What a Certificate of Analysis Can and Cannot Tell You

Many sellers of research peptides post a certificate of analysis, usually shortened to COA, next to each product. A COA can be useful evidence, but only for the specific questions its tests answer. This guide explains what a complete COA contains, how to check that it applies to the product in front of you, and what it cannot tell you.

What a COA is

A COA is a report of laboratory tests on a sample from one batch, or lot, of material. In regulated drug manufacturing, FDA's good manufacturing practice guidance for active pharmaceutical ingredients describes what an authentic certificate should include: the name of the material, its batch number and release date, each test performed with its acceptance limits and numerical results, a date and signature from authorized quality personnel, and the name, address and telephone number of the manufacturer or of the laboratory that did the analysis ^{Source [1]}.

Research-grade materials are not necessarily made or tested under those rules. The list is still a useful benchmark for what a complete report looks like, and for noticing what is missing.

The tests a COA may report

Each test answers a different question, and a COA answers only the questions it lists.

• Identity, usually by mass spectrometry: does the measured mass, and ideally a fragment pattern, match the expected molecule? Researchers analyzing peptide vials bought online confirmed identity this way, alongside separate tests for content and purity ^{Source [2]}. An identity result should name the exact molecule, including any salt form or modification.
• Purity, usually by high-performance liquid chromatography (HPLC): what share of the detected signal belongs to the main peak? Peptide synthesis can leave shortened chains and side products that look structurally much like the target, and detecting and measuring them takes advanced analytical methods ^{Source [3]}.
• Quantity or content: how much of the peptide is actually present, by weight or per container. This is a separate measurement from purity.
• Microbial quality and bacterial endotoxin: FDA treats sterility, endotoxin and particulate testing as critical safety attributes for injectable products ^{Source [4]}. If these tests are absent, the COA tells you nothing about them.

A test that is not listed was not reported. In its 2026 reviews, FDA found that publicly available COAs for BPC-157 generally reported only a purity result, with no impurity limits or results ^{Source [3]}, and that the TB-500 COAs it examined lacked tests for impurities, aggregates, microbiological quality and bacterial endotoxin ^{Source [4]}.

Check that the COA applies

A COA is only relevant to the batch it describes. Before reading the results, check the link between the document and the product.

• Batch or lot number. Does it match the number on the container or the order? A COA with no batch number cannot be tied to any product.
• Dates. When was the sample tested, and is there a retest or expiry date?
• Exact substance and form. Does the named substance match exactly, including the salt form? In nominations FDA reviewed in 2026, attached COAs described an acetate salt that did not match the substance as nominated ^{Source [3]}. For TB-500, a registry number and molecular formula supplied with the nomination matched neither the free base nor the acetate ^{Source [4]}.
• Limits next to results. A result without an acceptance limit cannot show whether the batch met a stated specification.

Who issued it

A report prepared by a seller's own staff is different from one issued by an independent laboratory. Under FDA's GMP guidance, a certificate should be dated and signed by authorized quality personnel and should give the name, address and telephone number of the manufacturer or, for a certificate reissued by a distributor, of the laboratory that performed the analysis ^{Source [1]}. To confirm a report, contact the laboratory through details you find yourself, not through a link or number printed on the document, and ask whether it issued that report for that sample. Our guide on checking a supplier's official domain covers related checks.

What accreditation means

Accreditation is an independent evaluation of a laboratory's impartiality and competence against recognized standards; for testing laboratories, that standard is ISO/IEC 17025 ^{Source [5]}. In the United States, NIST's NVLAP program, for example, assesses laboratories against ISO/IEC 17025:2017 and publishes a directory of accredited laboratories ^{Source [6]}.

Accreditation is not blanket approval. It is issued with a scope of accreditation that lists the specific test methods covered, and NVLAP-accredited laboratories may use the accreditation mark only on reports describing work within that scope ^{Source [7]}. A laboratory can be accredited for some tests and not for the ones on your COA, so check the scope and the expiry date, not just the logo.

What a purity percentage does not tell you

A high purity number is the most quoted line on most COAs, and the easiest to misread.

• It is not the amount. Synthetic peptides are usually obtained as salts. In a 2025 analysis, the trifluoroacetate counterion made up as much as 35% of the weight of peptide salts, and the authors stress that counterion content must be accounted for ^{Source [8]}. A purity figure does not report that weight.
• It is not identity. A clean peak shows that one component dominates, not that it is the intended molecule.
• It is not sterility or endotoxin. When researchers bought semaglutide vials from illegal online pharmacies, no viable microorganisms were found, yet every sample contained endotoxin, and measured purity was far below the 99% printed on the labels ^{Source [9]}.
• It is not evidence of effect or safety for any use.

For a closer look at the three core measurements, see purity, identity, and quantity are different measurements.

The bottom line

Research materials and consumer products belong to different categories. A listing, laboratory report, or research-use label does not establish suitability for personal use. A COA is evidence for the tests it lists, on the batch it names, from the laboratory that issued it, and nothing beyond that.