Explore resources, experiments, and teaching materials shared by the analytical sciences community.
Another approach to separating neutral species is capillary electrochromatography, CEC. In CEC the capillary tubing is packed with 1.5–3 μm particles coated with a bonded stationary phase. Neutral species separate based on […]
One limitation to capillary electrophoresis is its inability to separate neutral species. Micellar electrokinetic capillary chromatography, or MEKC, overcomes this limitation by adding a surfactant, such as sodium dodecylsulfate (a) to the […]
We can reverse the direction of electroosmotic flow in capillary electrophoresis by adding an alkylammonium salt to the buffer solution. As shown in (b), the positively charged end of the alkyl ammonium […]
When a analyte’s concentration is too small to detect reliably, it may be possible to introduce it in a manner that increases its concentration in the capillary tube. This method of injection […]
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 […]
The basic instrumentation for capillary electrophoresis is shown here and includes a power supply for applying the electric field, anode and cathode compartments containing reservoirs of the buffer solution, a sample vial […]
In capillary electrophoresis we inject the sample into a buffered solution retained within a capillary tube. When an electric field is applied across the capillary tube, the sample’s components migrate as the […]
When an electrical field is applied to a capillary filled with an aqueous buffer we expect the buffer’s ions to migrate in response to their electrophoretic mobility. Because the solvent, H2O, is […]
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 […]
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, […]
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 […]
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 […]
