Capillary electrophoresis power supply

The basic instrumentation for capillary electrophoresis is shown in Figure 12.41 and includes a power supply for applying the electric field, anode and cathode compartments containing reservoirs of the buffer solution, a sample vial containing the sample, the capillary tube, and a detector. Each part of the instrument receives further consideration in this section. 

A schematic representation of a CE system is presented in Figure 9.1. In this diagram, the CE components have obvious counterparts to those found in slab gel electrophoresis. Instead of buffer tanks there are two small buffer reservoirs, and the capillary takes the place of the gel (or more accurately, a gel lane). The capillary is immersed in the electrolyte-filled reservoirs, which also make contact with the electrodes connected to a high-voltage power supply. A new feature to the conventional gel electrophoresis format is the presence of an online detection system. 

Figure 9.1 Schematic representation of a basic capillary electrophoresis system. The main components include a capillary (commonly contained within a housing that allows for temperature control), a power supply, and a detector. Automation is achieved through the use of computer-controlled setting of solutions and samples, displacement forces (to replace capillary contents and for hydrodynamic injection), and automatic data collection. (Courtesy of Agilent Technologies.)...

Capillary electrophoresis (CE) instrument is quite simple. A CE, at its core, is merely a high-voltage power supply (capable of voltages in excess of 30,000 V), capillary (approximately 25 to 100 pm inner diameter), buffers to complete the circuit (e.g., citrate, phosphate, acetate, etc.), and a detector (e.g., UV-Vis). There are additional complexities, of course, but at its heart, the CE is a simple instrument. 

Capillary Zone Electrophoresis. The primary advantage of capillary electrophoresis can be found in the simplicity of the instrument. Basic experimental components include a high-voltage power supply, two buffer reservoirs, a fused silica capillary, and a detector. The basic setup is usually completed with enhanced features such as multiple injection devices, autosamplers, sample and capillary temperature controls, programmable power supplies, multiple detectors, fraction collection, and computer interfacing. 

Jackson, D.J., Naber, J.F., Roussel, T.J., Jr., Crain, M.M., Walsh, K.M., Keynton, R.S., Baldwin, R.P., Portable high-voltage power supply and electrochemical detection circuits for microchip capillary electrophoresis. Anal. Chem. 2003, 75, 3643-3649. 

A capillary electrophoresis system is comparatively simple. The basic components (Fig. 6.1) include the power supply which provides the high voltage necessary for the separation, the capillary in which the separation takes place, the detector which determines the sensitivity of the separation, and the data acquisition system which records the electropherogram. Some instruments also perform fraction collection. The final electropherogram looks similar to a chromatogram obtained from HPLC. 

Electrophoresis — Movement of charged particles (e.g., ions, colloidal particles, dispersions of suspended solid particles, emulsions of suspended immiscible liquid droplets) in an electric field. The speed depends on the size of the particle, as well as the -> viscosity, -> dielectric permittivity, and the -> ionic strength of the solution, and it is directly proportional to the applied electric field. In analytical as well as in synthetic chemistry electrophoresis has been employed to separate species based on different speeds attained in an experimental setup. In a typical setup the sample is put onto a mobile phase (dilute electrolyte solution) filled, e.g., into a capillary or soaked into a paper strip. At the ends of the strip connectors to an electrical power supply (providing voltages up to several hundred volts) are placed. Depending on their polarity and mobility the charged particles move to one of the electrodes, according to the attained speed they are sorted and separated. (See also - Tiselius, - electrophoretic effect, - zetapotential). 

Figure 4-33. Block diagram of capillary electro- carried out close to the cathode in a region phoresis equipment. Capillary electrophoresis where the capillary is transparent, allowing equipment consists of a thermostatted capillary photometric or fluorimetric analysis of the whose ends are placed in the electrode buffer eluate. The detector system is linked either to a chambers these contain the electrodes attached recorder/integrator or to a PC. to a high-voltage power supply. Detection is...

The basic apparatus necessary for a capillary electrophoresis system is shown in Fig. 2. The instrument must have the following components power supply, electrodes (anode and cathode), vials for electrodes and buffers, separation capillary, detector, and data... 

The instrumental arrangement commonly employed in capillary electrophoresis is shown in Figure 12.1. With untreated silica capillaries, electroosmosis causes the buffer to flow from the anode to the cathode. Samples are introduced at the anodic end, and an on-column or post-column detector is placed at or near the cathodic end of the capillary. The high-voltage produced by the power supply and present in the anodic buffer reservoir is enclosed in a protective shield. 

The power supply drives the movement of ionic species in the medium and allows adjustment and control of either the current or the voltage. In more sophisticated units, the power may be controlled as well and conditions may be programmed to change during electrophoresis. Capillary systems use power suppfies capable of providing voltages in the kilovolt range. 

Figure 10.1. Schematic representation of a capillary electrophoresis instrument. A, electrolyte reservoirs B, platinum electrodes C, fused silica capillary D, detector cell E, high-voltage power supply.

Capillary electrophoresis instrumentation includes a power supply, injector, capillary and detector. It is often set up as a modular system where the power supply, detector and other modules are bought separately off the shelf and configured by the scientist. The heart of the system is the capillary where separation occurs. Because capillaries in CE are mostly open tubular and not packed, resolution is excellent and peaks are very sharp. A high voltage is required to move the buffer through the capillary. 

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