ultraviolet-visible spectroscopy
The Beckman DU 500 Spectrophotometers used in the ICN project scans light in the ultraviolet (UV) and visible (vis) spectrum. A chemical solution in a small container called a cuvette is exposed to ultraviolet (UV) and visible (vis) light from 200 to 800 nm. A detector measures the amount of light transmitted or absorbed by the solution. The UV-vis spectrophotometer records the absorbance for each wavelength and plots the data as a spectra like the one pictured below. The UV-vis spectra can be used to confirm the identity of a compound or to determine the concentration of a solution.
Absorbance vs.Wavelength (nm) for green food coloring