---
title: "DU spectrophotometer"
chunk: 4/5
source: "https://en.wikipedia.org/wiki/DU_spectrophotometer"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:41:22.285535+00:00"
instance: "kb-cron"
---

The Beckman spectrophotometer was the first easy-to-use single instrument containing both the optical and electronic components needed for ultraviolet-absorption spectrophotometry within a single housing. The user could insert a cell tray with standard and sample cells, dial up the desired wavelength of light, confirm that the instrument was properly set by measuring the standard, and then measure the amount of absorption of the sample, reading the frequency from a simple meter. A series of readings at different wavelengths could be taken without disturbing the sample. The DU spectrophotometer's manual scanning method was extremely fast, reducing analysis times from weeks or hours to minutes.

It was accurate in both the visible and ultraviolet ranges. 
Working in both the ultraviolet and the visible regions of the spectrum, the model DU produced accurate absorption spectra which could be obtained with relative ease and accurately replicated. The National Bureau of Standards ran tests to certify that the DU's results were accurate and repeatable and recommended its use.
Other advantages included its high resolution and the minimization of stray light in the ultraviolet region. Although it was not cheap, its initial price of $723 made it available to the average laboratory. In comparison, in 1943, the GE Hardy Spectrophotometer cost $6,400. Practical and reliable, the DU rapidly established itself as a standard for laboratory equipment.

== Impact ==

Credited with having "brought about a breakthrough in optical spectroscopy", the Beckman DU has been identified as "an indispensable tool for chemistry" and "the Model T of laboratory instruments". Approximately 30,000 DU spectrophotometers were manufactured and sold between 1941 and 1976.
The DU enabled researchers to perform easier analysis of substances by quickly taking measurements at more than one wavelength to produce an absorption spectrum describing the complete substance. For example, the standard method of analysis of the vitamin A content of shark liver oil, before the introduction of the DU spectrophotometer, involved feeding the oil to rats for 21 days, then cutting off the rats' tails and examining their bone structure. With the DU's UV technology, vitamin A content of shark liver oil could be determined directly in a matter of minutes.
The Scripps Research Institute and the Massachusetts Institute of Technology credit the DU with improving both accuracy and speed of chemical analysis. MIT states: "This device forever simplified and streamlined chemical analysis, by allowing researchers to perform a 99.9% accurate quantitative measurement of a substance within minutes, as opposed to the weeks required previously for results of only 25% accuracy."
Inorganic chemist and philosopher of science Theodore L. Brown states that it "revolutionized the measurement of light signals from samples". Nobel laureate Bruce Merrifield is quoted as calling the DU spectrophotometer "probably the most important instrument ever developed towards the advancement of bioscience." Historian of science Peter J. T. Morris identifies the introduction of the DU and other scientific instruments in the 1940s as the beginning of a Kuhnian revolution. 
For the Beckman company, the DU was one of three foundational inventions – the pH meter, the DU spectrophotometer, and the helipot potentiometer – that established the company on a secure financial basis and enabled it to expand.

=== Vitamins ===
Development of the spectrophotometer had direct relevance to World War II and the American war effort. The role of vitamins in health was of significant concern, as scientists wanted to identify Vitamin A-rich foods to keep soldiers healthy. Previous methods of assessing Vitamin A levels involved feeding rats a food for several weeks and then performing a biopsy to estimate ingested Vitamin A levels. In contrast, examining a food sample with a DU spectrophotometer yielded better results in a matter of minutes. The DU spectrophotometer could be used to study both vitamin A and its precursor carotenoids, and rapidly became the preferred method of spectrophotometric analysis.

=== Penicillin ===
The DU spectrophotometer was also an important tool for scientists studying and producing the new wonder drug penicillin.
The development of penicillin was a secret national mission, involving 17 drug companies, with the goal of providing penicillin to all U.S. Forces engaged in World War II. It was known that penicillin was more effective than sulfa drugs, and that its use reduced mortality, severity of long-term wound trauma, and recovery time. However, its structure was not understood, isolation procedures used to create pure cultures were primitive, and production using known surface culture techniques was slow.
At Northern Regional Research Laboratory in Peoria, Illinois, researchers collected and examined more than 2,000 specimens of molds (as well as other microorganisms). An extensive research team included Robert Coghill, Norman Heatley, Andrew Moyer, Mary Hunt, Frank H. Stodola and Morris E. Friedkin. Friedkin recalls that an early model of the Beckman DU spectrophotometer was used by the penicillin researchers in Peoria. The Peoria lab was successful in isolating and commercially producing superior strains of the mold, which were 200 times more effective than the original forms discovered by Alexander Fleming. By the end of the war, American pharmaceutical companies were producing 650 billion units of penicillin each month. Much of the work done in this area during World War II was kept secret until after the war.

=== Hydrocarbons ===
The DU spectrophotometer was also used for critical analysis of hydrocarbons. A number of hydrocarbons were of interest to the war effort. Toluene, a hydrocarbon in crude oil, was used in production of TNT for military use. Benzene and butadienes were used in the production of synthetic rubber. Rubber, used in tires for jeeps, airplanes and tanks, was in critically short supply because the United States was cut off from foreign supplies of natural rubber. The Office of Rubber Reserve organized researchers at universities and in industry to secretly work on the problem. The demand for synthetic rubber caused Beckman Instruments to develop infrared spectrophotometers. Infrared spectrophotometers were better suited than UV–Vis spectrophotometers to the analysis of C4 hydrocarbons, particularly for applications in petroleum refining and gasoline production.