phase ratio, β

in chromatography
The ratio of the volume of the mobile phase to that of the stationary phase in a column:
β = V 0 V s
In the case of open-tubular columns the geometric internal volume of the tube (V c) is to be substituted for V 0.
PAC, 1993, 65, 819 (Nomenclature for chromatography (IUPAC Recommendations 1993)) on page 833
Orange Book, p. 100