A Certificate of Analysis (COA) is the document that proves what you bought is actually what the label says. It is generated by an analytical laboratory and contains the test results for a specific batch or lot of a peptide.
The first section typically lists identifying information: the peptide name or code, lot/batch number, manufacturing date, and specifications (such as target purity and mg per vial). Check that the lot number matches the one on your product vial.
The HPLC section is the most important. It shows the purity percentage, which represents the proportion of the sample that is the correct target peptide. Look for 98% or higher for research-grade material. The chromatogram should show one dominant peak.
The mass spectrometry (MS) section confirms molecular identity. The observed molecular weight should match the expected molecular weight for the target peptide sequence within a small margin of error (typically less than 1 dalton).
Additional sections may include sterility testing (should conform), bacterial endotoxin levels (should be below the specified limit, typically NMT 20 EU/mg), water content (should be low for lyophilized products), and appearance (typically described as white or off-white cake or powder).
Disclaimer: This article is for educational purposes only. All peptides are sold for laboratory research use only. Not for human consumption.