# Extra Column Dispersion - Dispersion in Contemporary LC Columns > Page 4

# Dispersion in Contemporary LC Columns

The standard
deviation volume of an eluted peak (s_{v})
is given by, (see
Plate Theory and Extensions),

_{}

where, (V_{r)} is the retention volume of the solute
and (n) is the column efficiency.

Now, V_{r}
= V_{o}(1+k') = elpr^{2}(1+k')

where (V_{o}) |
is the thermodynamic dead volume of the column, (i.e.,V_{o}=elpr^{2}(1+k')) |

(r) | is the radius of the column, |

(l) | is the length of the column, |

and (e) | is the fraction of the mobile phase in the column that is available to the solute |

Consequently, _{}

Now _{}

Now, for a
well packed column H = 1.6 d_{p}, where (d_{p}) is the particle
diameter of the packing (1)