Resolution (chromatography)

This article is about the quantity used in chromatography. For other uses, see Resolution (disambiguation).

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

Example chromatogram showing signal as a function of retention time

Expression

Chromatographic peak resolution is given by

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

where t_R is the retention time and w_b is the peak width at baseline. The bigger the time-difference and/or the smaller the bandwidths, the better the resolution of the compounds. Here compound 1 elutes before compound 2.

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

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

See also

• Image resolution
• Resolution (mass spectrometry)
• Van Deemter equation