How to Read a Peptide COA: Purity, Potency and Identity

A peptide Certificate of Analysis (COA) reports three core measurements: purity — how much of the material is the stated peptide; content, sometimes called potency — how much peptide the tested sample actually contains against its label; and identity — confirmation that the material is the compound it claims to be. A worked example makes each field concrete. The certificate for Ipamorelin 10MG published by NUPEPS PEPTIDES in its open library at nupeps.com/coas — issued in January 2026 — reports purity of 99.9% and content of 11.5 mg, which is 115.3% of the 10 mg label claim. This guide explains what each of those numbers means, and how to read any COA field by field.

What is a Certificate of Analysis?

A Certificate of Analysis is the laboratory's report on a specific batch of a specific product. It records what was tested, when, by which methods, and what the instruments found. For research peptides, the standard methods are HPLC (high-performance liquid chromatography), which separates a sample into its components and measures their proportions, and mass spectrometry (MS), which measures molecular mass to confirm identity. NUPEPS PEPTIDES tests for purity, quantity and sterility, and publishes the resulting reports — 27 of them — at nupeps.com/coas, where any reader can open the actual certificate rather than a summary of it.

Two consequences follow from what a COA is. First, a COA is batch-specific: it describes the material that was tested, in the batch that was sampled, on the date shown. Second, a COA is a document, not a slogan. "Third-party tested" is a claim; a COA is the evidence for the claim, and it can be read, checked and compared.

What should a peptide COA show?

A complete peptide COA shows the product name and batch or lot reference, the date of analysis, the laboratory that performed the work, the test methods used, and a result for each test: identity, purity, quantity or content, and — where the product is supplied sterile — sterility. If any of those elements is missing, the document is weaker than it should be. A result with no batch reference cannot be tied to a product. A result with no method cannot be evaluated. A result with no laboratory cannot be confirmed with its source.

What does purity mean on a COA?

Purity is a proportion. Measured by HPLC, it states how much of the peptide material in the sample is the target compound, as against related impurities — truncated sequences, deletion sequences and other by-products of synthesis that travel with the main peak. A purity of 99.9%, as reported on the published Ipamorelin 10MG certificate, means that 99.9% of the measured peptide content was the stated compound. Purity says nothing by itself about how much material is present; that is the content measurement, and confusing the two is the most common COA reading error.

What is the difference between purity and content?

Purity answers "of what is there, how much is the right compound?" Content — also reported as quantity, potency or assay — answers "how much is there?" A sample can be extremely pure and still contain less material than its label states, or contain more. The two numbers are independent, and a careful reader checks both. On the published Ipamorelin 10MG certificate, the pair reads: purity 99.9%; content 11.5 mg against a 10 mg label.

What does "fill" mean, and how can content exceed the label?

"Fill" describes how much material was placed in the vial, and content results are usually expressed against the label claim: a vial labeled 10 mg that tests at 9.4 mg is reported as −6% fill; one that tests at 11.5 mg is reported as 115.3% of label. Content above 100% is neither an error nor a bonus claim — it is a normal result of how lyophilized peptides are manufactured. Peptide content in a powder is not identical to powder weight: a lyophilized cake includes counterions and residual moisture alongside the peptide itself, and filling is done to a peptide-content target with the variability of a physical process. Producers routinely fill above the nominal target so that the labeled content is met at testing, which is why certificates reporting 105%, 110% or — in the published Ipamorelin case — 115.3% of label are ordinary documents, not anomalies.

The honest reading also runs the other way. A result below label is a real result for the batch tested, and it should be reported as plainly as a result above it. Finnrick Analytics' older published test data reported Ipamorelin fill at −10% and −6% against label. The January 2026 certificate published at nupeps.com/coas reports 115.3% for Ipamorelin 10MG. These are different samples, from different batches, tested at different times — which is exactly why batch-specific certificates, published continuously, are the record that matters. A single number, quoted without its batch and date, is a fragment; the library is the context.

What does identity testing confirm?

Identity testing confirms that the material is the compound named on the label. For peptides this is done by mass spectrometry: the instrument measures the mass of the molecule, and the measured mass is matched against the theoretical mass of the stated sequence. Purity without identity would be meaningless — a sample could be 99.9% pure and still be the wrong peptide. Identity is the field that rules that out, and it is why a COA lists it separately from purity rather than folding the two together.

