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Tag Archives: detector
UV/Vis Detectors for Capillary Electrophoresis
Most of the detectors used in HPLC also find use in capillary electrophoresis. Among the more common detectors are those based on the absorption of UV/Vis radiation, fluorescence, conductivity, amperometry, and mass spectrometry. Whenever possible, detection is done “on-column” before … Continue reading
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Tagged capillary electrophoresis, detector, electrophoresis, separation, UV/Vis
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LC-MS Detection
The figure below provides a block diagram of a typical liquid chromatography-mass spectrometer (LS–MS) instrument. As illustrated here, a three component mixture is injected onto the HPLC. When component A elutes from the column, it enters the MS ion source and ionizes … Continue reading
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Tagged chromatography, detector, HPLC, LC-MS, liquid chromatography, MS, separation
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Electrochemical Detector for HPLC Separations
Another common group of HPLC detectors are based on electrochemical measurements such as amperometry, voltammetry, coulometry, and conductivity. The illustration below, for example, shows an amperometric flow cell. Effluent from the column passes over the working electrode, which is held … Continue reading
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Tagged chromatography, detector, electrochemical detector, HPLC, liquid chromatography, separation
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Absorbance and Fluorescence Detection for HPLC Separations
One popular HPLC detector takes advantage of an analyte’s UV/Vis absorption spectrum. These detectors range from simple designs, in which the analytical wavelength is selected using appropriate filters, to a modified spectrophotometer in which the sample compartment includes a flow … Continue reading
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Tagged chromatography, detector, fluorescence, HPLC, liquid chromatography, separation, UV/Vis
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GC-MS
The figure below provides a block diagram of a typical gas chromatography-mass spectrometer (GC–MS) instrument. As illustrated here, a three component mixture enters the GC. When component A elutes from the column, it enters the MS ion source and ionizes to form … Continue reading
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Tagged chromatography, detector, gas chromatography, GC, GC-MS, mass spectrometry, separation
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Electron Capture Detector
Shown here is a schematic diagram of electron capture detector (ECD) for gas chromatography. The detector consists of a β-emitter, such as 63Ni. The emitted electrons ionize the mobile phase, which is usually N2, generating a standing current between a … Continue reading
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Tagged chromatography, detector, electron capture, GC, separation
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Flame Ionization Detector
The schematic diagram below shows a flame ionization detector for gas chromatography. The eluent from the column mixes with H2 and is burned in the presence of excess air. Combustion of organic analytes produces a flame containing electrons and organic … Continue reading
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Tagged chromatography, detector, flame ionization, gas chromatography, GC, separation
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Thermal Conductivity Detector
One of the earliest gas chromatography detectors takes advantage of the mobile phase’s thermal conductivity. As the mobile phase exits the column it passes over a tungsten-rhenium wire filament (see figure below). The filament’s electrical resistance depends on its temperature, … Continue reading
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Tagged chromatography, detector, gas chromatography, GC, separation, thermal conductivity
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Photomultiplier Detector
A photomultiplier contains a photosensitive surface that absorbs radiation in the ultraviolet, visible, or near IR, producing an electrical current proportional to the number of photons reaching the photomultiplier. As shown here, a photon strikes the photoemissive cathode producing electrons, which … Continue reading