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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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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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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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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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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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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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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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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Images for Illustrating Spectrometers

Several of the posts in the Analytical Image and Video Exchange include schematic diagrams of spectrophotometers. Gathered here are jpeg files for the various components used to create these schematic diagrams. source shutter sample   blank   mirror   grating/monochromator … Continue reading

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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

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