Physical Principals for Detecting Compounds in High Performance Liquid Chromatography

In HPLC the compounds are detected by the section detector. Detection is based on different physical principals. These are UV absorption, fluorescence, radioactivity, IR absorption and electrochemical gradient.

Detection by UV absorption is mainly based upon the ultraviolet-visible spectroscopy. Some compounds can absorb or reflect light which is in between the UV spectral region. Such compounds are detected through UV absorption spectroscopy. The compounds absorb light and the molecules of these compounds then undergo electronic transitions. This happens when these molecules contain non bonding electrons. These non bonding electrons can absorb energy in the spectrum of UV or visible light to excite these electrons to higher energy states.

During electronic transitions of some compounds they undergo fluorescence. Fluorescence is a type of electromagnetic radiation. Also there are radioactive compounds which can be detected by relevant radioactive detectors.

IR absorption deals with the infrared region of the electromagnetic spectrum. IR is a light with a longer wave length and lower frequency than visible light. If molecules tend to emit light in this region the IR spectrometer can detect these compounds.