What an HPLC purity figure means (and what it does not)

What the number describes

A high performance liquid chromatography purity figure expresses the area of the main peak as a proportion of total detected peak area, under the specific column, gradient, detector and wavelength recorded on the report.

Two laboratories running different methods can report different figures for the same material. A purity figure without its method is not interpretable.

What the number does not describe

Purity says nothing about sterility, endotoxin load, residual solvents, heavy metals, water content or counter-ion content unless those tests were performed and reported separately.

A purity figure is not a safety assessment and is not evidence that a material is suitable for any particular application.

Reading a figure honestly

Match the figure to the batch printed on the physical unit, check the test date, and check that the laboratory is named. Where any of those are absent, treat the figure as unevidenced.