How to Read a Peptide Certificate of Analysis (COA)

Research peptides are not regulated like pharmaceutical drugs. There is no FDA oversight of purity, potency, or sterility for compounds sold as research chemicals. The Certificate of Analysis (COA) is your only verification that what is in the vial matches what is on the label. A legitimate supplier will provide a COA for every batch, either included with the product or available on their website. If a supplier cannot provide a COA, do not buy from them.

High-Performance Liquid Chromatography (HPLC) is the standard method for measuring peptide purity. The result is expressed as a percentage — for example, 98.5% purity means that 98.5% of the material in the vial is the target peptide, and 1.5% is impurities (synthesis byproducts, truncated sequences, or degradation products).

What to look for: 98% or higher is considered good quality for research peptides. 95-98% is acceptable but lower quality. Below 95% suggests a poor synthesis or degraded product.

The HPLC chromatogram (graph) should show one dominant peak. Multiple peaks of similar size indicate significant impurities. Some COAs include the chromatogram image; others only report the percentage.

Mass spectrometry confirms the molecular identity of the peptide — it verifies that the compound is actually what it claims to be, not just that it is pure. The result is reported as a molecular weight in Daltons.

The observed molecular weight should match the expected molecular weight of the peptide within a narrow tolerance (typically ±1 Dalton). For example, BPC-157 has an expected molecular weight of 1419.53 Da. If the COA shows a mass of 1419.5 Da, that confirms identity. If it shows 1350 Da, the vial does not contain BPC-157.

This is arguably the most important test on the COA. HPLC tells you the material is pure, but mass spec tells you it is the correct molecule.

Endotoxins are bacterial cell wall fragments that cause fever, inflammation, and potentially dangerous immune reactions when injected. The Limulus Amebocyte Lysate (LAL) test measures endotoxin levels.

Results are reported in Endotoxin Units per milligram (EU/mg). For injectable peptides, the acceptable limit is less than 5 EU/mg (and ideally less than 1 EU/mg). Higher levels indicate contamination during manufacturing.

Not all suppliers test for endotoxins. For peptides you intend to inject, an LAL test result is important. For topical or oral peptides, it is less critical but still a quality indicator.

Sterility testing confirms that the peptide vial is free from microbial contamination (bacteria, yeast, mold). This is separate from endotoxin testing — a product can be sterile (no live organisms) but still contain endotoxins from dead bacteria.

Results should read "No growth detected" or "Pass." Sterility is essential for any peptide that will be injected. Lyophilized (powder) peptides are generally sterile from the manufacturing process, but reconstituted peptides can become contaminated if prepared improperly.

Some premium suppliers also test for specific pathogens and report residual solvent levels from the synthesis process.

No batch number: Every COA should reference a specific manufacturing batch. A generic COA that does not tie to a batch may be fabricated or reused.

Third-party vs in-house testing: COAs from an independent third-party lab (like Janssen, Intertek, or SGS) carry more weight than in-house testing by the supplier themselves. In-house testing is not inherently dishonest, but independent verification removes the conflict of interest.

Missing mass spec: If only HPLC is provided without mass spectrometry, you know the material is pure but not that it is the correct peptide. Unscrupulous suppliers could sell a cheaper peptide at a higher price.

Old dates: A COA from years ago may not represent the current batch. Peptide quality can degrade during storage, especially if not stored properly. Ask for a recent COA that corresponds to the batch you are purchasing.

Identical COAs across products: If every peptide from a supplier has suspiciously similar HPLC percentages (all exactly 99.0%, for example), the COAs may be fabricated.