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How to Read a Certificate of Analysis (COA) for Peptides

April 12, 20264 min readTruPeptide Editorial

What Is a Certificate of Analysis?

A Certificate of Analysis (COA) is a document issued by a laboratory that reports the results of testing performed on a specific batch of a product. For peptides, a COA typically includes purity analysis, identity confirmation, and sometimes sterility and endotoxin testing.

A legitimate COA is the single most important tool you have for verifying that a peptide product contains what it claims to contain, at the purity level advertised.

Key Components of a Peptide COA

1. HPLC Purity Analysis

High-Performance Liquid Chromatography (HPLC) is the standard method for measuring peptide purity. On a COA, look for:

  • Purity percentage: This should typically be 95% or higher for research-grade peptides, and 98%+ for pharmaceutical-grade. Anything below 95% is a red flag.
  • Chromatogram graph: A legitimate COA should include the actual HPLC chromatogram — a graph showing peaks. The main peak represents your peptide; smaller peaks represent impurities. If you only see a number with no graph, be skeptical.
  • Retention time: The time at which the peptide elutes from the column. This should be consistent with known values for that compound.

2. Mass Spectrometry (MS) Confirmation

Mass spectrometry confirms the molecular identity of the peptide by measuring its molecular weight.

  • Observed molecular weight should match the theoretical molecular weight for the compound (within a small margin of error).
  • If the observed MW doesn't match, the product may not be what it claims to be — regardless of what the HPLC purity says.
  • This is how mislabeled products get caught. A vial labeled "BPC-157" with the molecular weight of GHRP-2 is not BPC-157.

3. Batch/Lot Number

  • Every COA should reference a specific batch or lot number.
  • This number should match the label on your product.
  • If a vendor provides a "generic" COA without a batch number, it's likely not testing your specific product.

4. Testing Laboratory

  • Third-party testing is the gold standard. The COA should be from an independent lab, not the vendor's own facility.
  • Well-known independent labs in the peptide space include Janoshik Analytical, MZ Biolabs, and Colmaric Analyticals.
  • If the lab name is missing or unfamiliar, try to verify it exists independently.

5. Date of Analysis

  • The COA should have a recent date. A COA from 2019 doesn't tell you anything about a product manufactured in 2026.
  • Ideally, the testing date should be within 12 months of your purchase.

Optional But Valuable: Sterility and Endotoxin Testing

For injectable peptides, these additional tests matter:

  • Sterility testing: Confirms the product is free from microbial contamination.
  • Endotoxin testing (LAL test): Measures bacterial endotoxin levels. High endotoxin levels in injectable products can cause fever, inflammation, and serious adverse reactions.

Not all COAs include these, but for injectable products, they significantly increase confidence in product safety.

Red Flags: How to Spot a Fake COA

  • No chromatogram graph — just a purity number with no supporting data.
  • No batch number — or a batch number that doesn't match your product.
  • Blurry or low-resolution images — may indicate a Photoshopped document.
  • No lab name or contact information — legitimate labs put their name and credentials on their reports.
  • Suspiciously perfect results — 99.99% purity with zero impurities on every single product is statistically unlikely.
  • Reused across multiple products — the same COA PDF appearing for different compounds or batch numbers.

What a Good COA Looks Like

A trustworthy COA will have:

  1. Clear identification of the compound tested
  2. Batch/lot number matching your product
  3. HPLC purity with chromatogram graph
  4. Mass spectrometry confirmation with observed vs. theoretical MW
  5. Name and contact info of the testing laboratory
  6. Date of analysis within the last 12 months
  7. Signature or authorization from the lab

The Bottom Line

A COA is only as good as the lab that produced it and the vendor's willingness to provide batch-specific results. Always request a COA before purchasing, verify the batch number matches, and look for third-party testing from a recognized independent laboratory.

This article is for educational purposes only. TruPeptide does not sell peptides or endorse any specific vendor.