The modern spectrophotometer is not actually based on Coleman Instruments' design, but rather on one by Arnold Beckman.1,2 He developed a mechanism to accurately control wavelength selection from a quartz prism, and integrated the optics and electronics of his spectrophotometer into a single unit that greatly simplified its use. Beckman's Model DU spectrophotometer was introduced in 1942, and its production had an immediate impact not only on scientific research,2 but also on the war effort. The DU spectrophotometer was extensively used in the mass production of penicillin.1 Scientists also employed the device in the analysis of crude oil, which contains benzene--used to make synthetic rubber--and toluene, a starting material for trinitrotoluene (TNT).1
In 1913, Bohr described the fundamental physical principles on which spectrophotometers are built. He proposed that atoms exist in only a limited number of energy levels, which represent the energy states of electrons in an atom. When one ...
