Theoretical analysis of the behavior of a centrally injected band in a homogeneous chromatographic column

A new implementation of the equilibrium-dispersive model permits the study of problems requiring two-space dimensions for their modeling, such as a no nhomogeneous column with a cylindrical symmetry, a nonplanar injection with a cylindrical symmetry, or a cylindrical central injection. The migration and broadening of a cylindrical band coaxial with the column but narrower, moving along a homogeneous column is studied. The axial and radial profiles of the band inside the column and the elution profiles are calculated. The se profiles depend on both the radial and the axial dispersion coefficients . The radial dispersion coefficient decreases with increasing mobile phase velocity and is usually low, much lower than the axial dispersion coefficie nt. Thus, the material in a relatively wide central injection made on a wid e bore column may never have a chance to get close to the column wall. The clearance required at injection is estimated. (C) 1998 Elsevier Science B.V . All rights reserved.