Sieving matrix capillary electrophoresis with polymer

This is a CE analog of conventional zone gel electrophoresis for the separation of macromolecules based on size. The capillary is filled with a porous polymer gel, and molecular sieving occurs as the molecules move through the gel, that is, separation is based on both electrophoretic mobility and molecular size. Very high resolution is achieved. The trend is to fill the capillary with a liquid gel matrix (pumpable gel solutions, such as deriyatized celluloses dissolved in the run buffer). This allows replacement of the gel in the capillary to eliminate contamination problems from the sample matrix that occurs with fixed gels.. This technique is widely used for separation of nucleotides in deoxyribonucleic acid (DNA) sequencing (Chapter 25). 

Capillary zone electrophoresis is not only the simplest form of CE, but also the most commonly utilized. Discussion of this mode permits the presentation of a generic design for the instrumentation for CE. The addition of specialized reagents to the separation buffer readily allows the same instrumentation to be used with the other modes mentioned in the previous section addition of surfactants with MEKC, ampholines for CIEF and a sieving matrix (linear polymers, entangled matrices) for CGE. The discussion on CZE in the following subsections allows for analysis of some of the basic principles governing analyte separation by this technique. 

Higher oligosaccharides or polysaccharides possess unfavorable mass-to-charge ratios, preventing their effective resolution in open tubes. The separation of these carbohydrates is possible with capillary gel electrophoresis (CGE). The analytes are selectively retarded by a sieving network (gel or polymer matrix) due to differences in their sizes and structural conformations. 

Sodium Dodecyl Sulfate-Capillary Gel Electrophoresis (SDS-CGE). SDS-CGE is a capillary-based version of SDS-polyacrylamide gel electrophoresis (SDS-PAGE) in the slab gel format, with advantages of shorter analysis times, ease of automation, and online detection and quantitation [26, 27]. In SDS-CGE, replaceable sieving polymers, such as linear polyacrylamide, poly (ethylene oxide), dextran, or pullulan, are used to achieve reproducible separations. These polymers permit the replacement of a separation matrix for each sample, thereby eliminating cross-contamination between samples and improving reproducibility. Best results are often obtained using chemically or dynamically coated capillaries. 

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