• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Comparing High Pressure Liquid Chromatography and Gas Chromatography

Extracts from this document...


´╗┐Comparing High Pressure Liquid Chromatography and Gas Chromatography HPLC and GC have different approaches to separating components in mixtures. HPLC deals with separating particularly non-volatile and liquid substances such as ions, polymers and other complex structured molecules into their components; whereas, GC deals with volatile and gaseous substances or the substances could be vaporised (organic or inorganic molecules such as alcohols) while they are in the injection unit. In HPLC high pressures are given from a pump in order to force the mobile phase through the column and interact with the components within the mixture. This is because compounds that react very slowly due to their complex structure are being separated within the column. ...read more.


Heat is being used instead in GC to turn the mixture into gas form in order for the gaseous mobile phase to carry it along the column; the temperature can be controlled by a thermostatically controlled oven; the HPLC is done at room temperature conditions. Also in GC the mobile phase is a gas such as nitrogen or helium; in HPLC, the mobile phase is in a liquid state and is usually polar such as the mixture of water and methanol. UV light is absorbed by components after they are separated from the mixture in HPLC and the amount of light they absorb is detected by sensors in the UV Light Spectrometer. ...read more.


It helps to identify them. Some other common HPLC detectors are conductivity detectors, fluorescence detector and evaporative light detectors. A special detector used in GC is the flame ionization detector. This detector senses the individual components in the mixture as it uses hydrogen gas that burns in air. In GC, the separation of the components in the mixture typically depends on how volatile they are, the most volatile component leaves the column first. Whereas, in HPLC polarity affects the separation of the components; usually non-polar stationary phases are used, and more polar mobile phases carry the more polar component out of the column and into the detector at a faster rate. The non-polar components will take more time to exit the column as they will spend more time attached to the non-polar stationary phase. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Physical Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Physical Chemistry essays

  1. Identification of amino acids by chromatography.

    and the distance moved by the solution (17cms), the mark should be observable at 7.3cms (1d.p.). On the chromatogram, I can see a yellow mark at 7.4cms, which is inaccurate by 0.1cms, but this is not disastrous. Discussion There are other methods of chromatography that I would be interested in investigating.

  2. Demonstrate an understanding of the theory, principles and practice of separation of liquid mixtures ...

    heated, the vapour pressure will not have the same composition as the liquid. Instead, the resulting vapour mainly consists of the more volatile of the two liquids, the one with the lower boiling point.

  1. Investigating the Rate of the Reaction between Bromide and Bromate Ions in Acid Solution

    course of the practical, so this could have led to a significant effect on the results before it was noticed. 4.4 Equipment Errors In this section I will quantitatively evaluate the margin of error in the equipment that I used.

  2. Investigating how concentration affects rate of reaction

    Now that I have proved the rate equation experimentally, I want to find a value for the constant, 'k'. This is called the rate constant (1, page 229) and its value changes with temperature. Using my results at a certain temperature I should be able to calculate a value for 'k'.

  1. High Pressure Liquid Chromatography procedure steps

    (Fundamentals of HPLC - Agilent Technologies PDF Manual Download - Free User Manual Guide, no date) 1. A pump is used to force a liquid mobile phase from the solvent reservoir attached to the system, to flow through the liquid chromatograph.

  2. Column chromatography is a larger scale of thin layer chromatography.

    water-ethanol mobile phase and will run through the column at a faster rate. Optimum separation is referred to the best separation possible of the compounds in the mixtures of substances under the current conditions; the peaks of the compounds in the mixture have no interference with

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work