Chemistry (Chromatography)

• Chromatography is a process of separating the components of components mixture according to their differences in partition coefficient on a stationary phase.
• it requires a mobile phase that consist of the solute components of the mixture and the solvent called an eluent, and a stationary which is an adsorbent that has intermolecular affinity not only for the eluent but also for the solute components of the mixture.
• since its conception in 1900 by Mikhail Tsvet, chromatography has become an important analytical tool and separation technique for mixtures.
• two basic types of chromatography exist. One is column chromatography, where the stationary phase if held in a narrow tube, and the mobile phase is forced through the tube under driving forces such as gravity or fluid pressure.
• The features of chromatography involving separation and the inherent affinity of the components to the process makes it a useful tool in determining, isolating, and identifying components of a mixture.
• gas chromatography is the premier chemical separation method fro volatile compounds.
• high performance liquid chromatography is a modern application of liquid chromatography that utilize different types of stationary phases, a pump that moves the mobile phase and analyte through the column,
• as the mobile phase over the stationary phase, the chromatogram develops.
• the leading edge of the mobile phase in the chromatogram is called solvent front.
• paper chromatography make use of the polar cellulose molecules in the paper as the stationary phase.
• since paper is self supporting adsorbent, it does not requiere much preparation. A chromatographic paper, manufactured from highly purified cellulose with close control over porosity and thickness, is spotted with a mixture and is then placed in contact with the eluent to form the mobile phase.
• thin-layer chromatography is of the most popular solid- liquid chromatography varients and is used for identifying compounds and determining their purity.
• the stationary phase is typically alumina or silica gel, commonly prepared by triturating the material and mounting a thin or film onto plate
• Another type of chromatography is planar chromatography, where the stationary phase is supported on a flat plate or in the pores of a paper, and the mobiles phase moves through the stationary phase by capillary action or under the influence of gravity
• two types of chromatography, the column chromatography and the planar chromatography
• what is solvent front?


  leading edge of the mobile phase in the chromatogram
• 2 common stationary phase in TLC are the normal pahse and reverse pahse. in normal phase chromatography, the staionary is more polar than the mobile phase; in reverse phase , the stationary phase is less polar than the mobile phase.
• whar the typical stationary phase

  alumina and silica gel
• 3 types of visualization that can be used: destructive, nondestructive and semi-distructive
• what are the types of visualization that can be used

  destructive, nondestructive, and semi-destructive
• destructive visualization destroys the compounds, but spots will be shown.
• Nondestructive visualization uses a wavelength of radiatoin that enable the spots to be seen more clearly than with visible light.
• Semi-destructive visualization uses iodine vapors that will absorb onto the spots which colors them.
• in identifying products that are in a mixture, the retention factor is often used which is a ratio of the distance travelled by the component to the distance travelled by the solvent.
• retention factor is useful in comparing the results of one chromatogram to the result of another. if the condition in which the chromatogram are run remain unchange, the retention factor fro a given material should remain constant.if the retention factor of unknown does not match that of a known material, they are not the same compound.