Introduction
Many people do not know that food dyes can potentially be damaging to the body. The dyes used in this experiment Red #40, Yellow #5, and Yellow #6, are actually found to be tainted with contaminants (Curran). These dyes, which are found in common food products, were tested for. Red #40, the most-widely used dye, causes hypersensitivity (allergy-like) reactions in a small number of consumers and might trigger hyperactivity in children (Jacobson and Kobylewski). Yellow #5 may be contaminated with several cancer-causing chemicals. Also, it may cause sometimes-severe hypersensitivity reactions in a small number of people and might trigger hyperactivity and other behavioral effects in children (Jacobson and Kobylewski). Yellow #6 may also be contaminated with cancer-causing chemicals and occasionally causes severe hypersensitivity reactions. Yellow #6 adds an unnecessary risk to the food supply (Jacobson and Kobylewski).
In this experiment, spectrophotometry was utilized as an essential tool. Spectrophotometry and UV-Visible radiation can be used in combination to determine concentrations of food dyes. Food dyes absorb electromagnetic radiation in the visible spectrum (Sandi-Urena et al). In this experiment, the interaction of UV-Visible radiation and organic molecules in commercial food products were studied to determine concentration of certain food dyes. From the given variety of dye colors, Red #40, Yellow #6, and Yellow #5 were compared using an OceanOptics spectrophotometer. In combination with the use of spectrophotometry, Beer’s Law was important in this experiment as well. Beer’s Law is described as A=ɛbc where A is absorbance, ɛ is the molar absorptivity that is, the path length of the cuvette in which the sample is contained, and c is the concentration of the compound in solution (Blaunch). The main goal of this lab was to find the unknown concentration of commercial food products containing Red #40, Yellow #6, and Yellow #5.
Methods
Preparation of Stock Solution First, the solution of Red #40 was prepared. 0.02 g of the solid dye was obtained and mixed with 100 mL of Deionized water in a 150 mL beaker. The same amounts and procedures were followed for Yellow #6 and Yellow #5. In order to determine which solution was to be used as the stock, the absorbance was observed in a Spectrophotometer. If the absorbance was over 1, the solution needed to be diluted until it reached an appropriate level of absorbance. After setting up the spectrophotometer, separate cuvettes were prepared. One was filled with just deionized water to be used as a blank when changing wavelengths. The other cuvettes were filled with each according dye solution. For the dye solutions, they were diluted using serial dilution. 10 mL of the original solution was taken and combined with 10 mL of deionized water. The solution was continuously diluted until the absorbance was at or below 1, which would then be the stock solution. The same procedure was performed on each dye until a stock solution was found.
Creating a Calibration Curve After the stock solutions had been prepared, a calibration curve was created using 5 points. First, the maximum absorbance of each solution was needed to be found. Using the stock solution of the specified dye, serial dilution was performed by taking 10 mL of the stock (Solution 1) in combination with 10 mL of deionized water. This new solution (Solution 2) would then be similarly tested in the spectrophotometer to find the maximum absorbance. 10 mL of Solution 2 was then added with 10 mL of deionized water to make Solution 3. The procedures were repeated using serial dilution until there were 5 solutions. Each solution was then tested for maximum absorbance and recorded. When the Red #40 solution was put in the spectrophotometer, the absorbance read high above 1. In order to bring it closer to 1, it was diluted 3 times. Once the readings had fallen below one, that solution was used as the stock.
