Separation of a Dye Mixture Using Chromatography—Advanced Inquiry Laboratory Kit

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Big Idea 2, Investigation 5, Primary Learning Objective 2.10

The entire palette of artificial food colors is derived from just seven dyes certified by the FDA for use in food, drugs and cosmetics. How can these FD&C dyes be identified in a mixture? How do the molecular structures of the dye molecules influence their properties, relative solubility or affinity for different solvents?

The purpose of this advanced-inquiry lab is to investigate the factors that influence the separation of food dyes using paper chromatography. Students begin by comparing the separation or resolution of three FD&C dyes using two solvents. Reviewing the evidence provided by the cooperative class data leads students to select a solvent for further study. In the guided-inquiry section of the lab, students design an experiment to identify a solvent that will give maximum resolution of a mixture of dyes. The results may be applied to study the connection between the structure and mobility of the food dyes. An investigation into the composition of colored candy shells may be incorporated into optional extension activities.

The primary learning objectives for this advanced-inquiry lab focus on the effects of molecular structure on the nature and strength of intermolecular forces between molecules or ions. The lab also integrates key science practice skills for analyzing data to identify trends.

Complete for 24 students working in pairs.