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Tag Archives: chromatography
Ion-Exchange Chromatography
In ion-exchange chromatography (IEC) the stationary phase is a cross-linked polymer resin, usually divinylbenzene cross-linked polystyrene, with covalently attached ionic functional groups. As shown here for a styrene–divinylbenzene co-polymer modified for use as an ion-exchange resin, the ion-exchange sites—indicated here by … Continue reading
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
Posted in Illustration
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
Posted in Illustration
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
Posted in Illustration
Tagged chromatography, detector, fluorescence, HPLC, liquid chromatography, separation, UV/Vis
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Loop Injector for HPLC
The operating pressure of an HPLC is sufficiently high that we cannot inject the sample into the mobile phase by inserting a syringe through a septum (as we can do in gas chromatography). Instead, we inject the sample using a … Continue reading
Posted in Illustration
Tagged chromatography, HPLC, instrument, liquid chromatography, loop injector, separation
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HPLC Pumps
A typical HPLC includes between 1–4 reservoirs for mobile phase solvents. The mobile phase solvents are pulled from their reservoirs by the action of one or more pumps. Shown here is a close-up view of an instrument with two pumps, each … Continue reading
Posted in Photo
Tagged chromatography, HPLC, instrument, liquid chromatography, pump, separation
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Gradient Elution Separation of Flavonoid Mixture
The illustration below shows the gradient elution separation of a mixture of flavonoids. Mobile phase A is an aqueous solution of 0.1% formic acid and mobile phase B is 0.1% formic acid in acetonitrile. The initial mobile phase is 98% … Continue reading
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Tagged chromatography, gradient elution, HPLC, liquid chromatography, separation
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Using a Solvent Triangle to Optimize an HPLC Separation
One strategy for finding the best mobile phase for an HPLC separation is to use the solvent triangle, which allows us to explore a broad range of mobile phases with just seven experiments. We begin by adjusting the amount of acetonitrile … Continue reading
Posted in Illustration
Tagged chromatography, HPLC, liquid chromatography, optimization, separation, solvent triangle
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HPLC Column
The most common type of HPLC column is a stainless steel tube with an internal diameter between 2.1 mm and 4.6 mm and a length between 30 mm and 300 mm. The column is packed with 3–10 μm porous silica particles … Continue reading
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Tagged chromatography, column, HPLC, liquid chromatography, separation
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HPLC Instrumentation
The photo below shows an example of a typical HPLC instrument with insets showing close-up views of the pumps that move the mobile phase through the system, and the plumbing used to inject the sample into the mobile phase. This particular instrument … Continue reading
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Tagged chromatography, HPLC, instrument, liquid chromatography, loop injector, pump, separation
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