# Retention Factor Formula

Retention factor is very useful chromatographic descriptor since it is dimensionless and independent of the flow rate and column dimensions of mobile phases.

The formula for retention time is given as

k = $\frac{t_{R} – t_{o}}{t_{o}}$ = $\frac{t_{R}}{t_{o}}$.

According to the retention factor, inert tracer which are not absorbed is zero.

According to the retention factor the non absorbed inert tracer is zero. The retention factor has various significance as the most significant quantity that can be derived directly from the chromatogram. It is a partition without dimension or the distribution ratio given by.

k = $\frac{amount~ of~ an~ eluite~ in~ the~ stationary~ phase}{amount ~of~ that~ eluite~ in~ the~ mobile~ phase}$.

## Retention Factor Formula Problems

Question1:If a 125 $\times$ 4.6 mm column and a flow rate of 1 mL min-1. Calculate the estimated dead time.

Solution:

tM = 0.1 $\times$ $\frac{12.5}{1}$ = 1.25

k = $\frac{t_{R}-t_{M}}{t_{M}}$ applies

Solving the equation for tR yields

tR = (tM + 1)k and thus tR = (1.25 + 1)4

t= 9min