extracties

Extracties is a term used for processes that separate a substance from a mixture by preferentially dissolving it in a second immiscible solvent. The method relies on differences in solubility between phases to move the target compound from one phase into another. In chemistry and analytical chemistry, extracties are widely used for isolation, purification, and concentration of chemicals, as well as sample preparation for further analysis.

Common techniques include liquid-liquid extraction (LLE), which transfers solute between immiscible liquids, typically water and an organic solvent; solid-phase extraction (SPE), which uses a solid sorbent to bind the solute and release it later; and newer methods such as supercritical fluid extraction (SFE) using supercritical CO2, and solid-phase microextraction (SPME) that minimizes or eliminates solvent use. The choice of method depends on the target compound, the matrix, and practical factors such as solvent compatibility and safety.

Key concepts include the distribution (or partition) coefficient, pH control to favor the extraction of ionizable compounds, and temperature effects on solubility. Process design ranges from batch extractions to continuous, countercurrent, multi-stage operations aimed at increasing yield and selectivity. Practical issues include emulsions, incomplete phase separation, and the need for back-extraction or stripping to recover the solute in the desired phase.

Applications span laboratory sample preparation, environmental analysis of water and soil pollutants, pharmaceutical and food processing, and natural product isolation. In biology and medicine, extraction also refers to isolating biomolecules such as DNA, RNA, or proteins from cells, often involving lysis, removal of contaminants, and precipitation or chromatography.

Safety and environmental considerations emphasize solvent toxicity and flammability, the use of greener solvents where possible, and waste management.