# Dispersion in Chromatography Columns - The Van Deemter Equation > Page 45

# The Van Deemter Equation

The Van Deemter
equation (9) was derived as long ago as 1956 and was the first rate equation to
be developed. There are, however, a number of alternative rate equations that
have been reported, but when subjected to experimental test, the Van Deemter
equation has been shown to be the most appropriate equation for the accurate
prediction of dispersion in chromatographic systems. The Van Deemter equation
is particularly pertinent at mobile phase velocities around the optimum*
velocity* (a concept that will shortly be explained). Consequently, as all
columns should be operated at, or close to, the optimum velocity for maximum
efficiency, the Van Deemter equation is particularly important in column
design.

Restating the Van Deemter equation,

_{}

** **

where f_{1}(k") = _{} and
f_{2}(k") = _{}