adsorption isotherm

[olivia]

Hi, can anyone explain to me how the adsorption isotherm relates to chromatography.
I am really stuck, and I am trying to read up on all the theory, but this one is confusing me!
Thanks

Liv

[tom jupille]

A distribution isotherm is a plot of the concentration of analyte in (or on) the stationary phase (y-axis) versus the concentration of analyte in the mobile phase (x-axis).

The slope of the isotherm is the distribution coefficient for the analyte at that concentration, and is therefore proportional to k'. The disitribution coefficient therefore describes how k' changes as a function of analyte concentration.

An adsorption isotherm is a special case where the stationary phase is considered to be a surface, but the concept is general.