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How to read a certificate of analysis

A certificate of analysis (COA) is the lab report for one batch of material. It is the only real evidence of what is in a vial, so it is worth knowing what a good one contains, and what a weak one leaves out.

1. 1

   Lot number

   The single most important line. A certificate describes one batch, and its lot number must match the lot printed on the vial in your hand. A certificate with no lot number, or one that doesn't match, tells you nothing about your material.

2. 2

   Purity by HPLC

   High-performance liquid chromatography separates the contents of a sample and measures each part. The result is given as a percentage: of everything detected, how much is the target compound. ≥99% means impurities make up 1% or less. Look for the chromatogram itself (the graph of peaks), not just a number.

3. 3

   Identity by mass spectrometry

   Purity says the sample is mostly one thing; mass spectrometry says what that thing is. It weighs the molecule and compares the measured mass to the expected molecular weight. A pure sample of the wrong compound would pass HPLC and fail here, which is why both tests matter.

4. 4

   Testing laboratory and date

   Who ran the tests and when. An independent laboratory, named on the certificate, is stronger evidence than an unnamed or in-house one. The test date should fall before the material was released for sale.

5. 5

   Appearance and form

   A short physical description, usually “white lyophilized powder”. It should match what you see in the vial.

6. 6

   Additional screens (when listed)

   Some certificates add bacterial endotoxin, heavy metals or net peptide content (how much of the powder's weight is peptide rather than salts and water). Count a screen as done only if its result is printed on the certificate for your lot.