interparticle volume of the column, V0 

in chromatography
https://doi.org/10.1351/goldbook.I03116
The volume occupied by the mobile phase between the particles in the packed section of a column. It is also called the interstitial volume or the void volume of the column. In liquid chromatography, the interparticle volume is equal to the mobile-phase hold-up volume (VM) in the ideal case, neglecting any extra-column volume. In gas chromatography, the symbol VG may be used for the interparticle volume of the column. In the ideal case, neglecting any extra-column volume, VG is equal to the corrected gas hold-up volume (VMo). VG=VMo=VMj
Source:
PAC, 1993, 65, 819. (Nomenclature for chromatography (IUPAC Recommendations 1993)) on page 832 [Terms] [Paper]