How to Read a Certificate of Analysis

A certificate of analysis (CoA) is a formal document that records the results of analytical testing carried out on a specific batch of a material. It is issued by the manufacturer or an accredited testing laboratory and accompanies the material as a record of its tested properties at the time of release. The CoA is one of the primary documents used to confirm that a received material matches its specification. The guidance below is factual and educational; it describes how to read a document, not how to use any material.

Material identity and description

The header of a CoA typically identifies the material by name, the internal catalogue or product reference, and the batch or lot number. These fields establish which material and which production batch the document applies to. Cross-checking the name and batch number against the label on the received vial is the first step in using the CoA, since a CoA for a different batch does not describe the material in hand.

Specification and results columns

Most CoAs present results in two parallel columns: one listing the specification (the requirement that must be met) and one listing the actual result measured for the batch. Reading both columns together shows whether the batch met each requirement. A result column entry of “≥99%” beside a specification of “≥98%” means the batch exceeded the specified requirement for that parameter.

Test parameters

The test parameters listed on a CoA vary by material type and the testing approach of the manufacturer, but commonly include appearance, identity confirmation, purity, and water or solvent content. Each parameter is defined, measured by a stated method, and compared to its specification. For research peptides, identity is often confirmed by mass spectrometry and purity by HPLC.

Identity tests confirm that the material is the compound it is stated to be. For peptides, mass spectrometry is widely used: the measured molecular weight is compared to the expected value calculated from the sequence. A result that matches the expected molecular weight supports the conclusion that the material has the correct identity. For background on how mass spectrometry works and what the result represents, see Understanding Mass Spectrometry.

Purity is typically measured by HPLC and reported as a percentage of the main peak area relative to the total. A specification such as “≥98% by HPLC” means the batch must show a main peak area of at least 98% under the stated chromatographic conditions. The CoA will show both the specification and the measured value, together with the analytical method reference. For a fuller explanation of what purity percentages represent, see Understanding Purity Percentages, and for how HPLC generates the data behind this figure, see Understanding HPLC Analysis.

A CoA typically carries a date of testing or date of issue, and a signature or approval from the person or function responsible for releasing the material. The date is relevant because it records when the testing was performed, not necessarily when the material was manufactured or when it will be used. Reviewing the date confirms the CoA applies to the batch in question at the time of testing.

A CoA confirms that the tested batch met its stated specification at the time of testing under the stated methods. It is a record of historical analytical results for a specific batch. It does not guarantee the condition of the material after receipt and storage, nor does it describe how the material will perform in any experiment. It is most informative when read alongside the material specification and the storage information provided with the material.

For how batch information links a CoA to a specific production event, see Research Material Batch Identification. For how specifications are structured and what each field means, see Understanding Research Material Specifications. For an overview of how analytical results on a CoA are generated in the first place, see Analytical Testing Workflow Overview. Our general approach to material quality and consistency is described on the Quality page.