A chromatographic detector can be dened in a very broad way as any device that locates, in the dimensions of space or time, the positions of the components of a mixture that has been subjected to some form of chromatography, thus allowing an appreciation of the separation that has been attained. Such a broad denition allows for many types of detectors, but for our purposes the denition can be tightened to allow only such detectors as can give a measurable response to the concentration of analyte in the eluant from an HPLC column.