Continuous flow through electrophoresis

This procedure represents a preparative version of zone electrophoresis. The apparatus and technique has been previously elaborated [294,295] separation itself is carried out either in a stream of electrolytic solution or on a sheet of cardboard (curtain electrophoresis). In the free flow version the separation is carried out in a cell formed by two parallel glass plates (50 x 50 cm) situated 0.5-1.0 mm apart. It is necessary to ensure an equal and laminar flow of the electrolyte, which is carried out by feeding the buffer through a multichannel peristaltic pump. The sample is continuously applied in the middle near the upper edge of the cuvette (or paper sheet). The electrophoretic separation occurs transversally between vertical electrodes located on the right and left hand side of the separation cuvette (Fig. 6.33). The separated fractions are collected at the lower end of the cell by a system of small communicating vessels or by a multi-channel pump. In the version using paper the 

The version without support has, especially, the advantage of circumventing the problem of recovering the separated material from the supporting medium there- 

The apparatus of Hannig is most well known however apparatuses of cylindrical or disc shape, or exploiting the effects of the magnetic field, have also been described (for review see Ref. 296). 

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The apparatus for continuous flow-through electrophoresis with slight modification is used for this procedure (see page 487). It consists of two glass plates (e.g. 

In continuous-flow zone electrophoresis the solute mixture to be separated is injec ted continuously as a narrow source within a body of carrier fluid flowing between two electrodes. As the solute mixture passes through the transverse field, individual components migrate sideways to produce zones which can then be taken off separately downstream as purified fractions. 

Recycling effluent through a thin-film continuous flow electrophoresis (CFE) chamber allows virtually complete separation of a binary feed with negligible dilution of products and permits throughput to be increased by 0(100-10,000) over present thin-film CFE devices. An approximate model of recycle CFE is developed for the high Peclet number regime and solved analytically. The solution is used to characterize the behavior of a recycle CFE device. 

Fre- flow electrophoresis is the only continuous electrophoretic separation method. The electrical field is applied perpendicular to a continuous stream of buffer film, which flows through a 0.5-1.0 mm wide cuvette. At one end the sample is injected at a defined location, and at the other end, the fractions are collected by an array of tubes. The different electrophoretic mobilities of the sample components lead to differently strong but constant deviations inside the stream... 

A new and ingenious principle for preparative electrophoresis was published from the Tiselius laboratory, in 1949, by Svensson and Brattsten (72). They described a method for continuous electrophoretic separation in liquids flowing through a packed channel. The current was applied at right angles to the flowing liquid and the separated fractions were col-... 

Figure 7.3.4. Diagrammatic representation of the continuous-flow electrophoretic separator, (a) Cutaway drawing of the system showing the construction of the rotor, stator and main flow channels, (b) Separation of three components as they are carried up through the annulus. From Figure 2, p. 7 of "Velocity gradient stabilized continuous free flow electrophoresis. A review," P. Mattock, G.P. Aitchison, A.R. Thomson, Separ. Purif. Meth., 9(1), 1 (1980) reprinted by permission of the publisher (Taylor and Francis Group, http //www. informaworld.com).

In preparative continuous free flow electrophoresis, continuous buffer and sample feed are introduced at one end of a thin, rectangular electrophoresis chamber. A schematic is presented in Fig. 11-5. The sample stream is usually introduced through a single port while buffer is introduced through several ports, essentially producing a buffer curtain . Because the buffer streams are introduced independently, it is fairly easy to establish a variety of gradients (e.g., pH, density, ionic strength) across the buffer curtain . 

Electrophoresis can also be conducted on-line, as an element of industrial process monitoring and/or control. In this case a slip-stream sample is usually withdrawn from a process vessel, diluted in a mixing tank to reduce the sample turbidity, and then pumped through an electrophoresis cell that is fitted with stop-flow solenoid valves. The flow is stopped for long enough to make an electrophoresis measurement and then resumed. The sampling can be either intermittent or continuous. An example is described in reference [265]). 

A modification to electrophoresis is free-flow electrophoresis, which enables the continuous separation of a mixture according to charge with subsequent collection of the sample band of interest [244]. For this, an transverse electric field is applied in pressure driven flow within a broad and flat microchamber. While passing this extraction chamber, the species contained in the sample flow are deflected depending on their charge and thus exit the chamber through one of several outlets. 

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