A Certificate of Analysis is the single most information-dense document a research peptide order comes with, and also the easiest to skim past without actually verifying anything. It's the analytical record for one specific production batch — what testing was run, and what the results were — and it exists so a receiving lab can confirm identity and purity before material enters a workflow.
The fields that matter
- Compound identity & sequence — confirms the material matches what was ordered, ideally down to the full amino acid sequence for peptide products.
- Measured purity — the analytical purity value, with the method used named explicitly (e.g. HPLC), not just a percentage sitting on its own.
- Molecular formula & mass — supports identity confirmation, typically established via mass spectrometry.
- Batch / lot number — the field that ties the entire document to the exact vial in your hand; this is non-negotiable.
- Test date — when the analysis was actually run, which matters for judging how much time has passed since testing relative to your storage conditions.
- Supplied form & storage — how the material was prepared (lyophilized powder, typically) and how it should be kept, consistent with our guide to storing research peptides.
- Testing laboratory — ideally identified, and ideally independent of the supplier; see third-party testing.
A quick walkthrough
Picture a COA for a vial of research-grade tirzepatide: it should state the sequence-derived molecular formula, a molecular weight matching that formula, an HPLC purity figure (e.g. 99.1%) with the column or method noted, a lot number that also appears on the vial's own label, and a test date within a reasonable window before shipment. If any one of those fields is missing — particularly the lot number — the document is not actually verifying the vial you're holding, regardless of how professional it looks.
Batch-specific beats generic
The single most important property of a COA is that it's tied to your lot. A generic specification sheet that could describe any batch a supplier has ever shipped tells you very little about what's actually in your vial. A batch-specific COA — lot number matching the vial in hand — is what supports genuine receiving inspection and recordkeeping, and it's the document worth asking for before you order, not after.
Red flags
- No analytical method named next to the purity figure.
- No batch/lot number, or one that doesn't match the vial received.
- A headline purity claim with no supporting document available at all.
- A COA that reads identically across multiple different product listings.
For the full framework this document fits into, see our guides on choosing a supplier and buying research peptides online.
Keeping COAs on file
Beyond the moment of receiving a shipment, a COA is a recordkeeping document a lab should retain for as long as the corresponding batch is in use. If a research result ever needs to be revisited or reproduced, having the original batch's identity and purity data on file — rather than relying on memory or a general product description — is what lets that batch be distinguished from any other lot of the same compound ordered before or after it.
Research Use Only. Supplied strictly for laboratory research and development — not for human or veterinary use, consumption, or any therapeutic or diagnostic purpose. This article is research education, not usage guidance.
See a third-party–tested compound: BPC-157 (batch COA available) →