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Extending photochemical measurements into the ultraviolet spectrum
Dr Beckman

“The Spectrophotomer was my most impactful invention - it opened whole new avenues of research and discovery.”

Dr. Arnold O. Beckman

What is a Spectrophotometer?

Chemicals can be identified by how much and what wavelength of light they absorb. A spectrophotometer is a device that shines light of various wavelengths (a spectrum) through a sample, and then measures how much light (using a photometer) passes through the sample. By measuring each wavelength of light individually, a full adsorption spectrum can be graphed, which reveals the type and concentration of chemicals in a solution. Dr. Beckman's groundbreaking Spectrophotometer took this concept into a rugged and reliable bench-top instrument, where by simply turning a dial, an internal prism is rotated, exposing the sample to each wavelength of light.

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Early Spectrophotmetry Systems, 1937-1940

While Dr. Beckman’s pH Meter business is growing year over year, other instrument manufacturers such as General Electric, Cenco, Coleman and Bausch & Lomb, among others, were selling Infrared (IR) and Visible spectrophotometry systems.

Dr. Beckman realized that these systems needed to reach further into the Ultraviolet (UV) spectrum to analyze biological samples, but the UV light sources and compatible optics components for assembling such an instrument did not yet exist.

The Engineering Innovation

In 1977, Dr. Beckman published a retrospective article about the evolution of the UV spectrophometer at Beckman Instruments (formerly National Technical Laboratories) [1], some excerpts are below:

"In 1940, no one at National Technical Laboratories had any extensive experience in spectrophotometry. The fact was recognized, however, that the amplifier of the Beckman pH meter was well suited for use with vacuum-type phototubes. The company began a spectrophotometer development program in early 1940, and the responsibility for this program was assigned to H. H. Cary. Consulting assistance was sought from recognized optical experts, but World War II was under way and experts were hard to find. Roger Hayward, a professional architect and amateur scientist with some optic experience from his association with the Mount Wilson Observatory, provided a needed link to monochromator technology. His genius for quickly translating ideas into useful sketches was partially responsible for the extreme rapidity with which the DU spectrophotometer was developed. Douglas Marlow provided proficiency in mechanical design.

The first instrument designed was a glass Fery prism instrument, but its performance was not considered suitable. A quartz prism Littrow design with a tangent-bar drive followed and was designated the Model Β. Of the two quartz Model Β instruments produced, one was sold to the Chemistry Department of the University of California of Los Angeles in February 1941, and the other is in the company’s historical museum. This instrument utilized a tangent-bar mechanism which provided a substantially linear wavelength scale. Unfortunately, the scale was too compressed, particularly in the ultraviolet region, and was replaced by a Model C with its innovative scroll drive, which was used in all subsequent Beckman quartz prism monochromators. Of the three Model C instruments produced, California Institute of Technology, Vita Foods Co., and Riverside Experiment Station each purchased one. The Caltech instrument was later returned to the company for its museum."

[1] Beckman, A.O., Gallaway, W. S., Kaye, W., and Ulrich, W. F. "History of Spectrophotometry at Beckman Instruments, Inc.". Analytical Chemistry, 49, pp 280A-300A (1977).

Impact of the Beckman DU

Vitamin A Analysis:

The first publication using a Beckman DU was in 1942 for analysis of the Vitamin A content in supplemets being produced for troops in WWII theater [2]. Before the Beckman DU, the assay to test for the concentration of Vitamin A in supplements:

  1. Feed rats a diet rich or poor in your supplement for 3 weeks
  2. Measure the length of tail growth
  3. Correlate amount of bone growth to Vitamin A concentration

After the Beckman DU, the assay to test for the concentration of Vitamin A in supplements:

  1. Dissolve supplement in water
  2. Measure absorption spectra on Beckman DU

Impact: Reduce a 3-week experiment to 10 minutes, with greater accuracy and repeatability

[2] Morgareidge, K. "Influence of the Solvent on the Ultraviolet Absorption Maximum of Vitamin A". Industrial and Engineering Chemistry, 14, pp 700-702 (1942).

Rubber Manufacturing and Quality Control

During WWII, the US natural rubber supply was cut-off and the military began making synthetic rubber. However, the low yield of usable rubber could not meet the needs of the tire supplies to support the war effort.

To ensure quality rubber products, the concentration of butadiene in the source materials needed to be determined. The US Office of Rubber Reserve asked Beckman Instruments to begin construction of IR Spectrophotometers based on the design used by Shell Development Company.

By 1942, Beckman Model IR-1s were used at all synthetic rubber factories to analyze constituent materials during manufacture.

Impact: In-line quality control of manufacturing processes was born!

Overview videos of the UV and IR Spectrophotometers