- Is a technique used to separate and identify the components of a mixture.
- Works by allowing the molecules present in the mixture to distribute themselves between a stationary and a mobile medium.
- Molecules that spend most of their time in the mobile phase are carried along faster.
Chromatography
is a laboratory technique that separates components within a mixture by using the differential affinities of the components for a mobile medium and for a stationary adsorbing medium through which they pass.
Chromatography
showing a difference, distinctive
Differential
natural attraction or force between things
Affinity
gas or liquid that carries the components
Mobile Medium
the part of the apparatus that does not move with the sample (stationary phase)
Stationary Medium
examine a mixture, its components, and their relationship to one another
Analyze
determine the identity of a mixture or components based on known components
Identify
separate components in order to isolate one of interest for further study
Purify
determine the amount of the mixture and/or the components present in the sample
Quantify
- Because molecules in mixtures have different characteristics (such as size and solubility), they travel at different speeds when pulled along a piece of paper by a solvent (water).
- For example, black ink contains several colors. When the water flows through a word written in black, the molecules of each one of the colors behave differently, resulting in a sort of “rainbow” effect with the colors separating out at different rates.
RF (Retardation Factor)
Rf =
distance moved by substance / distance moved by solvent front
Types of Chromatography
- Paper Chromatography
- Thin- Layer Chromatography
- Gas Chromatography
- Liquid Chromatography
separates dried liquid samples with a liquid solvent (mobile phase) and a paper strip (stationary phase)
Paper chromatography
the movement of liquid within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension. The liquid is able to move up the filter paper because its attraction to itself is stronger than the force of gravity
Capillary Action
the degree to which a material (solute) dissolves into a solvent. Solutes dissolve into solvents that have similar properties. (Like dissolves like) This allows different solutes to be separated by different combinations of solvents.
Solubility
Separation of components depends on both their solubility in the mobile phase and their differential affinity to the mobile phase and the stationary phase.
Principles of Paper Chromatography
- uses an absorbent material on flat glass or plastic plates.
- It is used to detect pesticide or insecticide residues in food.
- is also used in forensics to analyze the dye composition of fibers.
- Most samples are not colored and need to be visualized with a UV lamp.
Thin Layer Chromatography
gas mixture, called the ?, composed of an inert “carrier” gas (usually Helium) and various other chemical components in the vapor phase introduced at the Injection Port pass through a non-moving material
Mobile Phase
- usually tightly packed into a copper tube called the Column…
- which separates the gas stream into its particular components based on how “quickly” they move through. The components reach a…
Stationary Phase
generates an electrical signal
Detector
- is used in airports to detect bombs and is used in forensics in many different ways.
- It is used to analyze fibers on a persons body and also analyze blood found at a crime scene.
- Helium is used to move a gaseous mixture through a column of absorbent material.
Gas Chromatography
- A sample mixture is passed through a column packed with solid particles which may or may not be coated with another liquid.
- With the proper solvents, packing conditions, some components in the sample will travel the column more slowly than others resulting in the desired separation.
- is used in the world to test water samples to look for pollution in lakes and rivers.
- is used to analyze metal ions and organic compounds in solutions.
- uses liquids which may incorporate insoluble molecules.
Liquid Chromatography
Liquid/Solid Chromatography
adsorption chromatography
