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 ($V_{\text{M}}$) in the ideal case, neglecting any extra-column volume. In gas chromatography, the symbol $V_{\text{G}}$ may be used for the interparticle volume of the column. In the ideal case, neglecting any extra-column volume, $V_{\text{G}}$ is equal to the corrected gas hold-up volume ($V_{\text{M}}^{\text{o}}$). $$V_{\text{G}}=V_{\text{M}}^{\text{o}}=V_{\text{M}j}$$