Fraktionointi

Fraktionointi, or fractionation, is the process of separating a heterogeneous mixture into fractions that differ in a specified property, enabling analysis, purification, or further processing. The term covers a broad set of techniques that exploit contrasts such as boiling point, solubility, molecular size, charge, or affinity.

In chemistry and chemical engineering, fractional distillation separates liquids with different boiling points by repeated vaporization and condensation in a fractionating column. Fractional crystallization isolates compounds based on differential solubility and crystallization kinetics. Chromatographic methods, including column chromatography and gas or liquid chromatography, separate components according to their partitioning between a stationary phase and a mobile phase. Centrifugation uses centrifugal force to separate mixtures by density.

In biochemistry and cell biology, cell fractionation employs differential centrifugation to partition cellular contents into subcellular components such as nuclei, mitochondria, and ribosomes. Protein and nucleic acid fractionation use precipitation, ion-exchange, affinity chromatography, and gel filtration to enrich or isolate specific biomolecules.

In industry and environmental science, fractionation underpins petroleum refining, food processing, and waste treatment, where mixtures are divided into usable or more easily managed fractions. The choice of method depends on the sample’s properties, the desired level of purity, throughput, and cost.

Practical considerations include maintaining sample stability, minimizing losses and cross-contamination, and validating fractions with analytical techniques to confirm identity and quality.