Thin Layer Chromatography and Column Chromatography
Introduction
Chromatography is a technique used to separate a mixture into its individual components. In this experiment, chromatography is done by using a thin layer chromatography (TLC) plate and filter paper. The word ‘chromatography’ itself means the separation of colours. However, nowadays, both coloured and colourless compound are used in chromatography by various methods.
In chromatography, the separation process of mixture is mainly based upon the polarity and molecular weight of sample. Then, the separation involves mobile phase and stationary phase. The mixture to be separated is applied to an immovable solid surface, which is the stationary phase, such as TLC plate and the filter paper. Then, suitable solvent is then added to ‘wash’ the porous solid by the flow of solvent, which is the mobile phase. The mobile phase can be liquid (in liquid chromatography) which is in this experiment, or gas (as in gas chromatography).
The porous solid, which is the stationary phase, adsorbs different substances depending on the polarity of the substance adsorbed to it. The term “adsorption” means the adhesion or stickyness of a substance to the surface of another substance. As mentioned, chromatography is based on polarity. So, a mixture of compound is separated or adsorbed differently on porous solid (stationary phase) based on the polarity of both the compound itself and also the stationary phase. By the concept of “like attracts like”, a polar stationary phase will adsorb a polar components more strongly than a non-polar component, which also indicates that a non-polar components will be removed along the solvent more easily and faster than the polar compounds. It is the same case as where a polar solvent is used. The polar component will be moved along the solvent more quickly and hence, leave behind the non-polar component which is move more slowly and removed later. The solvent (mobile phase) moves through the stationary phase (porous solid) by capillary
Chromatography is a technique used to separate a mixture into its individual components. In this experiment, chromatography is done by using a thin layer chromatography (TLC) plate and filter paper. The word ‘chromatography’ itself means the separation of colours. However, nowadays, both coloured and colourless compound are used in chromatography by various methods.
In chromatography, the separation process of mixture is mainly based upon the polarity and molecular weight of sample. Then, the separation involves mobile phase and stationary phase. The mixture to be separated is applied to an immovable solid surface, which is the stationary phase, such as TLC plate and the filter paper. Then, suitable solvent is then added to ‘wash’ the porous solid by the flow of solvent, which is the mobile phase. The mobile phase can be liquid (in liquid chromatography) which is in this experiment, or gas (as in gas chromatography).
The porous solid, which is the stationary phase, adsorbs different substances depending on the polarity of the substance adsorbed to it. The term “adsorption” means the adhesion or stickyness of a substance to the surface of another substance. As mentioned, chromatography is based on polarity. So, a mixture of compound is separated or adsorbed differently on porous solid (stationary phase) based on the polarity of both the compound itself and also the stationary phase. By the concept of “like attracts like”, a polar stationary phase will adsorb a polar components more strongly than a non-polar component, which also indicates that a non-polar components will be removed along the solvent more easily and faster than the polar compounds. It is the same case as where a polar solvent is used. The polar component will be moved along the solvent more quickly and hence, leave behind the non-polar component which is move more slowly and removed later. The solvent (mobile phase) moves through the stationary phase (porous solid) by capillary
References: Mohrig. (n.d.). Thin Layer Chromatography. Retrieved June 15, 2012, from Online Lab Manual Home: http://www.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Appendix/Techniques/TLC/thin_layer_chrom.html Thin Layer Chromatography. (n.d.). Retrieved June 15, 2012, from http://courses.chem.psu.edu/chem36/Experiments/PDF 's_for_techniques/TLC.pdf