Chromatography | Chemistry for Grade 11 (IGCSE) PDF Download

Paper Chromatography

• This technique, known as paper chromatography, is employed for separating substances based on their differing solubilities in a specific solvent. For instance, it can be used to separate different colored inks mixed to create black ink.
• To initiate the process, a line is drawn using a pencil on chromatography paper, and small spots of the sample are carefully placed on this line. Pencil is preferred for this step to prevent the ink from blending with the samples during the chromatography process.
• Subsequently, the paper is immersed into a solvent container, ensuring that the pencil line remains above the solvent level to prevent the samples from dissolving into the solvent.
• Through capillary action, the solvent ascends the paper, carrying some of the colored components along with it.
• As different substances exhibit varying solubilities, they travel at different rates, leading to their separation on the paper. Substances with higher solubility move a greater distance than those with lower solubility.
• This method effectively reveals the distinct constituents present in the ink or dye mixture.
• Analysis of the composition of ink using paper chromatography:
  

Interpret Simple Chromatograms

• When multiple substances are identical, they will generate chromatograms that are indistinguishable. 
• Incorporating a recognized compound as a reference point is customary, aiding in the identification of unknown spots. 
• Mixtures will segregate on the paper, revealing individual components as distinct spots. 
• Impurities will manifest with multiple spots, whereas pure substances should exhibit only one spot.