Detector in High Performance Liquid Chromatography

Detector

Detector records the relative concentrations of different components of the test sample with respect to their retention time. Retention time is the time taken by the compound to elute from the column. Retention time is calculated from the time of injection until the compound is eluted. Detection is based on several different physical principals. 

Those are UV absorption, fluorescence, radioactivity, IR absorption and electrochemical gradient. Depending on the characteristics of the mixture the physical principals will be different.