in gas chromatography
https://doi.org/10.1351/goldbook.R05317
A characteristic of the separation of two adjacent peaks. It may be expressed according to the equation: \[R_{\text{AB}} = 2\ \frac{|d_{\text{R}}\left(\text{B}\right)\,-\,d_{\text{R}}\left(\text{A}\right)|}{|w\left(\text{B}\right)\,+\,w\left(\text{A}\right)|}\] where \(R_{\text{AB}}\) is the resolution, \(d_{\text{R}}(\text{A})\) and \(d_{\text{R}}(\text{B})\) are the retention distances (time or volume) of each eluted component A and B, and \(w(\text{A})\) and \(w(\text{B})\) are the respective widths of each peak at its base.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2211 [Terms] [Paper]