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How to read a certificate of analysis · Updated October 13, 2026
A peptide COA is the certificate of analysis a laboratory issues for one production lot of a research compound. It names the lot and the testing lab, then reports results such as identity, HPLC purity and fill. To read one, match its lot number to your label and check each result against its stated method.
For research materials and lot documents, explore Curo’s full research catalog or view kits for Retatrutide, GHK-Cu and KLOW.
For further reading, visit Curo Insights.
A COA describes one lot. A purity figure on a product banner with no matching report is an unverified claim.
Reading a peptide COA starts with the lot number, lab name, test date and method, before any result.
Purity shows how much of a sample is one substance. Identity shows which substance it is. A useful report carries both.
A missing lot number prevents a direct match to the material; an unnamed lab makes independent confirmation harder.
COA stands for certificate of analysis. In peptide work it is the document a testing laboratory writes after running analytical methods on a sample from one production lot. A COA covers that lot only. On its own it says nothing about a brand, a catalogue or the next production run.
Two containers can carry the same compound name and still come from different synthesis runs, so their results can differ. A report with no link to the lot number on your label says little about the material you hold. An annotated certificate walkthrough sets a complete report beside two incomplete ones.
Go through each certificate in a fixed order so nothing gets skipped. A typical report has these fields.
Lot number. Compare it character by character with the lot printed on the label.
Laboratory name and report ID. The lab should be named, and it should be able to look up the report ID.
Test date. An undated result cannot be placed against the material you hold.
Identity. This is a spectral match by FTIR or a measured molecular mass by LC-MS, depending on the lab.
Purity. HPLC gives the target's share of all detected peak area, as a percentage.
Fill. This is the measured amount of material, in milligrams per container.
Endotoxin and sterility. Some reports include these and some do not, so check whether the lab ran them.
Each result should name its method, since a bare number cannot be compared with anything. Fill and net content are different figures. Net peptide content counts only the peptide and leaves out water and counterions, as peptide quality-control recommendations explain.
Match a peptide COA by searching the exact lot number on the label. The searchable lot COA library is one place to run that check; its lot-verification instructions explain the fields to compare.
Find the lot number on the label of your research compound.
Search that exact number in the supplier's lot lookup or on the product page.
Confirm that the compound name and the fill match what the label says.
Follow any verification link back to the issuing lab and confirm the numbers there.
HPLC, or high-performance liquid chromatography, separates a sample into its components as they pass a detector. HPLC purity is the area of the target compound's peak as a percentage of every peak the detector recorded in that run. A result of 99 percent means the target made up about 99 percent of the detected signal.
The figure does not name the molecule behind the main peak. The same quality-control recommendations note that one large peak in a UV trace may or may not be the intended product, and that mass spectrometry shows which peak is which. Peptide purity testing therefore pairs HPLC with an identity method. The percentage also says nothing about water content or counterion load.
Endotoxin is a separate question. HPLC does not measure endotoxin, so a high purity result says nothing about it. The bacterial endotoxins test is its own assay, and the FDA guidance on endotoxin testing describes the gel clot, photometric and kinetic methods behind it, as of its March 2026 edition.
Third-party means the laboratory is independent of both the supplier and the manufacturer. The supplier is not grading its own work, and the report carries a lab name you can contact. A peptide COA written by the seller offers no such check.
The linked lot testing summary describes identity by FTIR or LC-MS, depending on the laboratory, HPLC purity and fill in milligrams. Endotoxin and sterility are listed only where the laboratory ran those assays, as of October 2026. The quality and testing standard explains what each test measures. Confirm which results appear on the report for the exact lot you are checking.
Missing fields on a peptide COA limit what a researcher can verify. Look for these gaps before relying on a result.
No lot number, or a lot number that differs from the one on your label.
No named laboratory and no report ID.
No test date.
A purity percentage with no method and no chromatogram.
Purity with no identity result anywhere on the page.
Ask the supplier or issuing lab to resolve each missing field. A lab may confirm a document that lacks a public lookup, but a purity result still cannot establish identity, and a report without a matching lot cannot establish the result for your material. The supplier qualification checklist covers the operating records a COA does not address.
Purity shows how much of a sample is a single substance, usually as HPLC peak area. Identity shows which substance it is, by FTIR spectral match or LC-MS molecular mass. A sample can score high on purity and still be the wrong molecule, so a report should carry both results.
No. A COA is a document format, and anyone can write one. Third-party testing means an independent laboratory ran the analysis and put its name on the report. Check who issued the document, whether it carries a report ID, and whether the lab will confirm it when asked.
No. Endotoxin and sterility are separate assays, and some reports leave them out. When a report has no endotoxin line, treat endotoxin as untested, not as passed.
No. A certificate belongs to the lot it names. If a seller shows one document for several lots, or the lot on the document differs from the lot on your label, the report cannot be matched. Ask for the report that carries your lot number and confirm it with the issuing lab.
Browse the current research catalogue and check the lot documents in the COA library. Catalogue materials are supplied for research use only, not human or veterinary use.