Detection occurs when the light is bent due to samples eluting from the column, and this is read as a disparity between the two channels. Fluorescent detectors measure the ability of a compound to absorb then re-emit light at given wavelengths. Each compound has a characteristic fluorescence. The excitation source passes through the flow-cell to a photodetector while a monochromator measures the emission wavelengths. It operates by detection of fluorescence associated with beta-particle ionization, and it is most popular in metabolite research.
Electrochemical detectors measure compounds that undergo oxidation or reduction reactions.
Usually accomplished by measuring gain or loss of electrons from migrating samples as they pass between electrodes at a given difference in electrical potential. The sample compound or molecule is ionized, it is passed through a mass analyzer, and the ion current is detected. An electron current or beam created under high electric potential is used to ionize the sample migrating off the column. Chemical Ionization - A less aggresive method which utilizes ionized gas to remove electrons from the compounds eluting from the column. However, when placed between poles of a strong magnet, the spins are aligned either parallel or anti-parallel to the magnetic field, with the parallel orientation favored since it is slightly lower in energy.