Abstract
This report gives a detailed description of chromatography as in related to chemical lectures obtained from thinkingwell.com. The report is subdivided into subheadings to give detail descriptions of the method. The main method used is TLC
Introduction
Chromatography is a chemical method for separating assortments of coloured chemicals known as pigments. It is the most significant separation technique for bio molecules. The result of chromatography experimentation is a chromatogram. All chromatographic arrangements include a stationary phase, a mobile phase sample, and substrate.
How the Retention factor, Rf , value is determined
The retention factor, or Rf, is described as the distance travelled by the compound from origin divided by the distance travelled by the solvent from origin.
Rf= Distance travelled by the compound/ Distance travelled by solvent front
In the video, the distance covered by the blue dye was 55mm and red was 38mm while the solvent was 67mm. Therefore
Red RF=38/67 = 0.6
Blue RF=55/67 = 0.8
How to create a micropipette
The video illustrated a process where micropipette could be produced from disposable pipettes. Initially, the disposable pipette is heated in the flame of a Bunsen burner. The disposable pipette must be twisted back and forth to ensure uniform heating. When the glass is softened, the disposable pipette is removed from the flame and stretched apart. This produces a very thin tube of glass. After the tube cools, it is cut into numerous micropipettes.
The different types of chromatography
There are many types of chromatography techniques used all over the world. However, for the sake of the video three techniques are mentioned. They include Gas, HPLC, and TLC.
High Performance Liquid Chromatography (HPLC)
For this kind of chromatography, the parting of compounds is done based on their characteristic polarities. The interface of the compounds with the stationary phase of the column is also measured. The gears necessary for include a pump, a stationary phase, and a detector. The Retention time varies with the strength of interactions.
Thin Layer Chromatography
In this type of chromatography, the stationary phase is made up of a thin layer of porous, covered on an innate plate of glass, metal or plastic. Dependant on the procedure of TLC, the width of the porous layer varies.
The example of separating the pigments in grape drink
The distance moved by a pigment of grape drink is the distance from the baseline, where the pigment was applied, to the centre of the pigment smear at the end of the chromatography. In this demonstration, the red pigment moved 38 mm, while the blue pigment moved55 mm. Rf values are calculated by dividing the distance the sample moved by the distance the solvent front moved. Rf values of components of a mixture can be compared to known Rf values to identify components. For example, if a particular blue pigment has a known Rf of 55 mm / 67 mm = 0.82, the blue pigment of grape drink could be identified as that pigment.
The separation in TLC is based on differences in polarities. Water is a polar molecule, while the molecules making up the filter paper are non-polar. The blue pigment is more polar than the red pigment, and thus is more soluble in water than on the surface of the filter paper. Therefore, the blue pigment travels further.
Q/A
Chromatography
Chromatography is a group of procedures for separating components of a mixture.
Mobile phase, stationary phase
The stationary phase is the support on which the chromatography is performed. For example, filter paper is a stationary phase used in TLC.
The mobile phase is the moving solvent front, which carries the mixture. For example, water is a mobile phase used in TLC.
Retention factor
The retention factor, or Rf, is described as the distance travelled by the compound from origin divided by the distance travelled by the solvent from origin.
Chromatogram
The result of chromatography experimentation is a chromatogram
References
www.thinkingwell.com
