CE system

The design and testing of these developmental plants are well underway. The evolutionary designs have received final design approval from the U.S. NRC. As of 1995 evolutionary ALWR designs very similar to these, by the same U.S. manufacturers, are already being built in Asia the GE-Advanced BWR in Japan and the ABB-CE System 80+ PWR in South Korea. The N-4 PWR is under constmction in Prance, and the SizeweU PWR has completed constmction and has initiated operation in the U.K. 

A novel interface to connect a ce system with an inductively coupled plasma mass spectrometric (icpms) detector has been developed (88). The interface was built using a direct injection nebulizer (din) system. The ce/din/icpms system was evaluated using samples containing selected alkah, alkaline earths, and heavy-metal ions, as well as selenium (Se(IV) and Se(VI)), and various inorganic and organic arsenic species. The preliminary results show that the system can be used to determine metal species at ppt to ppb level. 

The use of SPME for CE has not (yet) been studied widely. Li and Weber (170) reported an off-line SPME-CE approach for the determination of barbiturates in urine and serum, utilizing a sorbent of plasticized PVC coated around a stainless steel rod. Eor extraction, the coated rod was inserted for 4 min in a Teflon tube containing 50 p.1 of sample, and next the rod was repeatedly desorbed in another Teflon tube which each time contained 5 p.1 of desorption solution. This solution was transferred to an injection vial and an aliquot was injected into the CE system (Eigure 11.19). The extraction procedure appeared to be selective and effectively allowed the handling of very small samples. 

Analogous to two-dimensional LC, the on-line coupling of LC and CE has been carried out both in the heart-cut and the comprehensive mode. In a heart-cut LC-CE study, a protein G immunoaffinity LC column was used to selectively preconcentrate insulin from serum (171). A 1 p.1 elution plug comprising the insulin was switched on-line to the CE system where a part was injected into the capillary for final separation. With CE, efficient separations can be obtained in a... 

As in CE, changing system variables (e.g., pH, ionic strength, additive concentration) is very easy in any of the continuous free flow electrophoresis systems reported here because all the interactions take place in free solution. Indeed, changing system variables may be easier in continuous free flow electrophoresis systems than in a CE system because there are essentially no wall effects. Of course, changing system variables in the continuous free flow electrophoresis apparatus may also be easier... 

James and Hagee have reported a study of the high temperature vaporization chemistry in the Au-Ce system including the formation of vapour complex species of gold and silver with copper and iron. 

The Intermetallic Li-Zn-Ce System, from Electron-poor to Electron-rich Phases 149 9.5... 

Reactions of partial electrochemical oxidation are of considerable interest in the electrosynthesis of various organic compounds. Thus, at gold electrodes in acidic solutions, olefins can be oxidized to aldehydes, acids, oxides, and other compounds. A good deal of work was invested in the oxidation of aromatic compounds (benzene, anthracene, etc.) to the corresponding quinones. To this end, various mediating redox systems (e.g., the Ce /Ce system) are employed (see Section 13.6). 

Many instrumentation companies have commercialized complete or modular CE systems. The principal vendors are Beckman Instruments, Inc. (Fullerton, CA) Bio-Rad Laboratories (Hercules, CA) Dionex Co. (Sunnyvale, CA) Hewlett Packard (Palo Alto, CA) ISCO, Inc. (Lincoln, NE) Otsuka, Ltd. (Tokyo, Japan) Perkin-Elmer -ABI (Foster City, CA) Thermo-Separation Products (Fremont, CA) and Waters Associates (Milford, MA). 

Eqns. 3.71-3.74 show the possibility of checking the mechanism of the respective electrode reactions on the basis of their logarithmic term containing <1/2 and r1/2 in all the instances the product ir1 2 is constant as a function of the constant i chosen however, when a chemical reaction necessarily precedes the electron transfer reaction, i.e. in a CE system, it11 2 decreases with increasing i. 

FIGURE 5.10 The image of a microchip used in 2D MEKC-CE described in Ramsey et al. (2003). Note that injections are made at valve 1 (VI) for the first-dimension MEKC separation. Solute is sampled into the CE system at V2. Other designations are provided in the original reference. This figure is used by permission of the American Chemical Society. 

As yet, the number of applications is limited but is likely to grow as instrumentation, mostly based on existing CE systems, and columns are improved and the theory of CEC develops. Current examples include mixtures of polyaromatic hydrocarbons, peptides, proteins, DNA fragments, pharmaceuticals and dyes. Chiral separations are possible using chiral stationary phases or by the addition of cyclodextrins to the buffer (p. 179). In theory, the very high efficiencies attainable in CEC mean high peak capacities and therefore the possibility of separating complex mixtures of hundreds of... 

The first commercial CE instruments were introduced in 1988 by Applied Biosystems (Foster City, CA) and Beckman Coulter (Fullerton, CA). The main challenge during these days was to find out how to overcome poor reproducibility and improve separation efficiency. In the early 1990s, many instrument-building companies introduced CE systems (e.g. Isco (Lincoln, NE), Bio-Rad (Hercules, CA), Waters (Milford, MA), Applied Biosystems, ThermoQuest (Santa Fe, NM) and Dionex (Sunnyvale, CA)), but at the end of the decade only Beckman Coulter... 

Fig. 17.8. Representation of a CE system. (1) Electrolyte compartments, (2) the capillary, (3) detector, (4) power supply, (5) sample carousel, (6) electrodes, (7) thermostatted areas and (8) data workstation.

As was mentioned previously, photometric detection is the most frequently applied detection technique. Most of the commercial CE-systems are equipped with at least a UV detector. Some compounds, such as low molecular weight organic and inorganic ions [57-60], do not produce a direct analytical signal. In such cases indirect detection, by indirect UV or fluorescence [59-64] is applied. Besides photometric detection, an application of indirect amperometric [65] detection was also reported. When the analytical signal results from a decrease in... 

The application of an organic solvent in CE offers a new possibility to change the selectivity of CE systems. Moreover, the various ion-solvent interactions and ion-pair formations can be exploited for increased separation efficacy. Its application for CE analysis of ionic synthetic dyes may be expected in the future [121],... 

The effective mobility (/ieff) of the solute is the weighted average of the mobilities of all forms of solutes in the CE system ... 

The CE theories briefly discussed above can be applied to the prediction of the electrophoretic mobility of natural pigments and synthetic dyes too, and for the design of a CE system for their optimal separation. 

A schematic representation of a CE system is presented in Figure 9.1. In this diagram, the CE components have obvious counterparts to those found in slab gel electrophoresis. Instead of buffer tanks there are two small buffer reservoirs, and the capillary takes the place of the gel (or more accurately, a gel lane). The capillary is immersed in the electrolyte-filled reservoirs, which also make contact with the electrodes connected to a high-voltage power supply. A new feature to the conventional gel electrophoresis format is the presence of an online detection system. 

---