A Certificate of Analysis is the paperwork that turns a vial into a documented sample. Every field on the sheet answers a specific question about what is inside. Read it in that order — compound, batch, method, identity, purity — and you get a full answer about what you are about to reconstitute. Skim it, and you get a decorative sheet that just looks technical.
Compound and Batch
The compound name should exactly match what is on the vial label. Any variant, salt form, or modifier (acetate salt, w/o DAC, LR3, etc.) belongs on both surfaces or neither. The batch number is the audit trail — every batch runs through the same production and QC cycle, and its results are unique to that batch. A COA that lists "batch: current" or omits the batch number entirely is not a COA at all; it is marketing that borrowed the format.
Method
"HPLC / MS" tells you both the quantitative purity assay and the identity confirmation were performed. HPLC alone measures how much of the sample is a single dominant species; MS alone confirms the identity of that species. Together they answer "how much" and "what" — either one alone leaves a gap the other one closes.
Identity
Identity: Confirmed means the mass spectrum shows a peak matching the expected molecular weight of the compound within instrument tolerance. If a peptide is supposed to weigh 3,367.94 Da and the ESI-MS spectrum shows a peak at 3,367.9 Da, identity is confirmed. If a COA reports purity without also confirming identity, the purity number is meaningless — 99% of an unknown substance is still 99% unknown.
Purity
Purity is calculated from the HPLC chromatogram: the area of the target peak divided by the total area of all peaks, expressed as a percentage. Research-grade peptides typically report ≥ 98%. The number itself matters less than the method that produced it — a purity claim without a chromatogram or a stated method is a claim, not a measurement.
The lines worth scrutinizing
- Batch number matches your vial. A COA is only valid for the batch it names.
- Both HPLC and MS are listed. Purity without identity is a half-answer.
- Date of analysis is recent. Peptides can degrade over time; an old COA does not certify a currently-shipping vial.
- The lab that ran the assay is named. Independent third-party analysis is the standard; a sheet with no signatory is a self-report.
At AminoVita Research we publish the COA for every batch directly on the site. If you can't find one for the batch printed on your vial, that is the first thing to flag — not the value on any field.