High-performance liquid chromatography is the workhorse method for assessing the purity of reference materials. Here is a brief primer on interpreting a report.
The chromatogram
Each peak represents a component eluting from the column at a characteristic retention time. The main peak corresponds to the target compound.
Area percent
Purity is typically reported as the area of the main peak divided by the total peak area, expressed as a percentage.
Why method matters
Column chemistry, gradient and detection wavelength all influence the result, which is why methods are reported alongside the figure.