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Separation of mixtures by paper chromatography


This method is often used in the food industry. It is used to identify chemicals (coloring agents)
in foods or inks. For example, if a scientist wants to know how many substances are in a
particular blob of ink, paper chromatography can be used.

Below is an illustration of using chromatography to separate and identify the different
chemicals in an ink (mixture)

chromatography

A blob of ink is smeared on a special paper called filter paper. The paper is placed in a trough
of solvent. The solvent used depends on the chemicals in the ink blob. As the paper gets
soaked upwards, it attracts the various chemicals in the ink blob. Because different chemicals
have different rates of attractions to the solvent, the chemicals will travel upwards in different
amounts. Sometimes, a chemical may not react at all. If a different solvent is used, all the
various chemicals may travel at a completely different rate.

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