**Velocity of migration of analytes:**

This is a simple derivation of analyte migration velocity for a typical chromatographic system. Use with lecture presentation.

Let the linear velocity of the m.p. = u

Assume instantaneous equilibration and the number of moles of the analyte
in m.p and s.p. respectively are m_{m} and m_{s}.

Noting that if no retention the analyte will move at u and the retention is due to partitioning into the s.p.

The velocity of an analyte, v, will then be,

where, V_{s}, V_{m}, K are volume of the stationary phase,
volume of the mobile phase, partition coefficient of the analyte and L
is the length of the column. The subscript i refers to the analyte i. For
a given chromatographic system run under a constant set of physical conditions
(which includes the materials of sp and mp), factors governing analyte migration
velocity are the same for all analytes except K_{i}. Therefore each
analyte will acquire a unique migration velocity depending on its partition
coefficient.