it for every purchase, but doing it once with a new vendor establishes whether their COAs match reality.
Short of independent testing, cross-reference the COA lab name against known analytical laboratories. Check if the lab exists independently, has a website, and performs the type of testing listed on the COA. Contact the lab if possible to verify the report number corresponds to a real test.