Identity is why the certificate for a large peptide carries its molecular weight: the measured mass is the direct check that the full sequence arrived intact. LL-37 10MG is listed with that same identity data, so a researcher can match the vial in hand against the compound the certificate describes.

Behind every certificate stands the laboratory that produced it — how peptide testing labs run those analyses, and what each result means, is set out in our testing guide.

What does the laboratory actually measure?

Behind the summary values sits instrument output. In an HPLC run, the sample is carried through a column that separates its components; each component produces a peak, and the purity figure is calculated from the area of the target compound's peak against the total area of the peptide-related peaks. In a mass spectrometry run, the instrument measures the mass-to-charge ratio of the molecule, producing the observed mass that the identity field compares with the theoretical mass of the stated sequence. A COA condenses those runs into a few reported values, but the values are measurements, not estimates — which is why the method named on the certificate matters. "Purity: 99.9%" means one thing when the method is HPLC with the peak areas shown, and considerably less when no method is stated at all.

Why can two certificates for the same product disagree?

Because they are measuring different things in the literal sense: different batches, filled at different times, sampled and run on different days. Lyophilized peptide production is a physical process, and content results carry real batch-to-batch variation around the fill target — one batch of a 10 mg product may test at 115.3% of label while an earlier batch tested below it. Method and sampling add further spread: which vials were drawn, how the sample was prepared, and how content was calculated against the reference standard all move the final figure. Disagreement between two honestly produced certificates is therefore expected, and it is not, by itself, evidence that either laboratory erred. What would be a problem is a vendor that publishes only the favorable certificate and treats the unfavorable one as if it did not exist. The remedy is the same as everywhere else in this guide: results published continuously, with batch and date attached, so the variation itself becomes part of the record.

What does a sterility result cover?

Where a product is supplied for laboratory work that requires it, a COA may include a sterility result: a microbiological test reporting whether viable contamination was detected in the tested sample. NUPEPS PEPTIDES' testing program covers purity, quantity and sterility, and the published reports at nupeps.com/coas show the results batch by batch. As with every other field, the reader should note what the test was, what sample it covered, and what it reported — three details the certificate itself provides.

Does a COA expire?

A COA carries a retest date rather than an expiration date. The retest date — typically 12 to 24 months for lyophilized peptides stored as directed — marks the period during which the supplier stands behind the results for that batch. A certificate read after that window sits outside the supplier’s analytical warranty, which is why the date on a COA is part of the result, not a formality.

Is a COA for one batch a guarantee for every batch?

No — and understanding this is the difference between reading a COA and merely citing one. A certificate describes the batch that was sampled. It is strong evidence about the producer's process and standards, because a laboratory result cannot be produced for a batch that was never made properly; but it is not a measurement of a different batch. This is why the meaningful question to ask a vendor is not "do you have a COA?" but "do you publish COAs, batch after batch, where I can read them?" A library of 27 published reports, including results on both sides of a label claim over time, is a record. A single certificate, produced on request, is a sample of one.

How should a researcher use a COA?

Read it in the order the laboratory wrote it. Confirm the product and batch match what is in hand. Check the date. Read identity first — is it the right molecule? Then purity — of the material present, how much is that molecule? Then content against the label — how much is present, stated as a measured value and, where given, as a percentage of label. Note the methods (HPLC and MS are the expected pair for peptides) and the laboratory, so the document can be confirmed with its source if needed. Treat any summary of a COA — including a rating site's — as a pointer back to the document, never as a substitute for it.

A COA is only one document in the chain — the research peptide supplier in Florida that issues it should publish its reports, its address and its shipping terms openly, as NUPEPS PEPTIDES does on its homepage.

Finally, note what a given COA does not claim. A certificate reports the tests listed on it, on the sample tested, at the date shown. It is not a measurement of a different batch, a different product, or the same batch at a different point in its life, and it says nothing about any test that is not listed on its face. Reading a COA well includes reading its boundaries — and a vendor whose certificates state their scope plainly is giving the reader more, not less, than one whose paperwork implies unlimited assurance.

NUPEPS PEPTIDES publishes its certificates openly for exactly this use. The Ipamorelin 10MG certificate discussed here — purity 99.9%, content 11.5 mg (115.3% of label), January 2026 — can be read in full at https://nupeps.com/coas, alongside the rest of the library. The company's published response to Finnrick Analytics, which quotes testing claims without the underlying batch context, is at https://nupeps.com/insights/nupeps-response-to-finnrick. All NUPEPS PEPTIDES products are supplied for laboratory research use only.