How to Read a Certificate of Analysis

A Certificate of Analysis is the single most important document attached to any research compound, and also the most commonly skimmed past. It exists to answer one question with evidence instead of a claim: is this vial what the label says it is, and how much of it is actually there.

Lot number and traceability

Every CoA should be tied to a specific lot number, not a general product line. This is what lets a single vial on your bench be traced back to a specific manufacturing and testing event. If a CoA has no lot reference, it isn't describing the vial in front of you — it's describing a product in general, which is a meaningfully weaker claim.

Purity percentage

Purity is reported as a percentage of the total peak area attributable to the target compound versus everything else in the sample — residual solvents, salts, synthesis byproducts, and related impurities. A number without a method attached (see below) is close to meaningless; the same sample can report differently depending on how it was measured.

Method: HPLC and mass spectrometry

High-performance liquid chromatography (HPLC) separates and quantifies compounds in a sample — this is where the purity percentage comes from. Mass spectrometry (LC-MS) confirms molecular identity by measuring mass-to-charge ratio, answering a different question: not how much, but is it actually the compound it claims to be. A rigorous CoA reports both, because purity of the wrong compound is not a useful result.

Testing lab and independence

The most reliable CoAs are issued by a third-party lab with no financial stake in the result — not an internal lab operated by the seller. Look for a named, independent laboratory, and treat self-issued or unnamed 'in-house tested' claims with proportional skepticism.

Every ALTR batch ships with a CoA that includes all of the above: lot number, HPLC purity, LC-MS identity confirmation, and the independent lab that ran the analysis. You can look up any current batch on our Lab Results page.