Certificate of Analysis: How to Read Your COA

What Is a Certificate of Analysis?

A Certificate of Analysis (COA) is a quality document provided by the peptide manufacturer that summarizes the analytical testing results for a specific batch of peptide. The COA serves as the primary quality assurance record and provides researchers with the data needed to assess whether a peptide meets the specifications required for their application. A well-prepared COA typically includes the peptide sequence, molecular weight, purity data, mass spectrometry results, lot number, and storage recommendations.

Key Sections of a Peptide COA

The most critical sections of a COA include the HPLC purity analysis, which reports chromatographic purity as a percentage, and the mass spectrometry data, which confirms that the observed molecular weight matches the theoretical value. Additional quality metrics may include peptide content (net peptide weight as a percentage of total weight, accounting for moisture, salts, and counterions), appearance description, solubility information, and amino acid analysis results. The lot or batch number is essential for traceability, ensuring that the specific vial received can be linked back to the original synthesis and quality control records.

Using COA Data to Ensure Experimental Accuracy

Researchers should review the COA carefully before beginning experiments. The peptide content value is particularly important for dose-dependent studies, as the gross weight on the vial label includes counterions and residual moisture. For example, if a vial contains 5 mg gross weight with a peptide content of 80%, the actual peptide mass is 4 mg, and concentrations should be calculated accordingly. Any discrepancy between the observed and expected molecular weight should be investigated, as it may indicate sequence errors or chemical modifications. Retaining COA documents for all peptide lots used in a study supports data integrity and facilitates reproducibility when publishing research findings.