How to Read a Certificate of Analysis (COA)

A Certificate of Analysis (COA) is a lab document that reports what a specific batch of material actually contains. For peptides sold as “research chemicals,” it is the only objective window into quality you have — but a COA is only as trustworthy as the lab behind it and the batch it describes. This guide explains what the tests mean and how to tell a real COA from a meaningless one.

What a COA is (and is not)

A COA documents test results for one identified batch (lot) of one product. It should name the compound, the lot number, the manufacture or test date, the methods used, and the lab that ran them. It is not a safety clearance, a quality guarantee for every vial, or evidence that the product is legal or appropriate for human use. A COA tells you what was in the sample the lab tested — not necessarily what is in the vial you hold.

The core tests: purity and identity

Two tests do most of the work, and they answer different questions.

HPLC (high-performance liquid chromatography) measures purity. It separates the contents of a sample over time; each component shows as a peak. Purity is usually reported as the area of the main peak divided by the total area of all peaks (“area under the curve”), expressed as a percentage. A “98%” result means the target peptide accounts for 98% of what the detector saw — the other 2% is other peptide-related species. Important caveat: HPLC purity is relative to what the method detects. It does not weigh water, salts, or counter-ions, and it cannot by itself prove the main peak is the right molecule.

Mass spectrometry (MS) answers identity: it measures molecular weight so you can compare the observed mass against the theoretical mass for that sequence. A close match (typically within roughly half a dalton for these methods) supports that the compound is what the label claims. Purity without identity is hollow — a sample can be 99% pure and still be 99% of the wrong thing. A credible COA shows both.

The safety-oriented tests

For anything intended to be reconstituted and injected, contamination matters more than purity. These tests are governed by United States Pharmacopeia (USP) standards:

Sterility (USP <71>) — whether the material grew detectable bacteria or fungi.
Bacterial endotoxin (USP <85>) — endotoxins are lipopolysaccharides from the outer membrane of Gram-negative bacteria; they are heat-stable, survive ordinary sterilization, and cause fever and inflammation. Tested by the LAL (Limulus amebocyte lysate) method or, more recently, recombinant reagents such as recombinant Factor C (USP <86>, official May 2025), and reported in endotoxin units (e.g., EU/mg). For injectable drugs the threshold human pyrogenic dose is 5.0 EU/kg per hour (far lower, 0.2 EU/kg per hour, for the intrathecal route).
Heavy metals — lead, arsenic, mercury and similar, from synthesis or raw materials.

Most research-grade peptide COAs report purity and identity only and omit these entirely. That gap is itself information.

Third-party vs vendor-supplied

A third-party COA comes from an independent, ideally ISO/IEC 17025-accredited lab with no stake in the sale. (ISO/IEC 17025 is the international standard for the competence of testing and calibration laboratories.) A vendor-supplied (in-house) COA is generated by the seller. The latter is not worthless, but it carries an obvious conflict of interest and is trivial to fabricate. Prefer COAs naming an identifiable independent lab, on the lab’s letterhead, with contact details you can verify.

Spotting fake, stale, or meaningless COAs

Red flags:

No lot number, or a lot that doesn’t match the vial. A COA for a different batch tells you nothing about your product.
Stale or recycled. One COA reused across every batch for years; no date; a manufacture date long before your purchase.
No methods or no lab named. “Purity: 99%” with no chromatogram, no instrument, no analyst.
Missing the chromatogram/spectrum images. A number without the underlying trace can’t be checked.
Impossible perfection. “100.0%” purity, or identical numbers on every product.
Mismatched details — wrong molecular formula, sequence, or theoretical mass for the named compound.
Editable files with altered fonts, crooked text, or inconsistent formatting.

When a lab is named, you can sometimes contact it to confirm the report is real.

Bottom line

A strong COA is batch-specific, recent, from a named independent lab, and shows both HPLC purity (with the chromatogram) and MS identity (observed vs theoretical mass) — plus sterility and endotoxin data for anything injectable. Treat a number with no chromatogram, no lot, no date, or no lab as marketing, not evidence. And remember the larger context: as of 2026, peptides sold this way are not FDA-approved for human use, and a clean COA changes none of that. (Even where a peptide may be eligible for pharmacy compounding, that is not the same as FDA approval.) This is reference information, not medical advice.