Exp 1: Extraction Caffeine

Extraction

Common separation technique in organic chemistry which is directed at separating the components of a mixture.

“like dissolves like”

Extraction follows this concept

Extraction process

Gerally based on the solubility of a particular substance present in a given sample to a specific solvent.

Extraction

Be viewed as the transfer of specific solutes from one phase (i.e., solid phase) to another one (i.e., liquid phase)

Simple Extraction

one-time extraction process using a single solvent to separate components within a given time.

Multiple Extraction

• Repetitive extraction process where a single solvent is used multiple times to extract more amount of a particular solute.

• It can also use multiple solvents which enables the process to extract multiple components from a given sample mixture

Solid-Liquid Extraction

Transfer of target solute from a solid phase to a liquid phase (e.g., extraction of caffeine from dried tea leaves into a solution of boiling water.

Liquid-Liquid Extraction

• A sample mixture is dissolved into two immiscible liquid phases (e.g., water and DCM).

• This is performed in a separator funnel to allow the denser liquid to settle at the bottom part.

• Components dissolve into the liquid where it has more affinity for.

Chromatography

Comes from the words“khromatos”=color and “graphia”=recording or description.

Chromatography

Separation technique applicable for gas, liquid, and other dissolved samples.

Degree of attractive interaction (affinity)

• The principle behind the different chromatographic methods

• Dissolved molecules to either the mobile phase or stationary phase used for the separation

silica gel

separation matrix

Stationary Phase

• Layer or coating on the supporting medium (column or planar surface) which interacts with the analytes

• Can either be solid or liquid

Mobile Phase

• Part of the chromatographic system that carries the solutes across the stationary phase.

• Can be liquid or gas

Normal Phase

• Stationary Phase; Polar

• Mobile Phase; Non-polar

Reverse Phase

• Stationary Phase; Non- polar

• Mobile Phase; Polar

Ascending

Movement is upward via capillary action of the solvent system.

Descending

Movement is downward due to the gravitational pull on the solvent system.

Isocratic

Mobile phase has a constant concentration.

Gradient

Mobile phase has a varying concentration

Planar

The stationary phase of the process take place on a plane (e.g., paper and TLC)

Column

The stationary phase takes place inside a tube like a packed column filled with the entire substance.

Partition

Particles are separated between liquid mobile and stationary phases (e.g., paper chromatography)

Absorption

Involves the separation of the components in a mixture based on the interaction of the adsorbate with the adsorbent

Paper Chromatography

A technique used for the separation of compounds based on the differential solubility in the stationary phase and mobile phase (solvent).

Stationary phase

water in the cellulose support (paper)— polar

Mobile phase

uses different liquid solvents— non-polar

Separation of components

It is based on their affinity between stationary and mobile phases.

farthest from origin

Less polar

closest from origin

More polar

Retention factor (Rf)

Used to quantify the affinity of a substance to the mobile phase. Rf values range from 0 to 1

Column Chromatography

A technique used for the separation of compounds based on the differential partitioning between stationary phase and mobile phase (solvent)

eluted first

Least Polar

eluted last

Most polar

Elute

the process of removing, extracting, or washing the molecule from the stationary phase

Eluent

refers to the mobile phase that is used to elute the different components from a sample substance.

Eluate

refers to the molecules or substances eluted together with the eluent and is collected at the end of the column

Thin-Layer Chromatography

a chromatographic technique used to separate the components of a mixture using a thin stationary phase supported by an inert backing.

farthest from origin, ↑Rf

Less polar

closest from origin, ↓Rf

More polar

Recrystallization

involves dissolving the solid in an appropriate solvent at an elevated temperature and allowing the crystals to re-form on cooling, so that any impurities remain in solution

Sublimation

involves melting the solid in the absence of solvent and then allowing the crystals to re-form so that impurities are left in the melt.

Alkaloids

• naturally occurring secondary metabolite.

• N-containing, weakly polar (hydrophobic) and would have higher affinity towards the organic phase (non-polar) of a liquid-liquid extraction.

• Nicotine, Caffeine, Morphine

Methylxanthines

• group of alkaloid compounds which are purine nucleotide metabolites.

• Caffeine, theophylline, and theobromine are common examples found in tea