Chromotography Flashcards
Chromotography
Chromotography is an analytical technique that separates components of a mixture. The sample is carried through a medium called the stationary phase (solid material) by a solvent called the mobile phase (a solid). It is a technique for separating components of a mixture by passing it through a medium in which each component moves at a different rate.
The different components of the mixture will travel through the stationary phase at different rates, allowing them to be separated. The different types of chromatography are characterized by type of station phase.
During chromatography, the molecules will experience interactions with both the mobile phase and stationary phase. The speed with which the molecules move over the stationary phase depends on the relative strength of these interactions.
Planar Chromotography
Planar chromatography is a separation technique in which the stationary phase is a flat plane. The stationary phase can be paper (paper chromatography) or a layer of solid particles spread on a support. Different mobile phases can be used in each to fine tune relative interactions of the components with the mobile phase and stationary phase.
Mobile Phase and Stationary Phase
Mobile phase is the solvent or gas that carries the sample over the stationary phase. The sample is dissolved into a solution, and the solution helps move it up the stationary phase.
The phase that the components of the mobile phase absorb onto is the stationary phase.
Molecular Interactions
Molecules in the mixture that have a strong affinity (degree which a substance combines with another) for the stationary phase and a low affinity for the mobile phase will be adsorbed onto the surface of the stationary phase - and therefore will travel slowly over the stationary phase. Molecules with low affinity for the stationary phase and a high affinity for the mobile phase will travel more quickly over the stationary phase. This provides information about polarity of the mobile and stationary phase and solvent.
Retention factor
Retention factor is the ratio of the height of a component reaches to the height of the solvent front.
Height of component/height of solvent front.
Paper Chromotography
In paper chromatography, a stationary phase of paper is used.
Thin Layer Chromotography
TLC is used for detecting the number of components in a micture, and therefore its purity. The stationary phase is a thin layer of absorbent on glass, plastic.
Gas Chromotagraphy
Gas chromatography is a form of chromatography because the stationary phases is contained inside a tube, called the column. It is used to analyse volatile substances in the gas phase. The components of the sample are dissolved in a solvent and vapourised. The mobile phase is an inert gas that carries the sample through the heated column stationary phase. In GC, the sample does not interact with the mobile phase, so movement is only determined by interactions with the stationary phase.
