Students use Beer's Law and the technique of spectrometry to determine the amount of food dye present in powdered drink mixes.
Students first use spectrometry to acquire the spectra of three food dyes; FD&C Yellow 5, FD&C Red 40, and FD&C Blue 1. In doing so, they find the wavelength at which each absorbs a maximum amount of light. Next, they construct a standard calibration curve for each dye from a series of solutions of known concentrations. They can use the formula of this curve to quantitatively determine the amounts of these food dyes present in any other solution.