Laboratory reference guide

How to read a peptide certificate of analysis

How to distinguish mass evidence, chromatographic purity, content, microbiological results, elemental impurities and lot traceability on a peptide COA.

Research use only. The information below concerns laboratory reference materials for in-vitro research and makes no medical, therapeutic, diagnostic, cosmetic or performance claims.

A certificate of analysis (COA) records what a laboratory measured for one specific lot of a reference material. Read the lot number first, then verify which methods, results, units, limits and release decision are actually present in the source report.

Mass-related identity evidence (LC-MS / ESI-MS)

When mass-spectrometry evidence is present, the observed mass can be compared with the theoretical molecular weight. Agreement supports the expected molecular mass, but it does not by itself establish the complete sequence or distinguish every isomer. Identity must not be inferred from an HPLC purity result alone.

Chromatographic purity (RP-HPLC)

Reversed-phase HPLC reports the area-percent of the main peak under the stated method. It describes chromatographic purity under those conditions, not peptide identity, mass fraction or net peptide content.

Net peptide content, water and counterion

Net peptide content, water (for example by Karl Fischer) and the counterion or salt form (for example acetate or trifluoroacetate) affect how the supplied mass relates to the amount of peptide — important when calculating stock concentrations.

Other evidence classes are not interchangeable

Endotoxin, bioburden, sterility and elemental-impurity results answer different questions. A low endotoxin result does not establish sterility; a bioburden count is not a sterility test; a sterility result applies only to the tested sample, method and stated conditions; and elemental-impurity results do not establish organic purity or identity. Read each result together with its method, units or decision limit, sample reference and disposition.

Lot traceability

Always check that the report lot number matches the vial. A COA is meaningful only for the exact lot it describes; the COA Vault keeps current and archived records separate.

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