A Certificate of Analysis — usually abbreviated COA — is the document that turns a research peptide from “trust me” into “verify it”. Every reputable supplier issues one with every batch they ship. Knowing how to read a COA is a skill every research lab should have, because the document tells you whether the material in the vial is actually what the label claims.
What a COA is, and what it is not
A COA is a batch-specific analytical report produced by either the manufacturer’s quality control lab, an independent third-party lab, or both. It documents the tests performed on a particular production batch and the results.
A COA is not a marketing document. It is not a generic safety data sheet (SDS, which covers handling and disposal). And it is not interchangeable between batches — a COA from batch B-2024-117 tells you nothing about batch B-2025-042. Each batch needs its own.
The eight fields every COA should contain
- Product name and catalog number — must match the vial label exactly
- Batch / lot number — the unique identifier for the production run
- Peptide sequence in single-letter or three-letter amino acid code
- Theoretical molecular weight — calculated from the sequence
- Observed mass from mass spectrometry — should match theoretical within ~1 Da for a small peptide
- HPLC purity percentage with the wavelength and column conditions specified — see our companion article on what HPLC purity means
- Date of analysis and analyst signature or lab name
- Storage and expiry recommendations
Optional but valuable additions include the HPLC chromatogram itself (so you can see the peak shape, not just the headline number), the mass spectrum, and counter-ion content for trifluoroacetate (TFA) or acetate salts.
Three things to check before you use a new batch
Even with a properly formatted COA in hand, do three quick checks before opening the vial:
- Does the batch number on the COA match the batch number on the vial? Mismatches happen during packing; catch them early.
- Is the observed mass within tolerance? A 30 Da discrepancy on a 1,500 Da peptide often signals an oxidation product rather than the target.
- Is the purity sufficient for your experiment? A binding assay tolerates 95%; a receptor-occupancy quantification probably needs 98% or better.
Red flags
If a supplier cannot provide a COA, that is the signal. Other warning signs:
- One COA covers multiple batches with the same numbers — implies the data was not actually generated per batch
- HPLC purity quoted without a chromatogram or wavelength
- “≥95%” with no actual measured value — round numbers without raw data suggest the test was not run
- No mass spectrometry data, only purity — identity has not been confirmed
- No lab name or analyst on the document — accountability is missing
Where to get the COA for our peptides
Every batch we supply ships with a third-party HPLC and mass spectrometry Certificate. If you need a digital copy before purchase, use the chat bubble or our Contact form. For general questions about our quality control process, see the FAQ.
For in-vitro research use only. Not for human or veterinary consumption.