Certificates of analysis

How to read a certificate

Lot

The batch identifier. Every vial from one synthesis and fill run shares it, and it is printed on the vial label. It is the only reliable way to tie a physical vial to a specific test result.

Report

What the document measures. Most are purity tests, but the archive also holds endotoxin, heavy-metal, microbial and content/identity reports. They answer different questions about the same lot, so a report that states no purity figure is not an incomplete purity test — it was never one.

Purity

The proportion of the sample that is the named compound, as measured by the stated method. Anything below the stated figure is impurity, which may be related peptides, residual solvent, or water. Shown only on a purity report; the other report types state their own analytes instead.

Labeled vs. actual

The label claim next to the measured content. Fill processes overshoot slightly by design, so actual content usually exceeds the label. Publishing both is how you show the label is not the only number that was checked.

Method

How the measurement was made. HPLC separates the sample into its components and quantifies each; MS confirms molecular identity by mass. A purity figure with no stated method is not a result.

Lab

Which laboratory ran the test. An in-house figure and an independent third-party figure are not the same claim, and a certificate that does not name the lab is not verifiable.

Test date

When the analysis was performed. Read it against the lot, not the order — a certificate predating the batch it claims to describe is a red flag.