Research Library
How to read an HPLC chromatogram
A plain-language guide to peaks, retention time and peak area, and how a purity percentage is calculated from a chromatogram.
What the chart shows
An HPLC chromatogram plots detector response against time. Each component that separates from the sample appears as a peak as it leaves the column.
Retention time is the point at which a peak appears. Under the same method and conditions, a given compound elutes at a consistent retention time.
Peak area and purity
The area under each peak relates to how much of that component the detector saw. Purity is commonly reported as the main peak's area as a percentage of the total area of all detected peaks.
Because it is a relative measure, the result depends on the detection wavelength and the method used. Always read the method details alongside the figure.
Things to check
Confirm the batch number, testing date and method on the report. Small additional peaks are normal and represent related substances or impurities detected at that wavelength.