# Resolution (chromatography)

Example chromatogram showing signal as a function of retention time

In chromatography, resolution is a measure of the separation of two peaks of different retention time t in a chromatogram.[1][2][3][4]

## Expression

Chromatographic peak resolution is given by

${\displaystyle R_{s}=2{\cfrac {t_{R2}-t_{R1}}{w_{b1}+w_{b2}}}}$

where tR is the retention time and wb is the peak width at baseline. Here compound 2 elutes before compound 1.

If the peaks have the same width

${\displaystyle R_{s}={\cfrac {t_{R2}-t_{R1}}{w_{b}}}}$ .

## Plate number

Two resolved peaks in a chromatogram

The theoretical plate height is given by

${\displaystyle H={\frac {L}{N}}}$

where L is the column length and N the number of theoretical plates.[5] The relation between plate number and peak width at the base is given by

${\displaystyle N=16\cdot \left({\frac {t_{R}}{W_{b}}}\right)^{2}\,}$ .