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 K_d = C_s/C_m 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.

One Component

Two Components

Chromatograms

These chromatography movies allow you to investigate the effect of changing K, N, and L on separation and resolution of a two component mixture.

K_d1 = K₁ V_s/V_m or approximately the K_d equilibrium constant for component 1 (shown in red)
K_d2 = K₂ V_s/V_m or approximately the K_d 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

Time Units

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 = t_m (1+K V_s/V_m)

Change K

Change N

Change L

Distance Units

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 = d_m /(1+K V_s/V_m)

Change K

Change N

Change L

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Chemical Equilibrium  | Beloit College Chemistry Department
If you click on the movie you can then use the left and right arrow keys to control views.