Fraction of the intraparticle volume (the volume of the pores) available to the molecules of a particular sample component for diffusion:
\[K_{0} = \frac{V_{\rm{R}} - V_0}{V_{\rm{i}}}\]Notes: - The value of \(K_{0}\) varies between zero and unity. For an unretained compound, \(V_{\rm{R}} = V_{0}\) and thus, \(K_{0} = 0\). On the other hand, for a compound the molecules of which are smaller than the smallest pores, \(V_{\rm{R}} = V_{\rm{t}}\) and thus, \(K_{0} = 1\).
- In exclusion chromatography, \(K_{0}\) is related to the retention volume of a sample component and the inter- and intraparticle volumes of the column (\(V_{0}\) and \(V_{\rm{i}}\), respectively) in a manner analogous to the relationship in general liquid chromatography: \[V_{\rm{R}} = V_{0} + K_{0}V_{\rm{i}}\]
Source:
PAC, 2017, 90, 181. 'Terminology of separation methods (IUPAC Recommendations 2017)' on page 211 (https://doi.org/10.1515/pac-2017-0111)