A Certificate of Analysis (COA) is the primary document that accompanies a research-grade peptide batch. It records identity, purity, and the analytical methods used to characterise the material. Understanding each field on a COA is essential for anyone working with reference materials in a laboratory context.
Header block: product, batch, and dates
The header identifies exactly which material the certificate describes. It should always list the product name, the manufacturer's batch or lot number, the manufacture date, and a retest or expiry date. If any of these fields are missing, the document is incomplete and cannot be tied back to a specific physical sample.
- Product name and CAS or sequence identifier where applicable
- Unique batch / lot number that matches the vial label
- Manufacture date and recommended retest date
- Net fill weight and physical form (lyophilised powder, solution)
Identity confirmation
The identity section confirms the substance in the vial is what the label claims. For peptides, mass spectrometry (typically ESI-MS or MALDI-TOF) is used to match the observed molecular mass to the theoretical mass of the sequence. A well-formed COA reports both values and the delta between them.
Purity and impurity profile
Purity is normally expressed as an HPLC area-percent value at a defined wavelength (commonly 214 nm for peptide bonds). The COA should list the column, mobile phase, gradient, and detection wavelength so the result is reproducible. Related impurities that exceed a reporting threshold are itemised individually.
Physical and residual tests
Additional fields cover appearance, solubility, water content (Karl Fischer), residual solvents, and acetate or TFA counter-ion content. These are not always requested but appear on more complete certificates and matter for reproducibility across studies.
Authorisation
A COA closes with the name, title, and signature of the analyst or QC officer who released the batch, along with the date of release. Without this authorisation block the document is a draft, not a certificate.