Formation of Peak Spacing

Abstract

When two solutes, say 1 and 2, simultaneously injected in a column migrate along the column with different velocities, v 1 and v 2 , their longitudinal distance,from each other, and temporal distancethe difference,is thermal spacing of the peaks. Generally, a closed form solution for Dt R cannot be obtained. A numerical solution can be found from subtraction of numerical solutions of Eqs. (8.27) and (8.28) for t R1 and t R2 . In several practically important special cases, substantial simplifications in evaluations of Dt R or DT R can be made.where v oR is the outlet velocity of the t R -solute at the time t R of its elution. The last formula is based on two assumptions. First, the change in Dz R during the time interval Dt R is negligible compared to Dz R , and, second, the difference between v oR and the outlet velocity, v oR,1 , of the neighboring solute is negligible compared to v oR . Both the assumptions are direct consequence of the properties of the solutes that make them to migrate close to each other. The negative sign in the formula reflects the fact that t R,1 > t R when the t R -solute arrives to the column outlet before its neighbor, and therefore, Dz R ¼ z 1,R À L < 0.An infinitesimally small change, d(Dz), in Dz that takes place during infinitesimally small time interval, dt, when the t R -solute and its neighbor advance from arbitrary locations, z and z 1 to locations z þ dz and z 1 þ dz 1 , respectively, can be 194j 9 Formation of Peak Spacing 9.2 Closely Migrating Solutes in Dynamic Analysis j195