Gas Chromatography and HPLC


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  • The temperature inside the column depends on the boiling point of the sample.A common column arrangement is the ‘packed column’ in which the column contains a finely divided, inert, solid support.
  • The process can still be carried out if the compounds being separated are colourless, but you need to have some means of tracking them.
  • Of the two, reversed phase HPLC is more common
  • Gas Chromatography and HPLC

    1. 1. By: Avipsita, Sid and Momina
    2. 2. IntroductionGas ChromatographyHigh Performance LiquidChromatography (HPLC)
    3. 3. Click for more>>> Gas Chromatography Results Injector Port Detector Column Carrier Gas Simply Put Back to Introduction
    4. 4. The process of gas chromatography involves the injection of tiny amount of the sample into the head of a chromatography column, usually done by use of a micro syringe. Back to Introduction
    5. 5. Back toIntroduction
    6. 6. The column contains liquid, which is in stationary phase- this liquid is absorbed onto the surface of a inert solid.The different components of the sample separate as it passes through the column because they move at different rates.Simple Analogy: “Think of a swarm of bees and wasps moving over a field offlowers. The bees would tend to stop to pick up nectar from the flowers, butthe wasps would not. Therefore, at the other side of the field the waspswould be detected first, and then the bees.” Back to Introduction
    7. 7. There are many types of detector that can be used but they all identify the separate substances leaving the column.Different detectors have different ranges of selectivity:1. A non selective detector- responds to all compounds except the carrier gas2. A selective detector- responds to a range of compounds with a common physical or chemical property3. A specific detector – responds to a single chemical compound.4. Flame ionisation detector Back to Introduction
    8. 8. Back toWhy use this type of method? Introduction
    9. 9. Why use that type of method? Back to Introduction
    10. 10. Results Back to Introduction
    11. 11. High Performance Liquid Chromatography (HPLC)Check this out: So what is HPLC? Back to Introduction
    12. 12. HLPC is basically highly improved form of column chromatography.Instead of the solvent being allowed to drip through a column under gravity, itis forced through high pressure; making the process much faster. A very smallparticle size for the column packing material is used. This gives greater surfacearea for the interactions between stationary phase and the molecules flowingpast; allowing better separation of the components. There are two types: Back to Introduction
    13. 13. The two types of HPLC: Back to Introduction
    14. 14. Column is filled with silica particles and the solvent is non-polar. So polar molecules passing through the column will stick for longer to the polar silica than the non polar molecules. This means that the non-polar ones will pass through the column more quickly. Back to Introduction
    15. 15. - In this process the silica is modified to make it non polar by attaching a long hydrocarbon chain to its surface.- A polar solvent, for example a mixture of water and ethanol, is used.- This means that there will be a strong attraction between the polar molecules in the test sample. The attraction between the hydrocarbon chains attached to the silica (stationary phase) and the polar molecules in the solution is very weak. Polar molecules spend most of their time moving with the solvent; meaning that the polar molecules will travel through the column more quickly. What is Retention Time? Back to Introduction
    16. 16. Different compounds have different times as retention times depend on:• The pressure used-as it affects the rate of flow• The nature of the stationary phase- what the material is and how big theparticles are• The exact composition of the solvent• The temperature of the column Identifying Substances Back to Introduction
    17. 17. There are many ways to identify the substance which is passedthrough the columnFor example: UV absorption is one way as many organic compounds absorb UV light of various wavelengths. The amount of light absorbed will depend on theamount of a particular compound that is passing through the light beam at a time. Back to Introduction