DU spectrophotometer
This model of spectrophotometer enabled scientists to easily examine and identify a given substance based on its absorption spectrum, the pattern of light absorbed at different wavelengths.
The Beckman DU was essential to several critical secret research projects during World War II, including the development of penicillin and synthetic rubber.
Before the development of the DU spectrophotometer, analysis of a test sample to determine its components was a long, costly, and often inaccurate process.
Biological molecules, including proteins and nucleic acids, absorb light energy in both the ultraviolet and visible range.
Existing instruments such as the Cenco "Spectrophotelometer" and the Coleman Model DM Spectrophotometer could not be effectively used to examine wavelengths in the ultraviolet range.
[11][12] The array of equipment needed to measure light energy reaching beyond the visible spectrum towards the ultraviolet could cost a laboratory as much as $3,000, a huge amount in 1940.
[2]: 149 Repeated readings of a sample were taken to produce photographic plates showing the absorption spectrum of a material at different wavelengths.
Ultimately, the accuracy of such approaches was dependent on accurate, consistent development of the photographic plates, and on human visual acuity and practice in reading the wavelengths.
Seeing the potential to build upon their existing expertise, Beckman made it a goal to create an easy-to-use integrated instrument which would both register and report specific wavelengths extending into the ultraviolet range.
In developing the Model D, Beckman took the direct-coupled amplifier circuit from the pH meter and combined the optical and electronic components in a single housing, making it more economical.
When they turned down the opportunity, National Technical Laboratories designed its own optical system, including both a control mechanism and a quartz prism.
[17]: 17 Beckman had previously attempted to find a source of reliable hydrogen lamps, seeking better sensitivity to wavelengths in the ultraviolet range than was possible with tungsten.
As described in July 1941, the Beckman spectrophotometer could use a "hot cathode hydrogen discharge tube" or a tungsten light source interchangeably.
[2]: 153–155 [17]: 17–18 When RCA could not meet Beckman's demand for experimental phototubes, National Technical Laboratories again had to design its own components in-house.
[17]: 18 They developed a pair of phototubes, sensitive to the red and blue areas of the spectrum, capable of amplifying the signals they received.
This allowed the user to plot the light absorption spectrum of a substance to obtain a standardized "fingerprint" characteristic of a compound.
[41] The DU spectrophotometer's manual scanning method was extremely fast, reducing analysis times from weeks or hours to minutes.
[35]: 141 Credited with having "brought about a breakthrough in optical spectroscopy",[5]: 10 the Beckman DU has been identified as "an indispensable tool for chemistry"[2]: 207 and "the Model T of laboratory instruments".
With the DU's UV technology, vitamin A content of shark liver oil could be determined directly in a matter of minutes.
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.
"[42][43] Inorganic chemist and philosopher of science Theodore L. Brown states that it "revolutionized the measurement of light signals from samples".
[46]: 2 Nobel laureate Bruce Merrifield is quoted as calling the DU spectrophotometer "probably the most important instrument ever developed towards the advancement of bioscience.
"[12] 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.
[54] An extensive research team included Robert Coghill, Norman Heatley, Andrew Moyer, Mary Hunt,[55][56][57] Frank H. Stodola and Morris E. Friedkin.
[52]: 316 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.
[62][63] "The enzyme could be assayed in a few minutes by coupling it to isocitrate dehydrogenase and in measuring the NADH formed using the Beckman DU spectrophotometer, an instrument that transformed biochemistry.
[70] Particularly useful in detecting conjugated double bonds, the new technology made it possible for researchers like Ralph Holman and George O. Burr to study dietary fats, work that had significant implications for human diet.
[71] The DU spectrophotometer was also used in the study of steroids[72][73] by researchers like Alejandro Zaffaroni,[74] who helped to develop the birth control pill, the nicotine patch, and corticosteroids.
[75] The Beckman team eventually developed additional models, as well as a number of accessories or attachments which could be used to modify the DU for different types of work.
[76]: 21 The DK's speed made it preferred to the DR.[16] Kaye eventually developed the DKU, combining infrared and ultraviolet features in one instrument, but it was more expensive than other models.
