Chromatography packed particles, radius

As the first term of the right-hand side of Equation 11.20 is independent of fluid velocity and is proportional to the radius fg (m) of particles packed as the stationary phase under usual conditions in chromatography separation, Hs (m) will increase linearly with the interstitial velocity of the mobile phase u (m s ), as shown in Figure 11.9. With a decrease in the effective diffusivities of solutes (m s ), Hs for a given velocity will increases, while the intercept of the straight lines on the y-axis, which corresponds to the value of the first term of Equation 11.20, is constant for different solutes. The value ofthe intercept will depend on the radius of packed particles, but does not vary with the effective diffusivity of the solute. 

Chromatographic approaches have been also used to separate nanoparticles from samples coupled to different detectors, such as ICP-MS, MS, DLS. The best known technique for size separation is size exclusion chromatography (SEC). A size exclusion column is packed with porous beads, as the stationary phase, which retain particles, depending on their size and shape. This method has been applied to the size characterization of quantum dots, single-walled carbon nanotubes, and polystyrene nanoparticles [168, 169]. Another approach is hydro-dynamic chromatography (HDC), which separates particles based on their hydro-dynamic radius. HDC has been connected to the most common UV-Vis detector for the size characterization of nanoparticles, colloidal suspensions, and biomolecules [170-172]. 

In a gel chromatography column packed with particles of average radius 22 pm at an interstitial velocity of 1.2 cm min- of the mobile phase, two peaks show poor separation characteristics, that is, =0.85. 

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