Compared to electrophoresis

The theoretical basis of the transport of solute ions during iontophoresis can be compared to electrophoresis through a gel network. When the ionized solute has a mean Stokes radius smaller than the average mesh size (hole in the network), the solute is considered as a rigid sphere undergoing Brownian movement, with a mobility dependent on the frequency of solute interaction with the porous network. The sphere mobility is assumed to be proportional to the fractional volume of the pore that is accessible to the sphere [92]. The electrophoretic mobility, u, of such a solute sphere has been shown to be directly related to the molecular weight of the solute [93] ... 

For low Du the second term dominates its sign is opposite to that of Vc, whatever the sign of f. However, for other combinations of and Du reversal of direction may occur. Equation [4.9.3] may also be used to assess how strong the phenomenon of diffusiophoresls is, as compared to electrophoresis. To compare orders of magnitudes, let us assume that the second term dominates emd that Du = 1. The equation then reduces to... 

The use of standards with samples makes zone electrophoresis particulady usehil as an analytical tool. However, when samples caimot be analyzed on the same gel, differences in the experimental conditions from experiment to experiment make direct comparison more difficult. To make comparisons from experiment to experiment, a relative mobility, is often measured by measuring the distance a component travels down the gel compared to some reference or standard component. 

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. 

Comparisons of CE and HPLC on similar analytical problems have been reported [879-883]. In contrast to CE and HPLC, GC is best suited for analysis of nonpolar, lower MW, volatile compounds. HPLC and GC have detection limits roughly 100-1000 times lower than CE, while traditional electrophoresis has detection limits comparable to CE. As already mentioned, the inferior detection sensitivity and precision of CE when compared with HPLC are caused by the technique s nanoscale. 

Because HPLC and HPCE are based on different physico-chemical principles, HPCE may be expected to address areas in which HPLC has shortcomings [884]. One such area is time of separation. In terms of speed of analysis, selectivity, quantitation, methods to control separation mechanism, orthogonality, CE performs better than conventional electrophoresis and varies from HPLC (Table 4.49). CE has very high efficiency compared to HPLC (up to two orders of magnitude) or GC. For typical capillary dimensions 105—106 theoretical plates are common in CE compared to 20 000 for a conventional HPLC column and... 

The total proteins synthesized by bacteria grown under standard conditions, when analyzed by polyacrylamide gel electrophoresis (PAGE), form patterns that can be compared to those of known strains by visual or computer-assisted... 

The use of electrically-gated solute injection into the electrophoresis system simplifies the chip design as electrical connections are easy to implement as compared to the microfluidics part of the chip. Voltage waveform manipulation via hardware and software are relatively easy to control and implement. 

Influence of the Surface Concentration of BSA. Compared to the corrected moving boundary electrophoretic mobility of BSA in solution, the mobility of BSA adsorbed onto glass is considerably faster at all ionic strengths at 1.96 pg/cm2 and somewhat faster at lower ionic strengths 1.38 pg/cm2. However, at lower adsorption densities (1.05 and 0.64 pg/cm2), the adsorbed BSA moves more slowly in the applied electric field than BSA in moving boundary electrophoresis under otherwise identical conditions, and at the lowest surface adsorption (0.64 pg/cm2) the mobility of the adsorbed BSA are even somewhat slower than in cellulose acetate gel at all conditions of ionic strength investigated. 

In the last decade, capillary electrophoresis (CE) has become one of the most powerful and conceptually simple separation techniques for the analysis of complex mixtures. The main reasons are its high resolution, relatively short analysis times, and low operational cost when compared to high-performance liquid chromatography (HPLC). The ability to analyze ultrasmall volume samples in the picoliter-to-nanoliter ranges makes it an ideal analytical method for extremely volume-limited biological microenvironments. 

Over the last two decades mass spectrometry has become one of the central techniques in analytical chemistry, and the analysis of biological (macro)molecules in particular. Its importance is now comparable to that of the more traditional electrophoresis and liquid separations techniques, and it is often used in conjunction with them as so-called hyphenated techniques, such as LC-MS. 

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