# Retention Factor Formula

Retention factor some\times called capacity factor is a very convenient chromatographic descriptor since it is dimensionless and independent of the mobile phase flow rate and column dimensions.

## Retention Factor Formula Problems

**Some of the solved problems based on Retention Factor Formula are given below.**

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

**Solution:**t

_{M}= 0.1 $\times$ $\frac{12.5}{1}$ = 1.25

_{R}yields

_{R}= (t

_{M}+ 1)k and thus t

_{R}= (1.25 + 1)4 =

**9 min**

**Question 2: **The k value is a multiple of the value of the dead time. How many \times the dead time is the retention time? For a substance that elutes after 4min on a 125$\times$4mm column at a flow rate of 1mL min^{-1}, the k value is 4. If a flow rate of 2mL min^{-1} the substance would also elute after 4 min, the k value would be 8.

**Solution:**

_{M}in the first case,

_{M}= 0.08 $\frac{12.5}{1}$ = 1.25 retention time equals 4 \times the dead time 4$\times$1 = 4

_{M}in the second case,

_{M}= 0.08 $\frac{12.5}{2}$ = 0.5 retention time equals 8 \times the dead time 8$\times$0.5 = 4