How to read a peptide certificate of analysis
A breakdown of every field on a typical research-peptide COA — what HPLC purity actually measures, how endotoxin limits are interpreted, and which red flags should send you back to the vendor.
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A peptide Certificate of Analysis (COA) is the analytical record that a research-grade vendor ships alongside every lot. It documents what was actually in the vial, who tested it, and to what spec. Most peptide vendors do not publish COAs publicly. Lumin Research does, because the document is the product as much as the powder is.
This guide breaks down the fields on a typical COA so the reader knows what to look for, what each measurement actually constrains, and which omissions are quietly disqualifying.
Identity verification
The top block of a COA names the compound, its target molecular formula, and its theoretical mass. A credible report pairs that target with a measured value from mass spectrometry — typically MALDI-TOF or ESI-MS. The measured mass should fall within a single dalton of the theoretical for a peptide under five kilodaltons. Anything broader suggests the analytical method was not run, or was run badly.
Purity by HPLC
HPLC purity, usually expressed as a percentage at a fixed wavelength (commonly 220 nm), is the headline figure. A 99.0% purity at 220 nm means the target peptide accounts for 99.0% of the chromatogram area at that detector setting. It does not measure microbial contamination, residual solvents, or counterion content — only the relative abundance of UV-absorbing species. Any vendor reporting "99% purity" with no chromatogram attached is reporting a number, not a measurement.
Endotoxin and microbial limits
For research peptides reconstituted into solution, residual bacterial endotoxin is the contamination class that matters most. The standard test is LAL (Limulus Amebocyte Lysate). Lot-release specifications vary by application, but the figure should be present, the method named, and the limit stated. A COA that omits endotoxin entirely is not a research-grade COA.
Red flags
Watermarked PDFs without a testing-laboratory name. Identical chromatograms across multiple lots. Purity figures with no wavelength specified. Mass spectra that show only the target peak with no baseline — a hallmark of a fabricated trace. When in doubt, the analytical desk publishes the underlying file.
References
Authoritative literature on peptide analysis and endotoxin testing:
- HPLC methods for peptide purity — PubMed / NIH research
- LAL endotoxin testing standards — U.S. Pharmacopeia and FDA guidance
All citations link to the U.S. National Library of Medicine's PubMed database or official pharmacopeial standards. Lumin Research publishes a third-party Certificate of Analysis for every lot, including HPLC chromatograms and endotoxin results, as part of our verification-first approach to research-grade peptides.