What is HPLC?

How HPLC works

In HPLC a high-pressure pump pushes a liquid solvent — the mobile phase — through a steel column packed with small porous particles that form the stationary phase. The sample is injected into the flowing solvent and its components partition between the two phases, so each moves through the column at its own rate. As components leave the column they pass through a detector, commonly a UV–Visible absorbance detector or, increasingly, a mass spectrometer. The very small particles demand high pressure but yield narrow, well-separated peaks.

Columns, detectors and modes

The choice of stationary phase defines the separation mode. In reversed-phase HPLC — by far the most common — a non-polar stationary phase retains non-polar solutes, which are eluted with increasingly non-polar solvent.

Detectors are matched to the analytes: ultraviolet and diode-array detectors suit light-absorbing compounds, fluorescence detectors suit fluorescent ones, and mass-spectrometric detection (LC-MS) adds molecular identification. The time each compound takes to elute, its retention time, helps identify it against standards.

Uses in research

HPLC is a workhorse of analytical chemistry, biochemistry, and the pharmaceutical sciences. Researchers use it to check purity, measure concentrations, separate proteins and peptides, and characterise natural products and pollutants. Because retention times and peak areas depend on column, solvent, temperature, and flow rate, reproducible HPLC requires careful method documentation and calibration against reference standards — part of making analytical data comparable and reusable.