How to Read a Peptide Certificate of Analysis (COA)

A Certificate of Analysis (COA) is the primary quality document accompanying a research peptide batch. It links the material in your vial to analytical results from an independent or in-house laboratory. Knowing how to read a COA helps you assess suitability for demanding assays and satisfies internal quality reviews.

Key fields on every COA

• Product name and catalogue reference — must match your order.
• Batch or lot number — unique to the manufacturing run.
• Purity — typically reported as area percent by HPLC at a stated wavelength.
• Identity confirmation — often MALDI-TOF or LC-MS showing expected molecular mass.
• Appearance — lyophilised powder colour and form.
• Test date and laboratory name — traceability for audits.

Interpreting purity

Purity of 99% or above is common for research-grade peptides, but the number alone is not the whole story. Review the chromatogram for unexpected peaks that might indicate deletion sequences, oxidised variants, or residual reagents. Peptides EU provides batch-specific COAs from independent testing where applicable — including Janoshik Analytical reports for many compounds.

Why batch specificity matters

Generic “representative” COAs — not tied to the batch you received — offer limited value. Reproducible science depends on documenting exactly which material was used. Always archive the COA that matches your vial label and cite the batch number in lab notebooks and publications where required.

Browse verified test reports on our homepage quality section. Research use only — COAs support laboratory qualification, not clinical use.