Identity Testing vs. Purity Testing

Identity testing asks: is this material what it is labelled to be? Purity testing asks: of the material present, how much is the target compound versus everything else? A material can pass one and not the other.

Confusing the two leads to over-confidence. A strong identity assessment does not, on its own, tell you how pure a material is, and a high purity figure does not confirm identity if the wrong reference was used.

Good documentation pairs the two. Identity assessment establishes what the material is; purity analysis quantifies how much of it is the target compound. Together they give a fuller picture than either alone.

When reviewing documentation, look for both — and for a clear statement of the methods behind each.