fraction extracted, E in chromatography
The fraction of the total quantity of a substance extracted (usually by the solvent) under specified conditions, i.e. E A = Q A Q A ' where Q A is the mass of A extracted and Q A ' is the total mass of A present at the start.
  1. E may be expressed as a percentage, % E.
  2. The term extractability is qualitative and should not be used as a synonym for fraction extracted.
  3. If the aqueous phase is extracted with n successive portions of solvent, the phase volume ratio (solvent/feed) being r each time, the fraction extracted is given by:
    E n = 1 − ( r D + 1 ) − n
    If n = r = 1 and E 1 = D 1 + D this expression is a concept of value in chromatography theory.
  4. The fraction extracted is also known as the recovery factor, especially for a multistage process.
PAC, 1993, 65, 2373 (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2384