How to read a Certificate of Analysis

A Certificate of Analysis, usually abbreviated COA, is a document that reports the results of analytical testing performed on a specific batch of material. It is the primary record a qualified account uses to confirm that a supplied peptide matches its stated identity and specification. A COA is tied to a particular lot, which means the values it reports describe that lot and not the product in the abstract. Reading one well is mostly a matter of knowing what each section is measuring and what a result is being compared against.

Header and lot traceability

The top of a COA typically identifies the material by name and often by sequence or molecular formula, and it records the lot or batch number and the date of analysis. The lot number is the thread that ties the certificate to a physical batch and to the batch records behind it. If a question arises later, the lot number is what allows the analysis, the documentation, and the material to be reconciled. Confirming that the lot number on the certificate matches the lot number on the material label is the first step in reading any COA.

Identity

Identity tests confirm that the material is the molecule it claims to be. This is commonly established by mass spectrometry, and sometimes supported by other analyses. The certificate states the expected value and the observed value so the two can be compared directly.

Purity by HPLC

Purity is most often reported by high-performance liquid chromatography, or HPLC. The technique separates a sample into its components as they pass through a column, and the resulting chromatogram shows peaks whose relative areas are used to estimate purity. Purity is expressed as a percentage — the proportion of the total peak area attributed to the target peptide. A specification such as "≥ 98%" means the lot is expected to meet or exceed that threshold, and the reported result states what was actually measured. It is worth noting that a purity percentage describes the chromatographic profile; it is a different quantity from net peptide content, which accounts for non-peptide mass such as bound water and counter-ions.

Molecular mass by MS

Mass spectrometry (MS) measures the mass-to-charge ratio of ionized molecules, allowing the molecular weight of the peptide to be determined and compared with the value expected from the sequence. Agreement between the observed and expected mass is strong evidence that the correct molecule is present. The COA usually lists both the theoretical mass and the observed mass.

Appearance, water, and related fields

• Appearance — a description of the physical material, for a lyophilized peptide typically a white to off-white powder.
• Water content — often measured by Karl Fischer titration, reporting residual moisture as a percentage.
• Net peptide content — the fraction of the mass that is peptide, distinct from chromatographic purity.
• Counter-ion or salt form — noted where relevant, since it affects the reported mass.
• Solubility — a physical property sometimes recorded for reference.

Putting it together

Reading a COA is a systematic comparison: confirm the lot matches the material, then work down the rows checking each result against its specification. Identity confirms the molecule, purity and mass describe its quality and confirm its structure, and appearance and water content describe the physical form. Because every value is anchored to a lot number, the certificate is only meaningful when read alongside the batch it documents — which is why lot-level traceability underpins the entire record.