Research guides · 9 min read
How to read a peptide Certificate of Analysis (COA)
What HPLC and mass spectrometry readings actually tell you, what to verify before purchase, and the red flags that distinguish a genuine COA from a marketing document.
A genuine certificate of analysis names the testing laboratory, the analysis date, the lot number and the method used. If any of those four are missing, the document is marketing, not analysis.
The HPLC chromatogram should show a dominant single peak with the area percentage stated. Mass spectrometry should confirm the observed molecular weight against the theoretical value for the sequence.
Cross-check the lot number on the COA against the lot printed on the vial label. Pooled COAs reused across batches are the most common failure in the research supply chain.