interparticle porosity, \(\epsilon\)

in chromatography
https://doi.org/10.1351/goldbook.I03115
The interparticle volume of a packed column per unit column volume: \[ɛ=\frac{V_{0}}{V_{\text{c}}}\] It is also called the interstitial fraction of the column.
Source:
PAC, 1993, 65, 819. (Nomenclature for chromatography (IUPAC Recommendations 1993)) on page 832 [Terms] [Paper]