This term may be used in place of liquid-liquid distribution when the emphasis is on the analyte(s) being distributed (or extracted).
The distinction between the @[email protected] (\(K_{\text{D}}\)) and the @[email protected] (\(K_{\text{D}}^{\text{o}}\)) or the concentration distribution ratio  (\(D_{\text{c}}\)) is reaffirmed and it is recommended that the terms @[email protected], @[email protected] and @[email protected] constant should not be used as synonyms for the (analytical) @[email protected], \(D_{\text{c}}\). A distinction is drawn between the terms solvent and diluent, and the term @[email protected] is now restricted to the active substance in the solvent (i.e. the homogeneous 'organic phase' which comprises the @[email protected], the diluent and/or the modifier) which is primarily responsible for the transfer of solute from the 'aqueous' to the 'organic' phase.
Orange Book, 2nd ed., p. 88 [Terms] [Book]