Separation of Immiscible Liquids and Chromatography

Liquid-Liquid Separation

• Separation of two or more immiscible liquids or solvents is best done using differential extraction with a separating funnel.
• Distillation methods used include vacuum, steam, fractional, destructive, and simple distillation.

Chromatography

• Chromatography techniques used include thin layer, gas, paper, column, and HPLC.
• Retention factor is a key concept in chromatography.
• Mobile phase and stationary phase (solid) are essential components of chromatography.
• Stationary phase can be either polar or non-polar, e.g., cellulose, silica gel, alumina.
• Rf value is calculated by dividing the distance of the sample by the distance of the solvent.

Purification of Organic Compounds

• Organic compounds need to be purified to obtain a useful product for applications such as pharmaceuticals, biomedicals, tissue engineering, and cosmetics.
• Separation techniques used depend on the nature of the mixture, which can be miscible or immiscible.
• Mixtures can be classified into four types: liquid-liquid (miscible), solid-solid (miscible), solid-solid (immiscible), and liquid-solid (miscible or immiscible).

Separation Techniques

• Liquid-liquid (miscible): simple distillation or chromatography are the best methods.
• Solid-solid (miscible): sublimation is the best method of separation.
• Solid-solid (immiscible): winnowing and magnetic separation are the best methods.
• Liquid-solid (miscible): evaporation, crystallization are the best separating methods.
• Liquid-solid (immiscible): decantation, filtration, sedimentation are the best methods.

Crystallization

• Crystallization is based on the difference in solubility of the compounds and their impurities.
• Impure compound is dissolved in a solvent in which it is partially soluble at room temperature but appreciably or completely soluble at higher temperatures.
• Solution is concentrated to get a nearly saturated solution, and on cooling, the compound crystallizes out and is removed by filtration.
• Colored impurities in the solution can be removed by adsorption using activated charcoal.
• Example: impure benzoic acid can be purified by dissolving in hot water, adding activated charcoal to adsorb impurities, filtering the solution, and then crystallizing the solution by allowing it to cool down.