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Ever wondered why candies are different colors? Many candies contain colored dyes. Bags of M&Ms or Skittles contain candies of various colors. Colors in candies are synthetic dyes that have been approved by the Food and Drug Administration (FDA). Sometimes the colors are mixtures of several dyes. The labels tell us the names of the dyes used in the candies. But which dyes are used in which candies? We can answer this by dissolving the dyes out of the candies and separating them using a method called chromatography.
The topic I chose to do my research paper on candy chromatography. In this experiment we will use candy chromatography to separate the different dyes in the Skittles. By doing this, this will determine which dyes make which color in the outer coating on the Skittles.
Candy chromatography is used to analyze FD and C dyes used in candy and food coloring. Also candy chromatography can be used to separate (purify) specific components from a complex mixture, based on a molecular size or other chemical properties and is used to identify chemicals. Highly accurate chromatographic methods are used for process monitoring. It is in this experiment we will find the FD and C dyes using paper chromatography. Chromatography is a technique used to separate the various components in a complex mixture solution. (Olsen, 2007 p. 1) Candy chromatography works by the components in the dye stick to each other and other substances.
Scientists use chromatography to analyze or examine a mixture, its components, and their relations to one another. Also to identify or determine the identity of a mixture or components based on known components. They use it to purify and separate components in order to isolate one of interest for further study. Scientists also use chromatography to quantify and determine the amount of the mixture and the components present in the sample.
Some everyday uses for chromatography are at a pharmaceutical company it's used to determine each chemical found in new product. At a hospital chromatography is used to determine alcohol levels in a patient's blood stream. In law enforcement it's used to compare a sample found at a crime scene to samples from suspects. In an environmental agency chromatography is used to determine the level of pollutants in the water supply. In a manufacturing plant chromatography is used to purify a chemical needed to make a product.
Paper chromatography has two phases a stationary phase and a mobile phase. The mobile phase flows through the stationary phase and carries the components of the mixture with it. (Clark, 2007 p.1) The paper is the stationary phase, and water is the mobile phase.
The principles of paper chromatography include capillary action which is the movement of liquid within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension. The liquid is able to move up the filter paper because its attraction to itself is stronger than the force of gravity. Another principle is solubility which is the degree to which a material dissolves into a solvent. Solutes dissolve into solvents that have similar properties. This allows different solutes to be separated by different combinations of solvents. The separation of components depends on both their solubility in the mobile phase and their differential affinity to the mobile phase and the stationary phase.
In 1903 Mikhail Tswett discovered chromatography he produced a colorful separation of plant pigments through a column of calcium carbonate. Chromatography became developed substantially as a result of the work of Archer John Porter Martin and Richard Laurence Millington Synge during the 1940s and 1950s. They established the principles and basic techniques of partition chromatography, and their work encouraged the rapid development of several types of chromatography method: paper chromatography, gas chromatography, and what would become known as high performance liquid chromatography. Since then, the technology has advanced rapidly. Researchers found that the main principles of Tsvet's chromatography could be applied in many different ways, resulting in the different varieties of chromatography described below. Simultaneously, advances continually improved the technical performance of chromatography, allowing the separation of increasingly similar molecules.
Scientists discovered that a strip of porous (full of small holes) filter paper could substitute for the column of absorbing powder. (Chromatography, p. 2) A drop of the mixture that was going to be separated was placed on the paper, and then one edge of the paper is dipped into the solvent. The solvent then spreads across the paper when this happens the mixture's components are carried with it. In paper chromatography the distance traveled by the component is the retention factor of the sample. The Rf value is the ratio between how far the component travels and the distance the solvent travels from a common starting point (the origin).
After the components have finished spreading across the paper, the paper needs to be dried and sprayed with reagent that changes the color of the component.
Some of the pigments dissolve quicker than others, which causes them to move up the paper through capillary action into different areas. This separation allows the different pigments to be identified while on the paper through color identification.
Because molecules in ink and other mixtures have different characteristics (such as size and solubility), they travel at different speeds when pulled along a piece of paper by a solvent (in this case, water). For example, black ink contains several colors. When the water flows through a word written in black, the molecules of each one of the colors behave differently, resulting in a sort of "rainbow" effect.
Many common inks are water soluble and spread apart into the component dyes using water as a solvent. Components move at different speeds, so they will show up separated spots. These will need to be cut out and analyzed further.
Candy chromatography is what we will use in our experiment to determine what really makes those colors in Skittles.