Capillary electrophoresis apparatus

H. Yamamoto, T. Manabe and T. Okuyama, Apparatus for coupled high-performance liquid chromatography and capillary electrophoresis in the analysis of complex protein mixtures , 7. Chromatogr. 515 659-666 (1990). 

Figure 9 Schematic diagram for capillary electrophoresis with postcapillary ECL detection. (A) Overview of the apparatus. (B) Enlarged view of the etched joint and ECL detection cell. The PMT (not shown) is positioned directly over the Pt working electrode, and the entire apparatus placed inside a light-tight housing. (From Ref. 64.)...

Capillary procedures offer several advantages, including speed, resolution, sensitivity and technical simplicity, compared with the traditional methods on which they were based. An added advantage for iso-electric focusing in capillaries is the fact that it can be performed without a gel, but a coating on the internal surface of the capillary is usually required to reduce electroendosmosis. Similarly, isotachophoresis can be conveniently performed in capillary electrophoresis apparatus. 

Figure 26-17 Apparatus for capillary electrophoresis. One way to inject sample is to place the capillary in a sample vial and apply pressure to the vial or suction at the outlet of the capillary. The use of an electric field for sample injection is described in the text. 

Finally, equipment for assaying and analyzing the preparations is needed. Most such equipment is fairly standard in biochemical laboratories and includes spectrophotometers, scintillation counters, analytical gel and capillary electrophoresis apparatuses, immunoblot-ting materials, and immunochemical reagents. 

Figure 2. A Schematic Diagram of an Automatic Modular Capillary Electrophoresis Apparatus with On-column Detection. (Reproduced with permission from Ref. 71. Copyright 1988 Academic Press.)...

These features allow good separation and identification of these nucleotides. Capillary electrophoresis showed excellent linearity between 0 and 40 mM concentration. Considering that in the present conditions the capillary electrophoresis apparatus can load approximately 4 nl, we estimate that the assay is linear between 0 and 160 picomoles. The fact that the zone containing a particular nucleotide is not deformed after successive runs permits rapid spectral analysis in a mixture of nucleotides by reversing the field polarity. This is particular important for unstable nucleotides such as c-IMP. 

Most types of electrophoresis using supporting media are simple to carry out and the apparatus can be easily constructed, although inexpensive equipment is commercially available. High-resolution techniques such as two-dimensional electrophoresis and capillary electrophoresis require more sophisticated equipment, both for separation and analysis (see later). 

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 increase in temperature during a separation is observed to be due to Joule heating Ideally, the retention factor, k, should be independent of the applied voltage or current, but, actually, k does depend on the applied voltage. Although the temperature of the separation capillary is controlled with a Uquid coolant or a drculating airstream in most commercially available capillary electrophoresis (CE) instruments, the retention factor usually deaeases, almost linearly, with an increase in the velocity of the EOF or an increase in the current. However, the dependence is much less than that observed in a CE system without forced-cooling apparatus. 

Fig. 6.8. Cross-sectional view of apparatus for electrophoresis in fused salts, (a) Electrophoresis chamber (b) Pyrex glass plate (c) Pyrex vessels (d) glass fibre paper (e) capillary with a screw to move it in all directions (0. furnace with heating and temperature regulating system g.i., gas inlet tube g.o., gas outlet tube.

The instrumentation required for Capillary Electrophoresis is relatively simple. A typical example of a CE apparatus is shown in Fig. 3.12, consisting of vials... 

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