Zone electrophoresis, advantage

Capillary electrophoresis (CE) has several unique advantages compared to HPLC, snch as higher efficiency dne to non-parabolic fronting, shorter analytical time, prodnction of no or much smaller amounts of organic solvents, and lower cost for capillary zone electrophoresis (CZE) and fused-silica capillary techniques. However, in CZE, the most popular separation mode for CE, the analytes are separated on the basis of differences in charge and molecular sizes, and therefore neutral compounds snch as carotenoids do not migrate and all co-elute with the electro-osmotic flow. 

One of the major advantages of CE as a separation technique is the wide variety of separation modes available. Analytes can be separated on the basis of charge, molecular size or shape, pi, or hydrophobicity. The same CE instrument can be used for zone electrophoresis, IEF, sieving separations, isotachophoresis, and chromatographic techniques such as MEKC and capillary electrokinetic chromatography. This section provides a brief description of each separation mode. Zone electrophoresis, IEF, and sieving are the primary modes used for protein separations, and these will be discussed in detail in the following sections. 

Capillary zone electrophoresis (CZE) is the most common electrophoretic separation technique due to its simplicity of operation and its flexibility. It is the standard mode for drug analysis, identification of impurities, and pharmacokinetic studies. Other separation modes, such as capillary isotachopho-resis (CITP), micellar electrokinetc chromatography (MEKC), capillary electrochromatography (CEC), capillary gel electrophoresis (CGE), capillary isoelectric focusing, and affinity capillary electrophoresis (ACE), have then-advantages in solving specific separation problems, since the separation mechanism of each mode is different. 

The newest alternative to HPLC is capillary zone electrophoresis (CZE). Perhaps the greatest advantage to CZE is the ultralow detection limits and the extremely small samples necessary... 

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. 

Capillary electrophoresis (CE) coupled to MS has the advantage of high resolution and soft ionization for biomolecules, which may be used to differentiate post-translational modifications and variants of intact proteins and oligonucleotides. Different modes of CE (capillary zone electrophoresis, capillary isoelectric focusing, capillary electrochromatography, micellar electrokinetic chromatography, nonaqueous capillary electrophoresis) to MS as well as online preconcentration techniques (transient capillary isotachophoresis, solid-phase extraction, membrane preconcentration) are used to compensate for the restricted detection sensitivity of the CE methodology [77, 78]. 

The review of two-dimensional methods starts with the description of the principle and the advantages and main problems of the technique. Under a second heading the apparatus will be described, and many theoretical points will be discussed along with the development of the instrument because in two-dimensional techniques the relation between theory and practice is far more intricate than in zone electrophoresis. After this critical survey of the apparatus, a description of the run according to two different working conditions will close the review. 

An important advantage of two-dimensional methods is the solitary migration of each fraction on its own path. In contrast with unidimensional or zone electrophoresis where each fraction migrates its own distance but over a common path, no contamination of fractions is possible (Fig. 40). If the substrate is sufficiently long and wide and a high intensity electrical field is applied, it becomes possible to separate fractions reasonably completely from each other. If the physical forces involved are deployed skillfully, the electrical field can be driven up so that rapid and wide separations are obtained. This point is especially important in star electrophoresis, whereas in collecting electrophoresis mastery of the physical forces provides an excellent continuous preparative tool. 

It is the main advantage of this rapid two-dimensional technique that it applies the important principle of a two-dimensional method to microsamples there is no mixing of fractions running simultaneously on the same migration path as in zone electrophoresis, but on the contrary, uncontaminated fractions are separated within very short time. For clinical research the method has a bright future because of the theoretical purity of the spot, which is not obtainable with zone electrophoresis. Good results have already been gained in work on animal serum (Dl). 

To reduce adsorption of cellulose powder (T2) Flodin introduced ethanol-treated cellulose as a supporting medium for zone electrophoresis columns (FI). The main advantage is low adsorption, so that the column can be eluted and used over and over again. In the large models up to 2 liters of serum are separated, while microcolumns are under development which should give excellent results for clinical work (PI, Tl). 

In conclusion, capillary electrophoresis in carbohydrate analysis has advantages in both separation and detection over other techniques of electrophoresis, as well as chromatography. It allows high efficiency (up to a few million plate numbers) and very good sensitivities (up to femtomolar). In addition, CE permits analysis by a variety of separation modes simply by changing the electrolyte (capillary zone electrophoresis, MEKC, CGE). 

Various papers related to the simultaneous determination of creatinine and uric acid can be found in the hterature. Several authors have developed capillary zone electrophoresis (CZE) methods for simultaneous analysis of these compounds in urine. The CE analysis of these renal markers offers some advantages when compared with chromatography, such as shortened separation time, reduced reagent consumption, and increased resolution. Capillar micellar electrokinetic chromatography has been applied to the simultaneous separation of creatinine and uric acid in human plasma and urine. However, chromatographic techniques are widely accepted for the determination of these compounds. Reversed-phase and ion... 

The preceding examples elegantly demonstrate the point at which zone electrophoresis may be used to advantage in structural determinations on polysaccharides, namely, in further resolving fractions isolated by carbon-Celite column chromatography or paper chromatography, or both. 

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