Chromatography Stationary Phase Essay

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Chromatography
Introduction
Chromatography is the separation of mixtures into their components as a result of differential distribution of the solutes in order for identification, analyses, purify and/or quantity of the mixture for a mobile medium and for a stationary absorbing medium. Examples of when chromatography is used are in pharmaceutical companies in order to find out the amount of chemicals used in each new product, hospitals for detection of sugar/blood levels and law enforcement for comparisons of samples found at a crime scene. Chromatography is identified by their colour and Rf number. The Rf number calculation is:

Illustration of chromatography

There are many different types of chromatography, such as:
Paper Chromatography
Stationary phase: Paper
Mobile phase: Organic or aqueous solvent
Paper chromatography is when it separates liquid samples with a liquid solvent and a paper strip. The paper is put into a container containing a small amount of the solvent in it, which is below the line with the spots with the top of the container covered. This is used to identify organic and inorganic compounds and is used in crime scene investigation.
Thin-Layer Chromatography
Stationary phase: Silica gel supported on plastic, metal film
Mobile phase: Organic or aqueous solvent
Separation of dried liquid samples with a liquid solvent and a glass plate covered with a thin layer of silica gel. The thin layer chromatography plate is out into a beaker containing the solvent but making sure that the solvent is below the pencil line. Thin-layer chromatography is used to detect pesticides or insecticide in food.

Gas Chromatography
This involves a sample being vaporised and injected onto the head chromatographic column. The sample is transported through the column by the flow of inert, gaseous mobile phase. The column itself contains a liquid stationary phase which is absorbed onto the surface of an inert solid. Examples of application in the real world of gas chromatography being used would be drug testing, testing for fibre, crime scenes and to detect residual from explosives

Liquid Chromatography
Stationary phase: Solid beads
Mobile phase: Organic or aqueous solvent
This separates liquid samples with a liquid solvent and a column composed of solid beads. This is used to test water pollution and can be used to analyse metal ions and organic compounds in solutions.
High Performance Liquid Chromatography
This does not allow the solvent to drip through the column due to gravity as the solvent is forced through under high pressures. This technique allows you to use smaller particle size for the column packing material allowing a much better separation of the components of the mixture. Factors affecting the retention time are length of column, packing material, type of solvent and flow rate of solvent.
Infrared Spectroscopy
Infrared spectroscopy is the study of the properties of material systems by means on their interaction with infrared radiation; ordinarily the radiation is dispersed into a spectrum after passing through the material (Answers). This is acquired on a special instrument called an IR spectrometer. Using this allows us to gather information about the compounds structure and its purity. IR can be used in industries such as:
Forensic Analysis
Crime Investigation
Chemical Analysis
Chemistry Applications
The infrared radiation is part of the electromagnetic spectrum, which is between the visible and microwave region. The radiation emitted is absorbed by organic molecules and converted into energy of molecular vibration. Certain functional groups strongly absorb the infrared radiation allowing us to identify the number present of a functional group. The infrared spectra plots the wavelength and transmittance percentage and in order to identify the functional group is by a deep dip in the line, which you then draw a vertical line from the bottom of the dip and read off the
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