Differential Extraction

Principle: Based on the difference in solubility of an organic compound in water and an organic solvent in which it is preferentially more soluble.

Process: Shaking the aqueous solution containing the compound with an immiscible organic solvent in a separatory funnel.

Mass Extracted Formula:

$$w_n = w_0 \left( \frac{V}{V + k \cdot v} \right)^n$$

(where

• $$w_0$$ = initial mass,
• $$w_n$$ = mass remaining after $$n$$ extractions,
• $$V$$ = volume of aqueous solution,
• $$v$$ = volume of organic solvent per extraction,
• $$k$$ = distribution/partition coefficient).
• Key Fact: Multiple extractions with smaller volumes of solvent are more efficient than a single extraction with a large volume.