COA basics

What is a peptide COA test?

By The Merit Research Team

A peptide COA (Certificate of Analysis) is a document from an independent laboratory certifying the identity and purity of a specific peptide lot. It includes the compound name, lot number, test date, testing method, and a measured purity result. COAs are the primary way to verify that research peptides match their label claims.

What a COA contains

A well-formed COA includes: the name of the compound tested (e.g. BPC-157, Semaglutide), the specific lot or batch number, the test date, the laboratory name and contact information, the testing method (usually HPLC or HPLC-MS), and the measured purity result — typically expressed as a percentage. Some labs also report retention time, molecular weight, and chromatogram traces. The absence of any of these fields is a yellow flag.

What "independent" means

A COA is only as useful as the independence of the lab that issued it. A lab controlled by the vendor — owned by the same company, staffed by the vendor's employees, or inaccessible to third-party audits — cannot produce a meaningfully independent result. An independent lab accepts samples from any party, publishes results it cannot alter after the fact, and has verifiable contact information separate from the vendor. Most legitimate peptide testing is done at Janoshik Analytical, Benchmark Analytical (now Analytical Resource Center), or Research Resource Center.

HPLC vs. HPLC-MS — what the method tells you

HPLC (High-Performance Liquid Chromatography) separates a sample's components and measures their concentrations. It's the standard for peptide purity testing. HPLC-MS adds a mass spectrometer to confirm the molecular identity of each peak — it's more definitive for confirming you have the right compound, not just the right purity. A COA that reports only HPLC purity is decent evidence; one that includes mass spec confirmation is stronger. Some COAs also list the instrument model and serial number, which makes forgery harder.

What COAs can and cannot tell you

A COA certifies the specific lot it tested — not every vial in the vendor's current inventory, and not the vial you specifically receive unless you've matched lot numbers. Purity is not safety: a 99% purity result measures peptide identity and concentration; it doesn't screen for residual solvents, heavy metals, endotoxins, or microbial contamination. Some vendors commission those additional panels; most don't.

How Merit Verified uses COA data

Merit Verified indexes COAs from public sources and independent aggregators. Each COA is linked to the specific vendor, peptide, lab, and lot where the data is available. The Merit Score for each vendor is calculated from the volume of independent COAs on file, the reputation of the labs behind them, the measured purity results, and how recently they were tested. A vendor with no independent COA on file is shown as Unscored — never assigned a flattering middle number.

Browse indexed COAs Independent labs registry How to read a COA

Frequently asked questions

What is a COA for peptides?

A COA (Certificate of Analysis) is a document from an independent third-party laboratory that certifies the identity and purity of a specific peptide lot. It includes the compound name, lot number, test date, testing method (usually HPLC or HPLC-MS), and measured purity percentage. COAs are the primary independent verification tool in the research peptide market.

What does HPLC mean on a peptide COA?

HPLC stands for High-Performance Liquid Chromatography — the standard testing method for peptide purity. The test separates a sample's components and measures each component's concentration. The result is typically expressed as a purity percentage. HPLC-MS adds a mass spectrometer to confirm molecular identity, making it more definitive than HPLC alone.

Is a COA the same as a purity test?

A COA includes purity data but is more than a purity number. A well-formed COA also confirms compound identity, lot number, test date, lab identity, and method. A purity number without the surrounding documentation — lab letterhead, lot number, method — is much weaker evidence. Always ask for the full COA, not just the stated purity.

How often should a peptide vendor get new COAs?

There is no universal standard, but COAs age. Merit Verified applies age decay in its Merit Score — a test from 18+ months ago is worth significantly less than a recent one, because a vendor's manufacturing practices, suppliers, or stock can change. A vendor whose most recent COA is from two years ago and who continues to sell new inventory has a meaningful evidence gap.

What is the difference between identity testing and purity testing on a COA?

Identity testing confirms you have the right compound — that the molecule matches the expected molecular weight and structure (typically done via mass spectrometry). Purity testing measures what fraction of the sample is the target compound versus everything else (done via HPLC). A COA that only reports purity can't confirm you have the right peptide; a COA with both identity and purity testing is more complete evidence.

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