Packed Column Electrochromatography

Capillary Electrochromatography. Capillary electrochromatography (CEC) is a hybrid technique that works on the basic principles of capillary electrophoresis and chromatography [41], This mode of chromatography is used on either packed or tubular capillaries/columns. The packed column approach was introduced by Pretorius et al. [60] in 1974, while open tubular CEC was presented by Tsuda et al. [61] a decade later. In 1984 Terabe et al. [62] introduced another modification in liquid chromatography, micellar electrokinetic capillary... 

The most obvious advantage of an electroosmotic pumping system is the flow profile. Electrochromatography has the same pluglike profile that is characteristic of all other modes of CE. Although the pluglike flow is less perfect in packed columns than in open tubes, it is still more uniform than the laminar flow profile of a pressure-driven system. Consequently, the same capillary would be expected to provide higher efficiencies when used in CEC than when used in pressure-driven systems.31 35,36... 

Separation of triglycerides is amenable to capillary electrochromatography using a 3 pm Hypersil ODS-packed column with acetonitrile-isopropanol-w-hexane (57 38 5 v/v/v) as mobile phase. With a 20- or 40 cm x 100 pm i.d. column the result seen in Fig. 10.13 can be obtained at 30 kV and 20°C [52]. The retention parameters were quite acceptable, as demonstrated by RSD of the individual analytes present. The same approach is recommendable for analysing a formulation consisting of some... 

In a study presented by Jinno et al. [124], packed column capillary electrochromatography, open-tubular CEC, and microcolumn liquid chromatography using a cholesteryl silica bonded phase have been studied to compare the retention behavior for benzodiazepines. The results indicated that CEC was a promising method, as it yielded better resolution and faster analysis than microcolumn LC for benzodiazepines. Similar selectivity to HPLC was noted, except for a few solutes that were charged under the separation conditions. Columns packed with the ODS and cholesteryl phases were compared and showed totally different migration orders of the analytes. The retention on the cholesteryl silica sta-... 

Colon LA, Guo Y, and Fermier A. Fritless packed columns for capillary electrochromatography Separation of uncharged compounds on hydrophobic hydrogels. Anal. Chem. 1996 68 2153-2151. 

AM Fermier, LA Colon. Capillary electrochromatography in columns packed by centripetal forces. J Microcol Sep 10 439-447, 1998. 

LC uses mostly packed columns, as the use of open tubular columns in this method is not practical because of the extremely small column diameters required for good separation. In gas chromatography, both packed and open tubular columns can be used, but the latter are far more popular because of their vastly superior properties. The mobile phase is usually forced through the stationary phase at elevated pressure, although other approaches are also possible (e.g., electrically driven flow in electrochromatography (EC), gravity driven flow in classical LC or flow driven by capillary forces in TLC). 

At present it seems that immobilization of silica-based particles within a packed capillary by hydrothermal treatment or sol-gel adhesion represent a simpler approach to the preparation of silica-based monoliths for capillary electrochromatography [302,332-334]. Particle fixation is achieved through adhesion by silica precipitated in the interparticle space released from the particles by hydrothermal treatment, or formed by hydrolysis and polycondensation of a solution of alkoxysilanes (sol-gel process). Since only relatively low temperatures are used in both processes, chemically bonded phases can be immobilized as easily as silica. The selectivity and separation efficiency of immobilized particle beds is generally similar to that of slurry packed columns prepared from the same stationary phases. 

Higher pressures are required for pressure-assisted separations in packed columns used for capillary electrochromatography [235,376,464-466]. These columns require a high-pressure pump to provide the supplementary mobile phase flow. Conventional rotary injection valves and autosamplers can be used for sample introduction with this arrangement if a special inlet tee housing the electrode and split line with a restrictor is installed [422]. Microcolumn pumps are also useful for conditioning columns before initial use in capillary electrochromatography (section 8.4.2). There are no com-... 

Electrochromatography is a hybrid of HPLC and Cli that offers some of the best features of the two methods. Like FIPI.C and MLKC. it is applicable to the separation of neutral species or charged species. Electrochromatography with packed columns is, however, the least mature of the various clectroscparaiion lech niques. In this method, a polar solvent is usually driven by eleclroosmotic flow through a capillary packed with... 

Yan, C., Schaufelberger, D., and Erni, R, Electrochromatography and micro high-performance liquid chromatography with 320 jjim I.D. packed columns, J. Chromatogr. A, 670, 15, 1994. 

Dermaux, A., et al.. Elucidation of the triglycerides in fish oil by packed-column supercritical fluid chromatography fractionation followed by capillary electrochromatography and electrospray mass... 

CEC in open-tubular and packed columns (Tsuda T (1987) Electrochromatography using high applied voltage. Analytical... 

Capillary electrochromatography packed capillary column HPLC in which the mobile phase moves as the result of an external electric field (electro-osmotic flow) rather than by external pressure. Very small particle sizes can be used since there is no back pressure problem. 

An entirely different concept in analytical separations is provided by capillary electrophoresis (CE) in which the flow of liquid is generated by electro-osmotic flow (EOF) driven by an external electric field. The major advantage of this approach is the essentiaUy flat plug flow profile that leads to intrinsically more narrow elution peaks than the parabolic flow profiles characteristic of pressure-driven viscous flows. In capillary zone electrophoresis (CZE) separation is achieved by superimposing the different electrophoretic mobihties of the solutes on to the EOF. In electrochromatography the separation is achieved as in packed column HPLC but using an EOF to generate flow of the mobile phase past the stationary phase particles. The importance of these EOF-based techniques is their application to miniaturized devices, lah-on-a-chip or micro total analysis systems. Such devices that can be directly interfaced to a mass spectrometer via an ESI source are currently under intense development. 

C. Fujimoto, Enantiomer separation by capillary electrochromatography using frittless packed columns. Anal. Sci., 2002, 18, 19-25. 

A An Overview of Electrophoresis 867 30B Capillary Electrophoresis 868 30C Applications of CE 875 30D Packed Column Electrochromatography 30E Field-Flow Fractionation 884 Questions and Problems 888... 

A new analytical method, pressurized capillary electrochromatography (pCEC) with AD using 1.5 mm reversed phase nonporous silica packed columns has been developed for the rapid separation and determination of four Sudan dyes in hot chili [36]. The influence of several experimental parameters on the retention behavior has been investigated. The electrochemical oxidation of Sudans I-FV separated by pCEC can be reliably monitored with a carbon electrode at 0.95 V (vs. Ag/AgCl). Fast and efficient separation of the analytes was achieved within 7 min by pCEC under the optimum conditions. To evaluate the feasibility and reliability of this method, the proposed pCEC-AD method was further demonstrated with hot chili samples spiked with Sudan dyes. 

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