How to read a peptide Certificate of Analysis

A Certificate of Analysis is the single most important document a peptide supplier publishes. Most consumer brands do not publish one. Some publish documents that are technically COAs but are missing the tests that actually matter. If you are buying research peptides, this is the document you should be reading first.

The four tests that matter#

For any injectable peptide, four tests cover the credibility floor. If any of them is missing, the COA is incomplete regardless of how official it looks.

Identity#

Done by mass spectrometry - usually LC-MS or MALDI-TOF. This confirms that the molecule in the vial has the expected molecular weight. Without identity testing, “BPC-157” on the label is just a claim. A reputable lab reports the observed m/z next to the theoretical value, and any deviation greater than a fraction of a Dalton is suspicious.

Purity#

Reverse-phase HPLC is the standard. The result is reported as a percentage based on the relative area of the main peak versus everything else. The credibility floor is ≥ 98%. Below 95%, you are buying meaningful quantities of truncated peptides, byproducts, or solvent residues. Some sellers advertise “HPLC tested” without publishing the actual percentage - that is meaningless.

Endotoxin#

This is the test most consumer peptide brands quietly skip. Bacterial endotoxins (lipopolysaccharides) trigger immune responses regardless of the peptide’s intended effects. The standard method is LAL (Limulus amebocyte lysate), and pharmacopeial limits are typically expressed in EU (endotoxin units) per milligram. A clean batch should report well below the limit, often less than 1 EU/mg.

Sterility#

USP <71> is the gold standard - a 14-day incubation in two growth media checking for any bacterial or fungal growth. “Visual inspection” is not sterility testing. If the COA does not specify the method, assume the product was never actually tested for sterility.

Lab credentials to look for#

• ISO/IEC 17025 - international standard for testing-lab competence. Specific to analytical chemistry methods.
• CLIA accreditation - US clinical-lab certification. Common in labs that also serve pharma research.
• cGMP-aligned facility - Current Good Manufacturing Practice. Required for anything heading toward clinical use, useful as a signal even for research-grade material.

A COA from a lab without any of these is not necessarily fake - but it has not been independently audited. Treat it accordingly.

Red flags#

• No lot number, or lot does not match the vial. If the COA cannot be traced to the specific batch in your hand, it is decorative.
• Missing endotoxin or sterility section. Almost always means the test was not performed.
• Purity reported without HPLC peak data. “Purity: 99%” with no chromatogram is a number on a page.
• Identical COA across every batch. Real batches produce real variation. Copy-paste documents from a single template should make you pause.
• No analyst signature or release date. An unsigned COA is a draft. Drafts are not COAs.

What we do#

Pepmod tests every production batch independently - identity, purity, endotoxin, sterility - and publishes the full COA on the transparency page. Lot numbers tie one-to-one to the vial in your hand. If a batch fails any of the four tests, that batch does not ship. We would rather hold inventory than ship something we cannot stand behind.