fraction extracted, E

The fraction of the total quantity of a substance extracted (usually by the solvent) under specified conditions, i.e. $Math - ei$ where $Math - text$ is the mass of A extracted and $Math - text$ is the total mass of A present at the start.

Notes:

$Math - note$ may be expressed as a percentage, $Math - note$ .
The term extractability is qualitative and should not be used as a synonym for fraction extracted.
If the aqueous phase is extracted with $Math - note$ successive portions of solvent, the phase volume ratio (solvent/feed) being $Math - note$ each time, the fraction extracted is given by:
$Math - e$
If $Math - ei$ and $Math - ei$ this expression is a concept of value in chromatography theory.
The fraction extracted is also known as the recovery factor, especially for a multistage process.

Source:

PAC, 1993, 65, 2373 (Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)) on page 2384