Electrochromatography, micellar capillary

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... 

Capillary electrophoresis (CE) coupled to MS has the advantage of high resolution and soft ionization for biomolecules, which may be used to differentiate post-translational modifications and variants of intact proteins and oligonucleotides. Different modes of CE (capillary zone electrophoresis, capillary isoelectric focusing, capillary electrochromatography, micellar electrokinetic chromatography, nonaqueous capillary electrophoresis) to MS as well as online preconcentration techniques (transient capillary isotachophoresis, solid-phase extraction, membrane preconcentration) are used to compensate for the restricted detection sensitivity of the CE methodology [77, 78]. 

Figure 4.2 Classification of electrophoresis according to the contribution of the electroosmotic flow. CZE, Capillary zone electrophoresis MECC, micellar electrokinetic capillary chromatography CEC, capillary electrochromatography cIEF capillary isoelectric focusing cGE, capillary gel electrophoresis.

Since a chromatographic mechanism (solute partitioning between two phases moving relative to one another) is involved in micellar capillary electrochromatography, the theory outlined above for band broadening in electrophoresis does not apply. Theoretical aspects of MCE have been developed by Terabe et al. [36] and by Davis [37]. 

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). 

After a short introduction into the relevance of Impurity profiling for regulatory authorities, public health, and the pharmaceutical industry, an overview is presented based on the various modes of capillary electrophoresis that have been used in drug impurity analysis. The applications of capillary zone electrophoresis, non-aqueous capillary electrophoresis, micellar electrokinetic capillary chromatography, microemulsion electrokinetic capillary chromatography, capillary gel electrophoresis, and capillary electrochromatography are presented consecutively. 

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. 

Giordano, B. C., C. L. Copper, and G. E. Collins. Micellar electrokinetic chromatography and capillary electrochromatography of nitroaromatic explosives in seawater. 

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. 

Micellar etectrokinetic chromatography electrophoresis with micelles acting as pseudostationary phase Capillary electrochromatography similar to HPLC, except mobile phase is driven by electroosmosis instead of pressure... 

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 first and most often encountered separation mechanism in CE is based on mobility differences of the analytes in an electric field these differences are dependent on the size and charge-to-mass ratio of the analyte ion. Analyte ions are separated into distinct zones when the mobility of one analyte differs sufficiently from the mobility of the next. This mechanism is exemplified by capillary zone electrophoresis (CZE) which is the simplest CE mode. A number of other recognized CE modes are variations of CZE. These are micellar electrokinetic capillary chromatography (MECC), capillary gel electrophoresis (CGE), capillary electrochromatography (CEC), and chiral CE. In MECC the separation is similar to CZE, but an additional mechanism is in effect that is based on differences in the partition coefficients of the solutes between the buffer and micelles present in the buffer. In CGE the additional mechanism is based on solute size, as the capillary is filled with a gel or a polymer network that inhibits the passage of larger molecules. In chiral CE the additional separation mechanism is based on chiral selectivity. Finally, in CEC the capillary is packed with a stationary phase that can retain solutes on basis of the same distribution equilibria found in chromatography. 

Capillary electrochromatography (CEC) is a rapidly emerging technique that adds a new dimension to current separation science. The major "news" in this method is that the hydrodynamic flow of the eluting liquid, which is typical of HPLC, is replaced by a flow driven by electro-endoosmosis. This increases considerably the selection of available separation mechanisms. For example, combinations of traditional processes such as reversed-phase- or ion-exchange- separations with electromigration techniques are now possible. Also, CEC is opening new horizons in the separation of non-polar compounds, and thus represents an alternative to the widely used micellar electrokinetic chromatography. 

The separation scientist with experience gained from a LC background may tend to limit the modes of electrochromatography to reversed phase (RP), normal phase, ion-exchange and, maybe, size-exclusion. Analysts from an electrophoretic background typically use the term "CE" in a much broader sense to include the main modes of capillary zone electrophoresis, micellar electrokinetic chromatography, capillary gel electrophoresis, isoelectric focusing and isotachophoresis. 

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