mass distribution ratio in chromatography, in micellar electrokinetic chromatography

https://dx.doi.org/10.1351/goldbook.M03718
The fraction (1 − R) of a component in the stationary phase divided by the fraction (R) in the mobile phase:
D m = amount of substance in the stationary phase amount of component in the mobile phase
This term is recommended in preference to the term capacity factor frequently used in the chromatographic literature.
Source:
PAC, 1993, 65, 2373 (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2384