Purnell equation

The Purnell equation is an equation used in analytical chemistry to calculate the resolution R_s between two peaks in a chromatogram. ^{[1] [2]}

${\displaystyle R_{s}={\frac {\sqrt {N_{2}}}{4}}\left({\frac {\alpha -1}{\alpha }}\right)\left({\frac {k'_{2}}{1+k'_{2}}}\right)}$

where

R_s is the resolution between the two peaks

N₂ is the plate number of the second peak

α is the separation factor between the two peaks

k '₂ is the retention factor of the second peak.

The higher the resolution, the better the separation.

References

1. Purnell, J.H. (1960). "The correlation of separating power and efficiency of gas-chromatographic columns". J. Chem. Soc.: 1268–1274. doi:10.1039/JR9600001268.
2. Skoog, D.A.; Holler, F.J.; Nieman, T.A. (1998). Principles of instrumental analysis. Belmont, CA: Brooks/Cole. p. 689.