HPLC Detectors High Performance Liquid Chromatography Detectors are devices that are used to sense each solute as it is eluted from a liquid chromatography column. Solutes do not modify the physical or chemical properties of a liquid nearly as much as solute vapors modify the properties of a gas. As a result, liquid chromatography detectors are three to four orders of magnitude less sensitive than gas chromatography detectors. Liquid chromatography detector have sensitivities (or minimum detectable concentration) that range from 10-6 gram per ml to about 10-9 gram per ml. in general, they have a linear response over about three orders of magnitude. There are two basic types of detector, the ‘bulk’ property detector and the solute property detector. The bulk property detector responds to changes in some physical property of the mobile phase, such as refractive index, or dielectric constant. They have maximum sensitivities of about 10-6 to 2 x 10-7 gram per ml. Solute property detectors respond to some property of the solute alone such as UV adsorption, fluorescence etc. They have maximum sensitivities of about 10-8 to 10-9 gram per ml. The most popular HPLC detector is probably the UV absorption detector in one of its various forms.