What a COA is for
A certificate of analysis is the document that ties a specific batch of material to a specific set of test results. Its value is entirely in that link. A purity figure with no batch identifier describes nothing you can verify against the vial in your hand.
This page is reference information for laboratory personnel handling research materials. It contains no medical, dosing, or human-use guidance of any kind.
The four fields that matter
- Batch or lot number — must match the number printed on the vial label exactly
- HPLC purity — the percentage of the sample that is the target peptide, typically reported to one decimal place
- Mass spectrometry identity — confirms the observed molecular weight matches the theoretical weight for the sequence
- Test date — tells you when the material was characterised, not when it was shipped
Reading the HPLC result
HPLC separates the sample into its components and reports the target peak as a percentage of total peak area. A result of 99.5% means the target peptide accounts for 99.5% of what the detector saw. The remaining fraction is typically synthesis-related impurities and residual solvent.
A chromatogram attached to the certificate is stronger evidence than a bare number, because it shows the peak shape and whether the remaining area is a single co-eluting impurity or scattered noise.
Reading the mass spectrometry result
The mass spectrometry section reports the observed molecular weight against the theoretical weight calculated from the sequence. These should agree closely. Identity and purity answer different questions: mass spec says the material is the right compound, HPLC says how much of the sample is that compound. A certificate reporting only one of the two is incomplete.
Warning signs
- No batch number, or a batch number that does not appear on the vial label
- A test date that predates the lot's manufacture date
- Purity reported without a method — a percentage with no HPLC reference is unverifiable
- The same certificate reused across visibly different lots
- An image so compressed that the values and peaks cannot be read
Verifying before you order
The strongest position for a buyer is being able to read the documentation before committing to a purchase. Obsidian Peptides publishes full certificates for tested lots on the COA page, with batch number, purity, and test date visible in full resolution rather than supplied on request after checkout.