ABSTRACT
II. FACTORS THAT CAUSE BAND-BROADENING The resulting separation, the resolution, depends on both selectivity and band-broadening. By introducing various porosity or interacting groups onto the surface of the stationary phase, biopolymers can be separated according to size, surface, charge, hydrophobicity, and three-dimensional substructure. Band-broadening in a packed column of porous supports is often expressed by the van Deemter equation [6]:
B H =A+-+emv+e 8 v v (1)
where H is the plate height and A, B/v, em v, and es v are lumped terms that account for band-broadening resulting from eddy diffusion, longitudinal diffusion, and nonequilibrium mass transfer in the mobile and the stationary phases, respectively. The dependency of plate height H on flow rate v is shown in Fig. 1. The curve shows a minimum value of the plate height Hmin at mobile phase velocity vmin. Below this optimum velocity, His dependent on the B term of the van Deemter equation. At higher velocity, the mass-transfer terms em and es become the controlling factors.
