Laboratory glossary
Certificate of analysis: reading a batch document
A results document for an identified sample or batch; each determination has its own method and scope.
Source editorial review:
The distinction that matters
A certificate for the right compound but a different batch does not automatically document the received vial.
What a certificate reports
A certificate of analysis, or COA, records analytical determinations for a particular batch. It does not characterize the compound in the abstract; it describes only the batch identified in the document.
A research peptide COA commonly addresses identity, often by comparing electrospray mass-spectrometry results with the calculated mass of the declared sequence; reversed-phase HPLC purity; physical appearance; and declared net vial content. Exact methods, results and additional parameters vary by compound and should be checked against its documentation.
- Batch number links the document to the physical material received.
- Identity reports evidence that the material corresponds to the declared sequence.
- Chromatographic purity expresses principal-peak area relative to total integrated area under the method.
- Analysis date records when testing occurred, which is not necessarily the packaging date.
- Method identifies the technique and conditions behind each result.
Why it matters for research material
In a research-only catalog, the COA supplies batch-specific analytical evidence behind a product description. The catalog explains the reference compound; the batch document reports the tested material associated with the received vial.
The batch number on the vial must match the COA. A document for another batch does not characterize the material received. This simple traceability check is easily overlooked.
Certificates also help compare acquisitions. Batches of the same compound can differ within specification. Without batch results, it becomes harder to distinguish an experimental change from a change in starting material.
Read it without extending its scope
A COA reports what the stated methods measured. A high HPLC area percentage means the main peak contributed that fraction of integrated signal under those separation and detection conditions. It does not exclude unresolved species or impurities invisible to the detector, and it is not automatically a mass fraction.
Identity confirmation by mass establishes correspondence with an expected molecular mass. Distinguishing isomers or equal-mass analogs requires additional determinations, which should be stated if performed.
The COA characterizes the material at analysis. It does not establish what happened afterward during transport, moisture exposure or reconstitution. Preserve it together with receipt and handling records to maintain the documentary chain.
Common confusion
A specification describes acceptance criteria prospectively, such as minimum chromatographic purity and identity requirements. A COA reports actual results retrospectively for one batch. The specification sets the threshold; the COA gives the result. A document lacking a batch number and measured results is not a batch COA merely because of its title. A certificate of conformity is also different: it declares conformity without necessarily reporting determinations or attaching chromatograms and spectra.
How to record it
Issuer, sample, batch, date, methods, results, units and attachments.