How to Read a Peptide COA: A Complete Walkthrough

The header: identity and lot

The top of a certificate should state the compound name, the sequence or at minimum the molecular formula, the theoretical molecular weight, the lot number, the date of analysis and the testing laboratory. If the lot number on the document does not match the label on the vial in your hand, the document tells you nothing about that vial.

A certificate with no lot number is a marketing sheet, not a certificate.

The purity section

Peptide purity is often reported as area percent from a reverse-phase HPLC run at a stated wavelength. That value describes the target peak relative to the other peaks detected under the stated method conditions; it is not the peptide's percentage of total vial mass. The chromatogram, wavelength, integration and reporting threshold provide essential context for the number.

A chromatogram can reveal separated peptide-related impurities, but no single chromatographic method detects every possible impurity. ICH Q2(R2) treats specificity or selectivity as a characteristic that must be demonstrated for the intended analytical procedure, while the peptide-impurity literature describes deletion sequences, oxidation, deamidation, epimerization and aggregation as distinct analytical challenges.

The identity section

Identity testing asks whether the principal material is consistent with the named compound. Mass spectrometry can compare observed mass-to-charge data with the expected molecular mass; chromatographic retention-time matching can compare a sample with a qualified reference standard. A report should state which identity method was actually used.

A matching molecular mass is useful identity evidence, but mass alone may not distinguish structural isomers or sequence variants with the same nominal mass. Conversely, an HPLC area-percent result describes chromatographic purity under that method and does not, by itself, establish molecular identity. Orthogonal methods reduce these method-specific blind spots.

Net peptide content and residuals

Net peptide content and HPLC area-percent purity answer different questions. Net content estimates how much peptide is present, while the gross material can also include counter-ions and water. The report should name the assay used rather than asking the reader to infer net content from chromatographic purity.

Counter-ion identity and quantity can affect mass balance and some analytical or biological experiments. Water, residual solvents, endotoxin and sterility are separate attributes that require their own suitable methods; none can be inferred from an HPLC purity value or a mass spectrum.

• Compound name, sequence and theoretical mass
• Matching lot number and analysis date
• HPLC chromatogram with purity as area percent
• Identity method and result, such as qualified retention-time comparison or mass spectrometry
• Net peptide content and assay method, when relevant
• Testing laboratory identified by name

Red flags

Material concerns include a missing lot number, an unidentified laboratory, absent method information, a result without the underlying trace where a trace is expected, or a certificate reused for a different lot. These observations should prompt questions rather than assumptions about what was tested.

Novanta's Certifications page publishes the reports currently available for specific listed lots. Read each report for its actual methods and results: the posted set is not uniform and does not include peptide mass-spectrometry results. It should not be summarized as a blanket 99%+ claim. ICP-MS heavy-metals screening, where reported, is not peptide molecular-identity testing.