How to Read a Certificate of Analysis (COA)

A certificate of analysis is the lab report that comes with a batch of peptide. It is the main evidence you have that the vial contains what the label says. Many COAs look official and say very little, so it pays to know what to look for.

The header: who tested what

Start at the top. A useful COA names:

• The testing lab, with an address or website you can look up
• The compound, spelled the same way as the product label
• A batch or lot number that matches the number on your vial
• The test date, ideally recent relative to when the batch was made

If the lot number on the COA doesn't match the vial, the report tells you nothing about your vial.

Identity: is it the right molecule?

Identity is usually confirmed by mass spectrometry (MS). The report should list the expected molecular weight and the measured one. They should agree closely. A COA that reports purity but never confirms identity has skipped the most basic question.

Purity: how much of it is the right molecule?

Purity is usually measured by HPLC, reported as a percentage of the total peak area. A good report includes the chromatogram itself, not just the number. Look for one dominant peak. Several sizeable side peaks mean impurities such as truncated sequences or breakdown products.

Purity is not the same as content. A vial can be 99% pure and still hold less material than the label states.

Content or net peptide amount

Some labs also report how many milligrams of peptide are actually in the vial. This is the number that tells you whether the fill matches the label. Not every COA includes it, and it is worth asking for.

Red flags

• No lab name, or a lab you can't find anywhere
• No lot number, or one that doesn't match your vial
• A purity number with no chromatogram
• The same COA reused across many batches or dates
• Edits, mismatched fonts or a blurry screenshot instead of a PDF

Checking it independently

The strongest check is a test you commission yourself from an independent lab, using a vial from the batch you received. Post the results in Quality so other members can compare batches from the same vendor.

For research use only. Nothing here is medical advice.