Extraction liquide-liquide : théorie, applications, difficultés

Abstract

Liquid-liquid extraction (LLE) methods allow transfer of compounds solubilized in a liquid phase into another immiscible liquid phase. These methods are routinely used in pharmacology/toxicology so as to purify and concentrate biological samples before chromatographic analysis. Many different physico-chemical properties of sol- vents and solutes have to be taken into account in LLE. To perform an extraction, the choice of a solvent or of a mixture of solvents depends on their miscibility with water, proticity, dielectric constant, dipole moment, density, volatility and toxicity. In the same way, the evaluation of properties of solutes such as structure, acidity constant and lipophily, to- gether with the nature and complexity of the matrix, will allow the optimization of the extraction process. Its efficiency will be evaluated with the extraction recovery. The influence of these parameters will be discussed in this review, and the different extraction processes (single, multiple, back-extraction and ion-pair formation) will be described with their respective advantages and drawbacks. The control of all these variables should allow the operator to optimize LLE during development of analytical methods in pharmacology/toxicology.