**Definition:
Capacity factor**

The **capacity
factor** (also called "capacity ratio") is symbolized by **k'**
(USP terminology) or **k** (IUPAC/ASTM terminology). It is a
measure of the retention of a peak that is independent of column
geometry or mobile phase flow rate.

The capacity factor
is calculated as:

**k' = (t****R - t0)/t0**

where **t****R** is the retention time of
the peak, and** t****0 **is the dead time of the column.

Note that the
capacity factor cannot be calculated in this manner from a gradient
chromatogram. The "apparent" capacity factor obtained when this is done
is meaningless chromatographically.