Origin of Chromatography
When the sample is in the mobile phase the sample moves at the velocity
of the mobile phase; when the sample is in the stationary phase the sample
does not move. Distribution equilibria described by Kd = Cs/Cm
govern the partition between the phases. These movies imagine the sample
as discrete segments which reach equilibria independently. Each segment
moves one position, a new equilibrium is achieved, and the process repeats.
Concentrations for both the stationary and the mobile phase are shown.
These chromatography movies allow you to investigate the effect of
changing K, N, and L on separation and resolution of a two component mixture.
Kd1 = K1 Vs/Vm or approximately the
Kd equilibrium constant for component 1 (shown in red)
Kd2 = K2 Vs/Vm
or approximately the Kd equilibrium constant for component 2 (shown in blue)
N = efficiency (the number of times equilibrium is achieved)
L = column length
Res = Resolution for separation of two peaks = retention difference/average width
Concentration from an instrumental detector like a GC or LC as a function
of time; the x-axis shows how long the component takes to travel the full
length of the column and arrive at the detector. Slower moving components
travel less quickly and arrive at later times.
Retention time = tm (1+K Vs/Vm)
Concentration from an area detector like paper chromatography or TLC
as a function of distance; the x-axis shows the position of the components
at a given time. Slower moving components travel less far and are found
at shorter distances.
Retention distance = dm /(1+K Vs/Vm)