How to Read a Peptide COA: A Line-by-Line Guide With Annotated Examples

How to read a peptide COA

Read every certificate in the same order. Each pass either resolves or fails.

1. Lot number. Find the lot on the certificate and the lot on the vial, then compare the characters. If the certificate carries no lot, or a lot that differs from the vial, stop. Curo's help center covers how to verify a certificate against your lot step by step.
2. Issuing laboratory and report ID. A certificate should name the laboratory that produced it and carry a report identifier that laboratory can look up. An unbranded PDF with no issuer is unverifiable by design.
3. Date of analysis. Testing has a time component. An undated result leaves you guessing whether it describes the material now in the vial or a run from two years ago.
4. Method. The document should name the analytical method for each result. HPLC for purity, mass spectrometry or FTIR for identity, LAL or gel clot for endotoxin. A result without a stated method cannot be compared to anything.
5. Purity with the chromatogram. A bare percentage is the weakest form of a purity result. The chromatogram shows the main peak, the baseline, and the impurity peaks the percentage summarizes. Read the trace, not the headline.
6. Identity confirmation. Compare the identity result against the compound the vial claims to hold, whether that's an observed mass from LC-MS or a spectral match from FTIR. This is the pass that catches a clean sample of the wrong molecule.
7. Endotoxin. A peptide can reach high chromatographic purity and still carry bacterial endotoxin from synthesis and handling. Endotoxin is a separate assay with a separate result line.

A certificate that clears all seven passes is inspectable. One that clears three is a picture of a document, not proof of one.

Annotated examples

The three examples show a real certificate, a common gap, and a certificate stripped of its two anchors: the lot and the lab. Field names are the certificate's own labels.

a. A complete certificate

Curo publishes every lot's certificates at /coa. The BPC-157 5mg lot BPC05SR526, tested by BTLabs on 5/28/2026, carries three linked documents: an HPLC purity and potency assay, an FTIR identity and composition analysis, and a separate bacterial endotoxin test.

Verdict: this certificate names the lot, the lab, the method, and three separate assays with their specifications. It clears all seven passes from the section above.

b. A certificate with a purity number and no identity panel

This is a typical example built to show the gap, not a real vendor's document. A one-page sheet lists a compound name, a lot number, and a single HPLC purity result. No identity method appears anywhere on the page.

Verdict: a high purity number with no identity test can describe a clean sample of the wrong molecule. This is the exact failure mode the identity pass exists to catch, and this certificate has nowhere to catch it.

c. A certificate with no lot number and no issuing lab

Also a typical example, not a real document. A results table appears with numbers that look complete at a glance: purity, a mass figure, an endotoxin pass. No lot number ties it to a specific batch, and no laboratory name or report ID appears anywhere on the page.

Verdict: numbers without a lot and a named lab are not a certificate. They are a claim formatted to resemble one. Both anchors, the lot and the lab, have to be present before any result on the page is checkable.

What does 99% purity mean for peptides?

A 99 percent purity figure on a peptide COA means that in a single chromatographic run, the main peak accounted for about 99 percent of the total peak area detected. It is a measure of how much of what the detector saw was one substance. It is a real number with a narrow meaning.

What that number does not carry on its own: it does not confirm which molecule the main peak is, since a pure sample of the wrong sequence still reports high purity; it does not account for anything the detector does not see at the chosen wavelength; it does not report water content, residual solvent, counterion load, or fill weight; it does not include endotoxin; and it does not transfer to any lot other than the one tested.

So a "99% purity" banner with no lot-matched certificate behind it is a marketing claim rather than a measurement. The claim becomes a measurement at the moment you can open the certificate for your lot and read the method that produced the figure.

What a peptide COA cannot tell you

A COA is a snapshot of one lot at one moment, taken with one set of methods. It cannot tell you how the material was stored after testing, how it moved from manufacturer to lab to warehouse to bench, or whether the next lot was handled the same way. It cannot tell you whether the rest of the catalog is tested at the same standard, and it cannot prove the supplier will still exist next quarter.

Storage after receipt is the failure mode buyers underrate. A well-documented lyophilized peptide degrades under poor handling like any other. The storage and stability guide covers that side.

The six-point purity checklist

Before treating any purity claim as meaningful, confirm six things.

1. Batch connection

The certificate connects to the lot being sold, not a sample lot from an earlier run. A floating example document is weaker than a lot-linked one, and a product-page badge is weaker still.

2. Named laboratory

The document names the laboratory that issued it. Court records in the July 2026 federal case against the owner of Paradigm Peptides showed the defendants admitted producing fake certificates, the failure this check exists to catch.

