How COAs and Batch Testing Work in Peptide Labs

A Certificate of Analysis (COA) is the primary document that validates the identity, purity, and quality of a research peptide batch. Understanding how to read and interpret a COA is an essential skill for any researcher working with these compounds.

HPLC Purity Testing

High-Performance Liquid Chromatography (HPLC) is the gold standard for measuring peptide purity. The technique separates compounds based on their interaction with a stationary phase, producing a chromatogram where each peak represents a distinct molecular species. A purity of ≥98% by HPLC means that at least 98% of the detected material corresponds to the target peptide, with the remaining 2% or less consisting of synthesis byproducts, truncated sequences, or other impurities.

Mass Spectrometry Verification

While HPLC confirms purity, mass spectrometry (MS) confirms identity. By measuring the mass-to-charge ratio of ionized molecules, MS can verify that the compound's molecular weight matches the theoretical value for the target peptide sequence. A reputable supplier will provide both HPLC and MS data on every COA.

Batch Numbers and Traceability

Each production batch receives a unique identifier that links the product to its specific COA. Researchers should always record the batch number when logging compound usage, enabling traceability if questions arise about data reproducibility.

Third-Party Testing

The most credible COAs come from independent, accredited analytical laboratories rather than in-house testing. Third-party verification removes conflicts of interest and provides an objective assessment of compound quality.

What to Look For

When reviewing a COA, verify the compound name and synonyms, molecular weight, purity percentage, testing methodology, batch number, and the testing laboratory's accreditation status. Any reputable supplier should make COAs readily available upon request or directly on their product pages.