Capillary zone electrophoresis charge/mass/ratios

In CZE, the capillary, inlet reservoir, and outlet reservoir are filled with the same electrolyte solution. This solution is variously termed background electrolyte, analysis buffer, or run buffer. In CZE, the sample is injected at the inlet end of the capillary, and components migrate toward the detection point according to their mass-to-charge ratio by the electrophoretic mobility and separations principles outlined in the preceding text. It is the simplest form of CE and the most widely used, particularly for protein separations. CZE is described in Capillary Zone Electrophoresis. ... 

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 zone electrophoresis is the simplest and most widely used mode in CE. Separations in CZE are based on mobility differences between the analytes in an electric field. These differences are dependent on the size and charge-to-mass ratio of the analyte ion. 

Capillary zone electrophoresis (CZE), also known as free-solution CE, is the most widely used mode of CE essentially because of its versatility. Protein separation in CZE is based on the differential electrophoretic mobility of the analytes. This mobility is primarily dependent on a protein s size and net charge, the charge-to-mass ratio. Solvent properties that influence the size and charge of a protein include pH, ionic strength, viscosity, and dielectric constant.67 Manipulation of these properties, most notably pH, dictates the selectivity in CZE. Maximizing the charge difference between two proteins via pH modification optimizes their separation. 

The fundamental separation mechanism of capillary zone electrophoresis (CZE) is based on differences in the mobilities of solutes. Mobility is defined as the charge/mass ratio for each solute. Since the charge is often a function of pH, the pH is the most important adjustable parameter for control of resolution. The order of elution on bare silica at high pH is cations, unseparated neutrals, and anions. At low pH, where the EOF is very low, the anions may migrate toward the positive electrode and may not be seen using normal polarity. 

Capillary Zone Electrophoresis (CZE). CZE is a widely used CE technique and separates peptides and proteins based on differences in their charge-to-mass ratios. Separations occur in a capillary filled with a buffer of constant composition. For CZE, the run buffer choice is extremely important because it determines the charge on the analyte molecule and its migration rate. Thus, the type of buffer, its ionic strength, and its pH are optimized for particular separation problems. Buffers based on sodium phosphate, citrate, acetate, or combinations thereof with concentrations ranging from 10 to 200 mM are frequently used [14]. 

Capillary zone electrophoresis, CZE, is the simplest CE mode in which the separation is based on differences in the charge-to-mass ratio of the analytes. This approach can be effective in a number of applications in particular, quaternary alkaloids owing to the permanent charge are ideal solutes in CZE, regardless of the pH of the running buffer. Below, the most important parameters affecting the CZE separation will be considered with emphasis on the relevant aspects involved in analysis of alkaloids in herbal drugs and medicinal plants. 

In 1996, the capillary zone electrophoresis (CZE) separation of a model mixture of six anthocyanins was reported using a 150-mM borate buffer at pH 8 (Bridle et al., 1996). It was proposed that the separation was influenced by three factors electro-osmotic flow (EOF), charge/mass ratio, and complex formation with borate. Bridle and Garcia-Viguera (1997) compared HPLC and CZE for the separation of strawberry and elderberry anthocyanins. They used fused-silica capillaries (57 cm X 75 fim i.d.), mn at 25°C with 150 mM sodium borate buffer (pH 8.0). A more concentrated sample (87 times) was needed for equivalent CZE response at pH 8 compared to HPLC at pH 1.8 because of the much smaller sample introduction volume, the shorter detector ceU path length, and the smaller proportion of colored anthocyanin species at pH 8.0. The separation of strawberry anthocyanins by CZE was satisfactory but the separation of elderberry anthocyanins by CZE was marred by the presence of a large baseline hump. The baseline rise may have been caused by interfering compounds in the extract (i.e., colored polymers) which did not affect the... 

Capillary zone electrophoresis (CZE) is the most commonly used separation mode in CE microchip due to its versatility, ease of operation, and separation power. This electrophoretic mode is based on the theory and mechanism of action directly transferred from the conventional CE. In CZE the channel contains only a buffered medium and the electrophoretic mobilities of the analytes depend on their charge/mass ratio, acting as separation mechanism. These different velocities make possible to separate cations and anions if the EOF is strong, in order to lead anionic substances to the detector located usually at the cathode. It has the limitation of being useful only for separation of charged species. 

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