What a Certificate of Analysis Documents

A certificate of analysis, usually shortened to COA, is the analytical record that accompanies a specific batch of material. It is not marketing collateral and it is not a general description of a product line. It is a dated statement of what a defined quantity of material was measured to be, by named methods, on a named date. Everything on it refers to one lot and nothing else.

The purpose of a COA is traceability. When material is later referenced in laboratory records, the COA is the artefact that connects the vial in front of you to a measurement someone actually performed. Without it, a purity figure is an assertion. With it, the figure is attached to a method, an instrument run, a date, and an identifier that can be quoted in your own documentation.

This is also why a COA has to be filed rather than skimmed. The value of the document appears months later, when a record needs to be reconciled and the only reliable link between an entry in a notebook and the material it refers to is a batch identifier.

Layouts differ between laboratories, but the substantive content is consistent. A complete certificate records the following.

• Material name as supplied, and the catalogue reference it corresponds to.
• Batch or lot identifier — the primary key for every other field on the sheet.
• Quantity and presentation, including fill volume and vial format.
• Appearance, described as observed rather than as expected.
• Identity confirmation, with the method used to establish it.
• Purity result, expressed as a percentage against the method that produced it.
• Analytical methods applied, typically HPLC and mass spectrometry.
• Date of analysis, and where relevant the date of manufacture.
• Storage condition under which the material was held and should continue to be held.
• The name of the laboratory that performed the testing.

These two lines answer different questions and are frequently conflated. Identity confirmation answers whether the material is the compound named on the label. Purity confirmation answers what proportion of the material present is that compound rather than process-related impurities, residual solvent, or degradation products.

A sample can be highly pure and still be misidentified, and it can be correctly identified while carrying a significant impurity fraction. This is why the two determinations are made by different methods and reported separately. The methodology behind each is covered in more detail in how peptide purity is determined.

A batch identifier is assigned to a defined production quantity that was processed together under the same conditions. Every vial filled from that quantity carries the same identifier, and every analytical result generated from a sample of it is recorded against that identifier. When the next quantity is produced, it receives a new identifier, even if the material, the process, and the specification are unchanged.

The identifier appears in three places that should agree: the vial label, the outer packaging or packing list, and the COA itself. If any of the three disagree, the documentation chain is broken and the material should be set aside rather than entered into a record.

Analytical results describe the sample that was tested, not the catalogue entry it was sold under. Two lots of the same compound, made to the same specification, will still return slightly different numbers because they are different physical material measured on different days. Reporting a single figure for an entire product line would therefore be a statement about nothing measurable.

A specification is a threshold the material must meet. A COA result is the measurement obtained for one lot. The two are related but are not the same statement.

Checks on arrival are quick and are best done before the packaging is discarded, since the packaging carries information that is difficult to reconstruct afterwards.

• Confirm the batch identifier on the vial matches the COA supplied with the shipment.
• Confirm the material name and fill volume on the label match the order and the certificate.
• Compare the observed appearance of the vial against the appearance recorded on the COA.
• Confirm the vial seal is intact and the closure has not been disturbed.
• Check the date of analysis is present and legible.
• Confirm the shipment arrived within its stated cold-chain condition, as described in cold-chain handling and transit.

A COA is only useful if it can be retrieved. The practical approach is to file it under the batch identifier rather than the compound name, because the identifier is unique and the compound name is not. Record the date of receipt alongside it, since the COA states when the material was analysed but not when it entered your custody, and that gap belongs in your records rather than the supplier's.

Where an institution maintains a materials register, the minimum useful entry is the batch identifier, the date of receipt, the storage location assigned, and a reference to the stored copy of the certificate. Storage conditions after receipt are the purchaser's responsibility and are covered separately in storage and stability of pre-mixed solutions.

Retain the certificate for as long as any record referring to that batch is retained. Discarding the COA while keeping the notebook entry leaves an unverifiable reference behind, which is precisely the situation the document exists to prevent.