Electrophoretic mobility diameter

The choice of the FFF technique dictates which physicochemical parameters of the analyte govern its retention in the channel FIFFF separates solely by size, SdFFF by both size and density, ThFFF by size and chanical composition, and EIFFF by mass and charge. The dependence of retention on factors other than size can be advantageous in some applications, and different information can be obtained by employing different techniques in combination or in sequence. On the other hand, the properties that can be characterized by FFF include analyte mass, density, volume, diffusion coefficient, charge, electrophoretic mobility, p/ (isoelectric point), molecular weight, and particle diameter. 

Particles of Fe203 with an average diameter of 1 /un were dispersed in xylene containing 5 x 10 3 mole liter 1 of copper(I) oleate. These showed an electrophoretic mobility of 0.110 fim s V-1 cm. The conductivity of the solution was 4.7 x 10 10 ohm cm-1, indicating an ion... 

Figure 26-31 Separation of natural isotopes of 0.56 mM Cl by capillary electrophoresis with indirect spectrophotometrlc detection at 254 nm. Background electrolyte contains 5 mM CrOJ to provide absorbance at 254 nm and 2 mM borate buffer, pH 9.2. The capillary had a diameter of 75 m, a total length of 47 cm (length to detector = 40 cm), and an applied voltage of 20 kV. The difference in electrophoretic mobility of 36C and 37CI is just 0.12%. Conditions were adjusted so that electroosmotlc flow was nearly equal to and opposite electrophoretic flow. The resulting near-zero net velocity gave the two isotopes maximum time to be separated by their slightly different mobilties. [From C. A Lucy and T. L McDonald, "Separation of Chloride Isotopes by Capillary 35 40 45 Electrophoresis Based on the Isotope Effect on Ion Mobility"Anal.

Counterion nm-diameter polystyrene latex (0.35% solids) Electrophoretic Mobility, ym cm/volt sec a... 

The Effect of NaCl on the Electrophoretic Mobility of PS Latex Particle. The em of the Dow 357 nm latex in the H-form and Na-form, along with two other Dow monodisperse latexes in the H-form with diameters of 795 and 1100 nm, was measured as a function of NaCl concentration. The results in Figure 1 show that the em for all three latexes increased with increasing concentration of NaCl to a maximum at about 1 x 10 "2 M NaCl followed by a rapid decrease. Converting the electrophoretic mobility to zeta potential, using tables derived by Ottewill and Shaw (6) from the results of Wiersma et al. in order to account for relaxation and retardation effects, led to the same dependency as shown in Figure 2. 

A spherical molecule of diameter 40.0 A in a dilute aqueous solution at 20°C (17 = 0.0100 poise) carries an effective charge of 3 units (z = 3). What is the magnitude of its velocity in an electrical field of strength 50.0 V/cm What is its electrophoretic mobility ... 

The size and charge analysis was done using a Coulter DELSA 440SX (Coulter Beckman Corp., Miami, FL). This particular instrument measured the size distribution on the basis of photon correlation spectrometry (PCS) and was limited to particle diameters between 0.02 pm and 3 pm. Measurements were taken at four different angles simultaneously with 256-channel resolution each. Comparison of the spectra allowed for the detection of very small particles. The zeta potential was assessed on the basis of electrophoretic mobility (laser Doppler anemometry, LDA). This was defined as the particle velocity per unit of applied electrical field, with units usually given as pm s 1/V cm-1, while zeta potential is defined as the electrical potential between the bulk solution and the... 

Table 1. Relationship between X and the physical solute properties using different FFF techniques [27,109] with R=gas constant, p=solvent density, ps=solute density, co2r=centrifugal acceleration, V0=volume of the fractionation channel, Vc=cross-flow rate, E=electrical field strength, dT/dx=temperature gradient, M=molecular mass, dH=hydrodynamic diameter, DT=thermal diffusion coefficient, pe=electrophoretic mobility, %M=molar magnetic susceptibility, Hm=intensity of magnetic field, AHm=gradient of the intensity of the magnetic field, Ap = total increment of the chemical potential across the channel...

Capillary electrochromatography uses electroendosmotic flow (EOF) to perform highly efficient separations in small-diameter fused-silica capillaries, packed with HPLC-type stationary phases. It can be considered as a combination of capillary electrophoresis (CE) and HPLC. The separation of solutes is based on electrophoretic mobility (for charged species) and interaction with the stationary pha.se, allowing the separation of both neutral and charged compounds. 

The velocity of a solute in the capillary is determined by its electrophoretic mobility and electro-osmotic flow (EOF), which are affected by temperature, and which is influenced by the diameter and length of the capillary, its contents, concentration, and pH of running buffer, applied voltage, current, viscosity, and zeta-potential. The subtle variation of EOF is also a main factor in maintaining high reproducibility if CE is automated by the constant temperature of the capillary and running buffer with proper buffering capacity. However, it is difficult to keep the temperature constant, as EOF depends on the condition of the fused silica. 

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