Capillary Electrochromatography CEC

During the course of time, many modifications have been reported in CEC and the technique is becoming popular. Gong and Lee [38] used 

CEC has also been used for the chiral analysis of pollutants, using a variety of chiral mobile phase additives. Cyclodextrin chiral selectors have been used for the chiral resolution of ibuprofen [49], 2-phenylpropionic acid and warfarin [50]. Other chiral selectors that have been resolved include warfarin on human semm albumin [51], ibuprofen on avidin [52], dichloroprop, ibuprofen, warfarin and thalidomide on vancomycin [53], ibuprofen and warfarin on teicoplanin [54], thalidomide and warfarin on 

Electrochromatography was first demonstrated in the open-tubular microfluidic channel coated with octadecylsilane (ODS) as the chromatographic stationary phase. EOF was used as the pumping system within the 5.6-pm-deep and 66-pm-wide channels. Plate heights of 5.0—44.8 pm were achieved for three cou-marin dyes [112]. Open-channel CEC separation was achieved using a stationary phase of octadecyltrimethoxysilane [148], CEC separation of some PAHs has also been carried out on a Pyrex chip with a thin film of C8 stationary phase formed using a sol-gel process [338], 

FIGURE 6.19 Fluorescence CCD images of tITP-ZE separation during injection (b) and after IIP concentration (c). (a) shows the general microfluidic channel configuration. Panels (b) and (c) show results obtained with a 250-pm injector. Conditions Sample was 1 mM fluorescein. Leading electrolyte 25 mM Tris+, 25 mM Cl. Trailing electrolyte 25 mM Tris+, 25 mM TAPS. Injection field 300 V/cm, current 18 pA. Separation field 200 V/cm, current 10 tl.A [634]. Reprinted with permission from the American Chemical Society. 

FIGURE 6.20 Experimental electropherograms of fluorescein under floating (float) and pinch-and-pufl-back (p+pb) conditions with (a) no NaCl and (b) 25 mM NaCl added to the sample [635]. Reprinted with permission from The Royal Society of Chemistry. 

FIGURE 6.21 Comparison of resolution and detection sensitivity of ITPZE and ZE separations. Sample, dsDNA ( )X I lAHlae in 0.1 x PCR buffer. The ZE sample has a 25x higher total DNA concentration than the ITPZE sample. The average signal enhancement from ITP is 40-fold [636]. Reprinted with permission from Wiley-VCH Verlag. 

In CEC, there is an additional factor in band broadening due to mass transfer, Hm. The Van Deemter equation is given in Equation (6.10) [112]  

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Capillary Electrochromatography Another approach to separating neutral species is capillary electrochromatography (CEC). In this technique the capillary tubing is packed with 1.5-3-pm silica particles coated with a bonded, nonpolar stationary phase. Neutral species separate based on their ability to partition between the stationary phase and the buffer solution (which, due to electroosmotic flow, is the mobile phase). Separations are similar to the analogous HPLC separation, but without the need for high-pressure pumps, furthermore, efficiency in CEC is better than in HPLC, with shorter analysis times. 

CE was recently used for anthocyanin analysis because of its excellent resolution. This technique has different modes capillary zone electrophoresis (CZE), capillary gel electrophoresis (CGE), micellar electrokinetic chromatography (MEKC), capillary electrochromatography (CEC), capillary isoelectric focusing (CIEE), and capillary isotachophoresis (CITP)."° CZE is the most popular method for anthocyanin... 

LC is currently used extensively in the photographic industry. One application is to quantify some of the components of photographic paper. As demands to reduce analysis time increase, an analytical method that can give improved productivity is required. One possible alternative to LC is capillary electrochromatography (CEC). In a recent paper, this analytical protocol was applied to separate some color photographic paper components <2002MI1>. 

This overview concerns the new chromatographic method - capillary electrochromatography (CEC) - that is recently receiving remarkable attention. The principles of this method based on a combination of electroosmotic flow and analyte-stationary phase interactions, CEC instrumentation, capillary column technology, separation conditions, and examples of a variety of applications are discussed in detail. 

CE is a family of techniques similar to those found in conventional electrophoresis zone electrophoresis, displacement electrophoresis, isoelectric focusing (IEF), and sieving separations. Other modes of operation unique to CE include micellar electrokinetic chromatography (MEKC) and capillary electrochromatography (CEC). 

This review provides an overview of the literature published to date on macrocyclic antibiotics exploited for enantioselective separations in high-performance liquid chromatography (HPLC). It was not intended as a comprehensive issue on the applications of such antibiotics in sub- and supercritical fluid chromatography (SFC), thin layer chromatography (TLC), capillary electrophoresis (CE), and capillary electrochromatography (CEC). A number of structural properties of the most important macrocyclic antibiotics applied in HPLC enantioseparations are listed in Table 2.1. 

Capillary electrochromatography (CEC) is a miniaturized separation technique that combines aspects of both interactive chromatography and capillary electrophoresis. In this chapter, the theory of CEC and the factors affecting separation such as the stationary phase and mobile phase parameters have been discussed. The chapter focuses on the types and preparation of columns for CEC and describes the progress made in the development of open-tubular, particle-packed, and monolithic columns. The detection techniques in CEC such as the traditional UV detection and improvements made in coupling with more sensitive detectors such as mass spectrometry are also described. The chapter provides a summary of some applications of CEC in the analysis of pharmaceuticals and biotechnology products. 

Dedicated applications of capillary zone electrophoresis (CZE) coupled to MS are discussed, particularly in the field of drug analysis. Development of other capillary-based electrodriven separation techniques such as non-aqueous capillary electrophoresis (NACE), micellar electrokinetic chromatography (MEKC), and capillary electrochromatography (CEC) hyphenated with MS are also treated. The successful coupling of these electromigration schemes with MS detection provides an efficient and sensitive analytical tool for the separation, quantitation, and identification of numerous pharmaceutical, biological, therapeutic, and environmental compounds. 

CGE) and capillary electrochromatography (CEC) are also not covered. The authors took care to include all relevant references. Nevertheless, some noteworthy investigations may have been overlooked. Readers more interested in this specific field of ACE are therefore referred to recent reviews (1-7) that deal especially with different aspects of drug-protein binding interactions. 

Finally, when RPC methods are used in preparative studies with peptides, the opportunity routinely exists for subsequent analysis of the recovered fractions by a variety of analytical methods including high-speed RP-HPLC, HP-IEX, HP-HILIC, or HP-IMAC, zonal or micellar electrokinetic high-performance capillary electrophoresis (HP-CZE and MECK-CZE), capillary electrochromatography (CEC), or capillary isotachophoresis. The combination of the RPC information, drawn from the In k versus i > plots, with the data derived from on-line spectroscopic detection thus readily provides a comprehensive opportunity to assess the purity of an isolated peptide, many of the physicochemical features of the interaction, as well as a means to optimize the resolution in the RPC separation. 

Capillary electrochromatography (CEC) is a rapidly emerging analytical separation technique, with several different instrumental formats and prepacked CEC capillary columns now available. P15-323 As an advanced nanoseparation technology, CEC represents an orthogonal hybrid of HPLC and HP-CZE. As a consequence, resolution can be achieved... 

Figure 24 Schematic Illustration of the Migration Order of Positively Charged, Negatively Charged, and Uncharged (Neutral) Peptides Separated by Capillary Electrochromatography (CEC) with H,0/0rganic Mobile Phases and Sorbents of Appropriate EOF Properties...

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