Band velocity

Thus the band velocity (Z) is inversely proportional to (Vm + KVs), and for a significantly retained solute, Vm KVs, consequently. 

It is seen from the above equation that the band velocity is inversely proportional to the distribution coefficient with respect to the stationary phase. It follows that any changes in the distribution coefficient (K) will result directly in changes in the band velocity (Z). Consequently, if the isotherm is linear, then all concentrations will travel at the same velocity and the peak will be symmetrical. 

This equation allows the retention time (or solute band velocity) to be calculated from the equilibrium distribution coefficient K, and vice versa. 

In a uniform colonm the isothermal retention volume V is related to eluent-gas flow rate F, column length L, and average band velocity (dzjdtXy, by the expression... 

For the gradient case where k Is generally changing throughout, the Instantaneous band velocity Is of Interest. It follows from Equation 8 that Dband.lnst found In terms of the... 

Anonymous (1987). Corrsin, Stanley. Who s who in America 44 584. Marquis Chicago. Comte-Bellot, G., Corrsin, S. (1971). Simple Eulerian time correlation of fuU and narrow band velocity signals in grid-generated isotropic turbulence. J. FluidMech. 48(2) 271-337. Corrsin, S. (1951). The decay of isotropic temperature fluctuations in an isotropic turbulence. 

Consider a distribution system that consists of a gaseous mobile phase and a liquid stationary phase. As the temperature is raised the energy distribution curve in the gas moves to embrace a higher range of energies. Thus, if the column temperature is increased, an increasing number of the solute molecules in the stationary phase will randomly acquire sufficient energy (Ea) to leave the stationary phase and enter the gas phase. As a result, the distribution coefficient with respect to the stationary phase of all solutes will be reduced as the temperature rises and it will be seen in due course that this will cause the band velocity of all the solutes to be increased. 

In addition to adjusting band velocity, one noay adjust column length to achieve initial sample retention. Increases in column length will usually improve separations of several components also, since retention times are proportional to L, the column length, while band broadening increases roughly as. ... 

Figure 10.13 Pictures illustrating segregation results in the sheared band within a split-bottom cell, (a) Sketch of a split-bottom cell Q is the rotation speed of the base, (b) Sketch of bulk shear band (black area), (c) Measured surface velocity as a function of radial position (symbols) for 1 and 3 mm glass particle mixtures described in Hill and Fan (2008). The solid line is the shear band velocity described by Fenistein et al. (2004) (d) The radial dependence of cu = u/r and u = rduoldr. (Continued)...

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