Method Method


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Chromatography is a separation technique in which a mobile phase (water, ethanol) carrying a mixture moves in contact with a selectively absorbent (paper, alumna, silica gel) stationary phase.

  • Chromatography is a separation technique in which a mobile phase (water, ethanol) carrying a mixture moves in contact with a selectively absorbent (paper, alumna, silica gel) stationary phase.



Method

  • Method

  • a) A small amount of the mixture to be separated is placed on a strip of chromatography paper.

  • b) The end of the paper is placed in a suitable solvent.

  • c) The solvent soaks up through the paper and dissolves the sample of material being analysed. Each of the components of the mixture dissolves to a certain extent. The least soluble come out of solution and appear as a spot on the paper.

  • d) Thus the original sample will be split into its various component sat different intervals along the paper.

  • Note: Avoid handling the paper as oils from the hands can affect the result.



Stationary Phase -Thin layer of aluminium oxide or silica gel on a glass plate or aluminium foil.

  • Stationary Phase -Thin layer of aluminium oxide or silica gel on a glass plate or aluminium foil.

  • Method

  • A spot of the mixture been analysed is placed near the bottom of the plate. When the spot is dried the TLC plate is placed standing in a suitable solvent.

  • TLC is more efficient than paper in that the particles in the stationary phase are smaller and this gives better separation of components in the mixture.

  • Uses of TLC

  • Pharmaceutical industry - to determine the purity of drugs.

  • Forensic science-To separate the colours in dyes extracted from a crime scene.

  • Analysis of drugs like cannabis





Stationary Phase-made into slurry using an appropriate solvent.

  • Stationary Phase-made into slurry using an appropriate solvent.

  • The mixture to be separated is dissolved in a solvent and added to the top

  • of the column.

  • The solvent is allowed to pass through the column and is kept moist. If the

  • column is long a series of coloured bands will appear along the column.

  • This series of bands is called column chromatography.

  • The procedure of passing a solvent through the column is called elution.

  • The general term for the solvent is the eluent.





Mobile Phase=Inearth Gas(Argon, Nitrogen,Helium))

  • Mobile Phase=Inearth Gas(Argon, Nitrogen,Helium))

  • Stationary Phase= a high Boiling Point liquid spread on solid

  • particles(alumina)that are packed into a long coiled tube called the column. This

  • coiled tube of small diameter and several meters in length is kept inside a

  • temperature controlled oven.

  • Method

  • a) The sample is injected, vaporised, and carried through the tube using an inert gas like Helium, Nitrogen, or Argon.

  • b) The various components in the mixture separate as they flow through the column.

  • c) As each component leaves the column, it passes a detector which records a signal.



Uses

  • Uses

  • Level of alcohol in blood or Urine.

  • Drug test athletes

  • GC-MS. Gas Chromatography + Mass Spectrometry.

  • Each individual component analysed.

  • Analyse performance of drugs in body

  • Detect gases from waste dumps and organic pollutants in water.



The substance to be analysed is added to a liquid solvent and passed over a solid.

  • The substance to be analysed is added to a liquid solvent and passed over a solid.

  • Better separation if the particles in the stationary phase are very small. A pump is used, therefore the column need not be as long as in Gas Chromatography. Another advantage is that HPLC is carried out at a lower temperature and can analyse compounds that would decompose at a higher temperature.



Used



Mass Spectrometry (Francis William Aston)

  • Mass Spectrometry (Francis William Aston)

  • - built to measure the masses of atoms.

  • - Detect the presence of Isotopes.

  • A Mass Spectrometer is used to

  • Identify the presence of Isotopes

  • Measure the relative abundance of isotopes

  • Measure relative atomic masses and relative molecular masses

  • Identify unknown compounds.



How a spectrometer works.

  • How a spectrometer works.

  • 1. Vaporisation

  • 2. Ionisation

  • 3. Acceleration

  • 4. Separation

  • 5. Detection

  • Uses of a Mass Spectroscope

  • Used in conjunction with Gas Chromatography to detect banned drugs in athletes.

  • Test for drugs taken by drug addicts

  • Analyse the gases in the tail of a comet.



Used to detect the presence of certain functional

  • Used to detect the presence of certain functional

  • groups in molecules.

  • Also used to detect or measure the concentration of organic compounds in solution.

  • Measure the amount of drug metabolite reaching a

  • certain part of then body.




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