Capillary electrophoresis, free-flow

Kasicka, V., Pruslk, Z., Sazelova, P., Jiracek, J. and Barth, T., Theory of the correlation between capillary and free-flow zone electrophoresis and its use for the conversion of analytical capillary separations to continuous free-flow preparative processes. Application to analysis and preparation of fragments of insulin, ]. Chromatogr. A, 796, 211, 1998. 

A variety of methods has been applied to the separation of bound and free Ag. These include precipitation, solid phase attachment, capillary electrophoresis, chromatography, andmicrofiltration. Originally, precipitation and solid-phase extraction were the most common types of separations techniques. However the ease of automation of capillary electrophoresis and flow-injection analysis (chromatography) makes these two techniques very interesting. 

Currently, there are five major modes of operation of CE capillary zone electrophoresis (CZE), also referred to as free solution or free flow capillary electrophoresis micellar electrokinetic chromatography (MEKC) capillary gel electrophoresis (CGE) capillary isoelectric focusing (CIEF) and capillary isotachophoresis (CITP). Of these, the most commonly utilized capillary techniques are CZE and MEKC (Rabel and Stobaugh 1993 Issaq 1999 Smyth and McClean 1998). 

Schmitt-Kopplin, P., and Kettrup, A. (2003). Capillary electrophoresis-electrospray ionization-mass spectrometry for the characterization of natural organic matter An evaluation with free flow electrophoresis-off-line flow injection electrospray ionization mass spectrometry. Electrophoresis 24, 3057-3066. 

The key operational parameter in free-solution capillary electrophoresis is the pH of the running buffer, as the electroosmotic flow and ionization of the analyte can be regulated by this variable. The role of buffers in capillary electrophoresis has been discussed in detail, with emphasis on buffer concentration, buffer type, and pH effects [10]. The effect of organic solvents on separation and migration behavior has been studied for dipeptides [11] and somatostatin analog peptides [12]. The order of migration as well as the selectivity may be manipulated by organic modifiers in... 

To remove carrier ampholytes when electrospray ionisation mass spectrometry is used on-line with capillary isoelectric focusing, a specially designed free-flow electrophoresis device can be coupled to the CIEF system [67],... 

This technique has proven to be a powerful separation technique for the separation of macromolecules, such as antibodies, for two reasons the near flat plug flow profile and the small diffusion constant of the antibodies. These characteristics eliminate band broadening. With both superior separation power and high detection sensitivity, capillary electrophoresis (CE) can separate free Ab and Ag from bound Ab and Ag rapidly and is suitable for immunoassays. CE can combine immunologic recognition with on-line quantitation, microscale... 

Electrophoretic methods are widely used alternatives for the analytical determination of the enantiomeric purity of chiral compounds [194]. Due to the high elTi-ciency of capillary electrophoresis, separations can be achieved even when very low selectivities are observed. At a preparative scale, these methods are well established for the purification of proteins and cells [195] but there is very little published on enantioselective separations. Only recently, some interest in chiral preparative applications has been manifested. Separation of the enantiomers ofterbu-taline [196] and piperoxan [197] have been reported by classical gel electrophoresis using sulfated cyclodextrin as a chiral additive, while the separation of the enantiomers of methadone could be successfully achieved by using free-fluid isotachophoresis [198] and by applying a process called interval-flow electrophoresis [199]. 

Pu, Q. S., Fang, Z. L., Combination of flow injection with capillary electrophoresis. Part 6. A bias-free sample introduction system based on electroosmotic-flow traction. Anal. Chim. Actfl 1999, 398(1), 65-74. 

Capillary electrophoresis is based on the same principle as gel electrophoresis. Charged analytes can be separated in an applied electric field according to their mobility. In contrast to gel electrophoresis, however, separations are carried out in a small diameter capillary containing a free solution of electrolyte rather than on a slab gel. Moreover, convective flows due to Joule heating occur more easily in a free solution than in the gel. In contrast to GE, electroosmotic flow is often part of the separation process. 

Free-flow electrophoresis in a continuously flowing film of capillary dimensions (about 0.5 mm). 

Biosample Preparation by Lab-on-a-Chip Devices, Fig. 2 Comparison between (a) batch-mode capillary electrophoresis and (b) continuous-mode free-flow electrophoresis... 

Figure 4 (A) CZE-ESI-MS (negative ionization modus) intensity piot of Suwannee River NOW (ammonium carbonate, pH 10) (B) TIC in timescale (C) CZE-UV (254nm) electropherogram in effective mobility scale of Suwannee River NOM and superimposed electropherograms of selected FFE fractions (measured in CE immediately after FFE separation). (D) FFE-TOC of Suwannee river NOM in effective mobility scale with superimposed weighted (m/z) values as obtained from offline ESI-MS (positive ionization modus) of selected FFE fractions. (Adapted with permission from Schmitt-Kopplin P and Kettrup A (2003) Capillary electrophoresis-elect-rospray ionization-mass spectrometry for the characterization of natural organic matter an evaluation with free flow electrophoresis-off-line flow injection electrospray ionization-mass spectrometry. Electrophoresis 24 3057-3066 Wiley-VCH.)...

Figure 9 Comparison of RP-LC (A) and CZE (B) separations of tryptic peptides of hGH. Peak assignments and correlations for selected fragments are noted. CZE background electrolyte 0.01 mol I Tricine, 0.045 mol I morpholine, 0.02 mol I NaCI, pH 8.0, detection at 200 nm, 316 V cm, 20 pA. LC column Aquapore RP-300 (4.6 x 250 mm), flow rate 1 ml min, detection 214 nm. Solvents A, 0.1% trifluoroacetic acid (TEA) in water B, 0.1% in acetonitrile gradient 0-20% B in 20 min, 20-25%B in 25 min. (Reprinted with permission from Grossman PD, Colburn JC, Lauer HH, et al. (1989) Application of free-solution capillary electrophoresis to the analytical scale separation of proteins and peptides. Analytical Chemistry 61(11) 1186-1194 American Chemical Society.)...

Free-solution capillary electrophoresis (FSCE) is the major technique used for drug analysis, considering the fact that many drugs have acidic or basic groups that allow them to analyzed as charged molecules. In this technique, the capillary is filled with a buffer solution and the separation is based on the different electrophoretic mobilities of the solutes. Separation of both anionic and cationic solutes is possible, owing to electro-osmotic flow (EOF). The pH of the buffer has a major influence on selectivity, but other factors such as buffer concentration, additives, etc. should also be considered dining method development. ... 

ID Separation of Proteins There has been considerable research devoted to tbe development of nricioflu-idic platforms capable of performing small-scale protein separations. In addition to diffusion based methods [3], nearly every type of electrokineticaUy driven separation has been demonstrated in a cbip-based platform, including free-flow electrophoresis, capillary electrophoresis, capillary gel electrophoresis, isoelectric focusing (lEF), micellar electrokinetic chromatography and capillary electrochemical chromatography. 

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