How to read a Certificate of Analysis

A Certificate of Analysis is the analytical record for a single manufactured lot. It is produced by an accredited laboratory after the batch is synthesized and lyophilized, and it travels with that lot for its entire life. Reading one well is the difference between trusting a number and verifying it.

Every COA opens with the sample identity and the lot number. Before you read anything else, confirm that lot number matches the one printed on your vial — a COA for a different lot tells you nothing about the material in front of you.

What each line means

Identity confirms the molecule is what the label says. It is typically established by mass spectrometry, where the measured mass is compared against the theoretical mass of the target sequence. A match within the instrument's tolerance is the evidence the sequence is correct.

Purity is the proportion of the target compound relative to related impurities, measured by reverse-phase HPLC and reported at a fixed detection wavelength. The chromatogram behind the number matters: a single dominant peak with small, well-resolved impurities is what a high-purity result should look like.

Net content verifies the vial holds the stated mass within tolerance. Endotoxin (by LAL), heavy metals, and appearance round out a full panel — each an independent, separately reportable test. When every line passes, the lot is cleared for release.

A purity percentage without a chromatogram is a claim; with one, it is a measurement.