HPLC detectors fall into two main categories: universal or selective. Universal detectors typically measure a bulk property (e.g., refractive index) by measuring a difference of a physical property between the mobile phase and mobile phase with solute while selective detectors measure a solute property (e.g., UV-Vis absorbance) by simply responding to the physical or chemical property of the solute. HPLC most commonly uses a UV-Vis absorbance detector, however, a wide range of other chromatography detectors can be used. A universal detector that complements UV-Vis absorbance detection is the Charged aerosol detector (CAD).
Refractive index detectors are commonly used in HPLC. This detector provides readings by measuring the changes in the refractive index of the eluent as it moves through the flow cell. In certain cases, it is possible to use multiple detectors, for example, LCMS normally combines UV-Vis with a mass spectrometer.