max wavelength of the mixed dyes was found to be 400.00 nm with an absorbance of 0.203. To determine the concentrations of each dye individually, we tested standard solutions of each at the mixed solutions max wavelength and graphically determined the extinction coefficient to be .042 for FD&C Yellow 5 and .0186 for FD&C Red 4. By applying the determined extinction coefficient with the absorption of the unknown to Beer’s Law, the dye concentration of Gatorade was found to be 3.8 ppm for FD&C Yellow 5 and .32 ppm for FD&C Red 40. The concentrations of FD&C dye in our unknown was determined in a similar fashion. Using standard solutions of FD&C Yellow 6 and Red 3, we determined the max wavelength to equal 480.50 nm and 529.52 nm, respectively. At these wavelengths, the unknown solution showed an absorption of .151 for FD&C Yellow 6 and .327 for FD&C Red 3. We then cross referenced the absorption of each dye at these wavelengths and various concentrations to determine the extinction coefficient graphically. Assuming that the dyes do not absorb at the same wavelength, we used the extinction coefficient from the graphs which only measured absorbance from each dye at its own max wavelength. These coefficients were found to be .0429 for FD&C Yellow 6 and .0485 for FD&C Red
3. By entering these values into Beer’s Law and the max wavelength of the unknown mixture, which was .327 nm, we found FD&C Yellow 6 to have a .131 ppm concentration and FD&C Red 3 to have a 1.48.
- Spring '14
- pH, Food coloring, 3 g, Azo dyes, E number, Food colorings, fd&c yellow