In 1940, nearly 30 years after Danish physicist Neils Bohr explained how light energy affects the electrons orbiting atomic nuclei, Coleman Instruments produced an instrument to take advantage of this principle. The device was an attachment to the company's pH meter that could measure absorbance of light in the ultraviolet (UV) region.1 In the 61 years since, absorption spectroscopy has become one of the most widely used analytical techniques in scientific research. Investigators routinely employ this method to measure the concentration of nucleic acid and protein samples, and UV-visible spectrophotometers are considered standard equipment for molecular biology labs.

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....

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