## distribution ratio, $$D$$

in liquid-liquid distribution
https://doi.org/10.1351/goldbook.D01817
The ratio of the total analytical concentration of a solute in the extract (regardless of its chemical form) to its total analytical concentration in the other phase.
Notes:
1. If there is possible confusion with the @E02305@ or (mass) distribution ratio the term concentration distribution ratio (symbol $$D_\text{c}$$) should be used, but this is not common usage. This is reasonably compatible with chromatographic nomenclature.
2. The terms @D01812@, @E02303@ and, where appropriate, @S05511@ @C01124@, @S06054@ @C01124@ are widely used alternatives but are not recommended. If they must be used in a given situation the term ratio is preferable to @C01124@.
3. In equations relating to aqueous/organic systems the organic phase concentration is, by convention, the numerator and the aqueous phase concentration the denominator. In the case of @S06054@ ratio the opposite convention is sometimes used but should then be clearly specified.
4. In the past there has been much confusion between the distribution ratio as defined above, the value of which varies with experimental conditions, e.g. $$\text{pH}$$, presence of complexing agents, extent of achievement of equilibrium etc. and the true @P04437@ which is by definition invariable or the @P04437@ or @D01813@ which apply to a particular chemical species under specified conditions. For this reason the terms @D01813@, @P04438@, @P04437@, @P04440@ and @E02301@ constant should not be used in this context.
5. The use of the ratio: light phase concentration to heavy phase concentration is ambiguous and is not recommended.
6. The distribution ratio is an experimental parameter and its value does not necessarily imply that distribution equilibrium between the phases has been achieved.
Sources:
Orange Book, 2nd ed., p. 89 [Terms] [Book]
PAC, 1993, 65, 2373. (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2382 [Terms] [Paper]
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 970 [Terms] [Paper]