Separations and Purifications Flashcards
(16 cards)
Extraction
Solute is isolated based on its dissolution in solvents. You can then separate via density –> drain off the more dense layer. Same thing applies to an organic solvent.
Simple distillation
Separation of liquids based on boiling point. Can be done if the boiling points differ significantly. Done with a normal column.
Fractional distillation
When boiling points of liquids are similar. Uses a fractionating column, which separates through sequentially vaporizes and condenses over and over again.
Vacuum distillation
When chemicals might decompose under high temperatures. This allows you to decrease pressure (vacuum) so that boiling points are lowered.
Mobile phase
Used in chromatography and is the moving part of the setup
Stationary phase
Used in chromatography and is the non-moving part of the setup
Gas chromatography
Stationary phase is a liquid that coats the inside of the pipe. Mobile phase is gas flowing through the pipe. Organic solutes will stick or move according to polarity of stationary phase/mobile phase.
Paper and thin layer chromatography
Special paper is place in a solvent that can move up. Organic solvents are dotted on the bottom and move according to polarity of the stationary phase/mobile phase.
Rf value =
distance traveled by organic solute/distance of the solvent front.
Recrystalization
Dissolve organic crystals in a carefully chosen solvent at a warm temperature. Allow crystals to reform by cooling the solution.
How do you choose a solvent for recrystallization?
The compound of interest should dissolve in the solvent at warm temperatures but not cool temperatures. Helps if impurities are soluble as well.
Two things you can use to determine which molecules will come out of GC the fastest
- Molecular weight –> Molecules that are lighter will be faster. 2. Intermolecular forces –> Anything like hydrogen bonding that will keep a molecule in the column longer?
Quench
Turning a substance that is reactive into something that is less reactive
Ion exchange chromatography
Charged proteins bind to a charged ionic stationary phase. The proteins are then released form the stationary phase by increasing the pH (often NaCl levels), gradually releasing molecules that are less ionic.
Affinity chromatography
Separation using very specific interactions (antigens and antibodies, enzymes and ligands, etc.)
SDS-PAGE (describe SDS and PAGE portions)
Separate proteins based on ONLY size. SDS denatures the protein to get rid of secondary, tertiary, and quaternary structures and makes molecules negative so they move toward the anode. PAGE acts as the forest through which the molecules must run. The smallest will get through first.
