# Plate Theory and Extensions - The Retention Volume of a Solute > Page 12

Thus,
V_{r} = n(v_{m }+ Kv_{s})

= nv_{m} + KV_{s}

_{ }

The volume of
mobile phase per plate (v_{m}), multiplied by the number of plates (n),
will give the total volume of mobile phase in the column (V_{m}).
Similarly, the volume of stationary phase per plate (v_{s}), multiplied
by the number of plates (n), will give the total volume of stationary
phase in the column (V_{s}).

Thus,
** V _{r = }V_{m }+ KV**

_{S }_{ (13)}

_{ }

*The function for the retention volume is indeed simple and
depends solely on the distribution coefficient and the volumes of the two
phases that are present in the column.*

For an
unretained beak K=0 and V_{r}_{(0)} =
V_{m}