3. Stated method

HPLC, identity testing, and endotoxin results each carry the method that produced them. Named methods are comparable across suppliers; unnamed results are not.

4. Identity, separate from purity

Purity asks how much of the sample is one thing. Identity asks whether that thing is the compound on the label. Both belong on the certificate.

5. Public verification

The certificate is readable before purchase, without an account, so the claim can be checked while it still matters. Curo's COA database is open for that reason.

6. Consistency across the catalog

One strong product page does not prove a catalog. Look for the same testing panel on every lot of every product, per Curo's quality and testing standard.

Why vendor archives and independent testing disagree

A published archive of certificates and an independent blind purchase are different classes of evidence, and they do not always agree. An archive shows what a supplier chose to publish. A blind purchase tests what a supplier actually ships an ordinary buyer.

Independent blind-purchase programs have published results that disagree sharply with the same vendors' own archives, including purity figures far below the certificate values. Curo's own independent records are listed alongside its certificates for that comparison.

When the two disagree, weight the blind purchase more heavily, and weight both above any purity number printed on a banner.

Why "US-made" and "cGMP" need the same scrutiny

Purity is one of several phrases asked to carry more than it can. "cGMP" describes a manufacturing standard, and it means something only when a supplier says which facility holds it and for which step. A country-of-origin claim means something only when it says which step happened where: synthesis, finishing, testing, or fulfillment.

Curo's own language is deliberately narrow here. Orders are fulfilled from the United States, a statement that covers fulfillment and stock location, not where synthesis happened, because merging those would be the same shortcut this page warns about. Material covered by this guide is sold under Curo's research use only policy and is not evaluated here for any other use.

COA questions that change by compound

The seven passes apply everywhere. Some compounds add a question the generic checklist misses.

• Known-mass peptides. For BPC-157, the observed mass should match 1419.6 g/mol, as covered in the BPC-157 research record.
• Fragments under a parent protein's name. A certificate can be accurate and still leave you reading the wrong literature, the case in how TB-500 relates to thymosin beta-4.
• Blends. One purity figure cannot describe four peptides at once, the problem worked through in KLOW: four peptides, one certificate.
• Metal complexes. Purity does not establish that a metal is coordinated to the peptide, covered in the GHK-Cu profile.
• Catalog names covering several molecules. NAD+ covers an oxidized form, a reduced form, and two precursors under one name, per what NAD+ trials measure and administer.

For a repeatable way to score several suppliers side by side on documentation, see how to evaluate research peptide companies. The current vendor field, including closures and federal actions, is covered in best peptide companies in 2026.

About this guide

This guide is maintained by Curo's documentation team. The reading method and the field-by-field breakdown come from certificates published at the COA lookup page alongside the public lab report formats used by Janoshik and BTLabs, two laboratories active in the research peptide market. It was last reviewed on 2026-09-09. The wider numbers on testing, regulation, and the market are collected in peptide industry statistics 2026.

The tables in this guide are available under CC BY 4.0. You may reproduce them with attribution; see the data license for terms.

FAQ

What is a peptide COA?

A certificate of analysis for a peptide is the laboratory report for one production lot: compound, lot number, test date, methods run, and results, typically purity by HPLC, an identity confirmation, and an endotoxin figure. It documents that lot alone.

How do I read a peptide COA?

Check seven items in order: the lot number against the vial, the issuing laboratory and report ID, the date of analysis, the method behind each result, the purity figure with its chromatogram, the identity confirmation, and the endotoxin result. Any missing item is a gap.

Is a 99% purity claim enough?

No. It describes main-peak area in one chromatographic run on one lot. Without a lot-matched certificate naming the laboratory and method, it is a marketing claim, and it says nothing about identity or endotoxin.

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

Purity measures how much of the tested sample is a single substance, usually by HPLC peak area. Identity confirms which substance that is, by mass spectrometry or FTIR spectral matching. A sample can be highly pure and still be the wrong molecule.

Should a peptide COA include endotoxin testing?

Yes. Chromatographic purity does not detect bacterial endotoxin, introduced during synthesis, handling, or filling. Endotoxin is a separate assay with its own result line. Curo runs it alongside HPLC and identity testing on every lot.

Where can I see a supplier's peptide COAs before buying?

A supplier relying on documentation should publish certificates before purchase and without an account. Curo's certificate library is public and lot-matched, and the verification guide shows how to match a certificate to your vial.

Does a COA prove a supplier is trustworthy?

No. It documents one lot. Company identity, catalog-wide consistency, storage handling, and payment recourse sit outside the certificate. Blind-purchase testing has disagreed with vendor-published archives, so weigh the certificate as one input among several.