Capillary electrophoretic techniques

The chloride ion is one of the most frequently analysed by IC, e.g. following up combustion of polymers [854,855] similar analyses were reported for the bromide ion [854,855] and nitrite [855]. Analysis of polyester resins for halogens or phosphorous components may be carried out via conversion to halides and phosphates, respectively. 

di- and tributyltin ion species (in water) have been determined by cation exchange IC-ICP-MS at 0.2 ng detection limits [856]. IC is also particularly useful for HSE purposes, such as the determination of acid gases in the workplace. Applications of IC have been reviewed [857]. 

Principles and Characteristics In electrophoresis the separation of electrically charged particles or molecules in a conductive liquid medium, usually aqueous, is achieved under the influence of a high electric field. This differs from chromatographic separations 

Capillary electrophoresis offers several useful methods for (i) fast, highly efficient separations of ionic species (ii) fast separations of macromolecules (biopolymers) and (iii) development of small volume separations-based sensors. The very low-solvent flow (l-10nL min-1) CE technique, which is capable of providing exceptional separation efficiencies, places great demands on injection, detection and the other processes involved. The total volume of the capillaries typically used in CE is a few microlitres. CE instrumentation must deliver nL volumes reproducibly every time. The peak width of an analyte obtained from an electropherogram depends not only on the bandwidth of the analyte in the capillary but also on the migration rate of the analyte. 

There are three main electrophoretic methods of separation (i) zone electrophoresis, where the components are separated on a basis of relative mobilities (ii) isotachophoresis, where the separation is again based on relative mobilities but where the solutes are sandwiched between leading and terminating electrolytes  

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The flow profiles of electrodriven and pressure driven separations are illustrated in Figure 9.2. Electroosmotic flow, since it originates near the capillary walls, is characterized by a flat flow profile. A laminar profile is observed in pressure-driven systems. In pressure-driven flow systems, the highest velocities are reached in the center of the flow channels, while the lowest velocities are attained near the column walls. Since a zone of analyte-distributing events across the flow conduit has different velocities across a laminar profile, band broadening results as the analyte zone is transferred through the conduit. The flat electroosmotic flow profile created in electrodriven separations is a principal advantage of capillary electrophoretic techniques and results in extremely efficient separations. 

Electrodriven separation techniques are destined to be included in many future multidimensional systems, as CE is increasingly accepted in the analytical laboratory. The combination of LC and CE should become easier as vendors work towards providing enhanced microscale pumps, injectors, and detectors (18). Detection is often a problem in capillary techniques due to the short path length that is inherent in the capillary. The work by Jorgenson s group mainly involved fluorescence detection to overcome this limit in the sensitivity of detection, although UV-VIS would be less restrictive in the types of analytes detected. Increasingly sensitive detectors of many types will make the use of all kinds of capillary electrophoretic techniques more popular. 

Deyl Z, Tagliaro F, MikSik I (1994a) Capillary electrophoretic techniques A new tool in clinical chemistry. Eur J Lab med 1 161-171. 

Terabe, S., Markuszewski, M.J., Inoue, N., Otsuka, K., Nishioka, T. Capillary electrophoretic techniques toward the metabolome analysis. Pure Appl. Chem. 73, 1563-1572 (2001)... 

Terabe, S., K. Otsuka, and H. Nishi, Separation of enantiomers by capillary electrophoretic techniques, /. Chromatogr. A 666 295 (1994). 

F. Foret, L. Kivdnkovd, and P. Boek, Principles of capillary electrophoretic techniques Micellar electroki- 8. netic chromatography, in Capillary Zone Electrophoresis (B. J. Radola, ed.), VCH, Weinheim, 1993, 9. 

Similarities and differences in chiral separation by chromatographic and capillary electrophoretic techniques... 

CM Boone, JP Franke, RA de Zeeuw, K Ensing. Evaluation of capillary electrophoretic techniques towards systematic toxicological analysis. J Chromatogr A 838 259-272, 1999. 

Nishi, H. and Terabe, S., Optical resolution of drugs by capillary electrophoretic techniques, J. Chromatogr. A, 694, 276, 1994. 

Capillary isoelectric focusing (CIEF) is designed to separate solutes based on their p/, the pH where they are electrically neutral. Because solutes do not migrate when they are neutral, the mobilization step distinguishes CIEF from other capillary electrophoretic techniques. This entry reviews the basis for CIEF including pH gradient formation, mobilization techniques, additives, and applications. 

Foret, F. Kivankova, L. Boek, P. Principles of capillary electrophoretic techniques Micellar electrokinetic chromatography. In Capillary Zone Electrophoresis, Radola, B.J., Ed. VCH Weinheim, 1993 67-74. 

Boone, C.M. Franke, J.-P. de Zeeuw, R.A. Ensing, K. Evaluation of capillary electrophoretic techniques towards 22. 

Chankvetadze B. Enantioseparations by using capillary electrophoretic techniques. The story of 20 and a few more years. J Chromatogr A 2007 1168 45—70. 

CAPILLARY ELECTROPHORESIS (CE) is a relatively new separation technology which combines aspects of both gel electrophoresis and high-performance liquid chromatography (HPLC). Like gel electrophoresis, the separation depends upon differential migration in an electrical field. Since its first description in the late 1960s, capillary electrophoretic techniques analogous to most... 

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