Final answer:
Using several small portions of solvent in liquid-liquid extractions is more efficient due to better maintenance of a concentration gradient and repeated disturbance of equilibrium, both of which favor the transfer of the solute to the solvent phase.
Step-by-step explanation:
When performing liquid-liquid extractions (LLE), using several small portions of solvent rather than one large volume is more efficient due to the principles of equilibrium and partitioning behavior of solutes. With each successive extraction using a fresh portion of solvent, the extraction efficiency is optimized because you repeatedly disturb the equilibrium, facilitating the transfer of solute into the solvent phase as dictated by Le Chatelier's principle. As more solvent is added in dilution, the concentration of solute decreases, making it less efficient to extract with a single large volume of solvent.
Furthermore, by using smaller volumes sequentially, the solvent maintains a higher concentration gradient favoring the transfer of the solute from one phase to the other, which tends to increase the overall extraction efficiency. Additionally, methodologies like automated LLE coupled with LC-MS/MS leverage these principles to increase efficiency, reduce costs, and enhance throughput in analyzing pharmaceutical moieties.