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Chromatography detectors designed to assess the individual molecules that come out (i.e., elute) from the chromatography column of a liquid and/or high-performance liquid chromatography (HPLC) system. These devices detect and measure the properties of the mobile phase (e.g., refractive index) and/or the characteristics of the sample constituents, such as fluorescence, ultraviolet absorption, or electrochemical changes. The detector types commonly found in the clinical laboratory are (1) photometers or spectrophotometers, which isolate a fixed wavelength (other wavelengths are made available by choice of filters) or use monochromators (e.g., diffraction gratings) of varying wavelengths; (2) fluorescence detectors (i.e., fluorometers), which are based on the ability of a molecule to emit light after it has been excited by light radiation and are more sensitive than photometers or spectrophotometers; (3) electrochemical detectors, which measure compounds that undergo either oxidation or reduction at an electrode surface; and (4) detectors based only on the charge of the component independently of the chemical structure (known as charged aerosol detectors). Additionally, liquid chromatography systems are often combined with and work together with mass spectrometers as detectors. Liquid chromatography detectors are mainly used in clinical laboratories as a component of chromatography systems intended to assess components in body fluids (including toxicology and endocrinology applications) or to assess other compounds.
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