Description: The DU Series Spectrophotometer is a microprocessor- controlled spectrophotometer intended for use in quantitative and qualitative biological. The Beckman DU Spectrophotometer is an efficient stand alone system that comes with complementary accessories to produce accurate results. Beckman DU UV/Vis Scanning Spectrophotometer. This refurbished DU Spectrophotometer unit; PDF Manual; Mouse; Power cord.
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The DU spectrophotometer or Beckman DUintroduced inwas the first commercially viable scientific instrument for measuring the amount of ultraviolet light absorbed by specrtophotometer substance.
This model of spectrophotometer enabled veckman to easily examine and identify a given substance based on its absorption spectrumthe pattern of light absorbed at different wavelengths. Beckman ‘s National Technical Laboratories later Beckman Instruments developed three in-house spectrlphotometer models A, B, C and one limited distribution model D before moving to full commercial production with the DU. Approximately 30, DU spectrophotometers were manufactured and sold between and Sometimes referred to as a UV—Vis spectrophotometer because it measured both the ultraviolet UV and visible spectra, the DU spectrophotometer is credited as being a truly revolutionary technology.
It yielded more accurate results than previous methods for determining the chemical composition of a spectrophotometr substance, and substantially reduced the time needed for an accurate analysis from weeks or hours to minutes.
The Beckman DU was essential to several critical secret research projects during World War IIincluding the development of penicillin and synthetic rubber. Before the development of spectropjotometer DU spectrophotometer, analysis of a test sample to determine its components was a long, costly, and often inaccurate process.
A classical wet laboratory contained a wide variety of complicated apparatus. Determining quantitative concentrations of those components in the sample involved further steps.
Processes could involve techniques for chemical reactionsprecipitationsfiltrations and dissolutions. Spectroscopic methods for observing the absorption of electromagnetic radiation in the visible spectrum were known as early as the s. A white light source would emit light at multiple wavelengths over a range of frequencies.
A prism could be used to separate a light source into specific wavelengths. Shining the light through a sample of a material would cause some wavelengths of light to be absorbed, while others would be unaffected and continue to be transmitted.
Wavelengths in the resulting absorption spectrum would differ depending upon the atomic and molecular composition if the material involved. Spectroscopic methods were predominantly used by physicists and astrophysicists. Spectroscopic techniques were rarely taught in chemistry classes and were unfamiliar to most practicing chemists.
By the s, both academic and industrial chemists were becoming increasingly interested in problems involving the composition and manuual of specrophotometer molecules. Biological molecules, including proteins and nucleic acidsabsorb 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.
An experienced human could compare these to the known images to identify a match. Then information from the plates had to be combined to create a graph showing the spectrum as a whole. 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. Coleman Instruments had recently coupled a pH meter with an optical phototube unit to examine the visual spectrum the Coleman Model DM.
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.
Rather than depending on development of photographic plates, or a human observer’s visual ability to detect wavelengths in the absorption spectrum, phototubes would be used to register and report the specific wavelengths that were detected.
This had the potential to increase the instrument’s accuracy and reliability as well as its speed and ease of use. The first spectrophotomster Beckman spectrophotometer, the Model A, was created beckmwn National Technologies Laboratories in It used a tungsten light source with a glass Fery prism as a monochromator.
Tungsten lamps were useful in the visible light range but gave poor coverage in the ultraviolet range. However, they had the advantage of being readily available because they were used as automobile headlamps. It was quickly realized that a glass dispersive prism was not suitable for use in the ultraviolet spectrum. A tangent bar mechanism was used to adjust the monochromator. The mechanism was highly sensitive and required a skilled operator. The Model B prototype should be distinguished from a later production model of spectrophotometer that was also referred to as the Model “B”.
The production Model “B” was introduced in as a less-expensive, spectrophotometed alternative to the Beckman DU.
Three Model C instruments were then built, improving the instrument’s wavelength resolution.
The Model B’s rotary cell compartment was replaced with a linear sample chamber. The tangent bar mechanism was replaced by a scroll drive mechanism, : This set the pattern for all of Beckman’s later quartz prism instruments. The A, B, and C prototype models all coupled an external Beckman pH meter to the optical component to obtain readouts.
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. Moving from a prototype to production of the Model D involved challenges. Beckman originally approached Bausch and Lomb about making quartz prisms for the spectrophotometer.
When they turned down the opportunity, National Technical Laboratories designed its own optical system, including both a control mechanism and a quartz prism. Large, high optical quality quartz suitable for creating prisms was difficult to obtain. It came from Brazil, and was in demand for wartime radio oscillators.
Beckman had to obtain a wartime priority listing for the spectrophotometer to get access to suitable quartz supplies. Beckman had previously attempted to find a source of reliable hydrogen lampsseeking better sensitivity to wavelengths in the ultraviolet range than was possible with tungsten. As described in Julythe Beckman spectrophotomter could use a “hot cathode hydrogen discharge tube” or a tungsten light source interchangeably.
National Technical Laboratories designed its own hydrogen lamp, an anode enclosed in a thin blown-glass window.
The instrument’s design also required a more sensitive phototube than was commercially available at that time. Beckman was able to obtain small batches of an experimental phototube from RCA for the first Model D instruments. In it, Cary and Beckman compared designs for a modified self-collimating quartz Fery prism, a mirror-collimated quartz Littrow prismand various gratings. The Model D was the first model to enter actual production.
A small number of Model D instruments were sold, beginning in Julybefore it was superseded by the DU. When RCA could not meet Beckman’s demand for experimental phototubes, National Technical Laboratories again had to design its own components in-house. The DU spectfophotometer the bckman commercially viable scientific instrument for measuring the amount of ultraviolet light absorbed by a substance.
One of the first fully integrated instruments : It is generally assumed that the “DU” in the name was a combination of “D” for the Model D on which it was based, and “U” for the ultraviolet spectrum.
A publication in the scholarly literature compared the optical quality of the DU to the Cary 14 Spectrophotometeranother leading UV—Vis spectrophotometer of the time. From untilwhen it was discontinued, the Model DU spectrophotometer was built upon what was essentially the same design. This allowed the user to plot the light absorption spectrum of a substance to obtain a mamual “fingerprint” characteristic of a compound. The entrance mirror deflects the light through the entrance slit and into the monochromator to the collimating mirror.
Light falling on the collimating mirror is rendered parallel and reflected to the quartz prism where it undergoes refraction. The back surface of the prism is aluminized so that light refracted at the first surface is reflected back through the prism, undergoing further refraction as it emerges from the prism. The desired wavelength of light is selected by rotating the Wavelength Selector which adjusts the position of the prism.
The spectrum is directed back to the collimating mirror which centers the chosen wavelength on the exit slit and sample.
Spectrophotometer, DU – OpenWetWare
Light passing through the sample strikes the phototube, causing a current gain. The current gain is amplified and registered on the null meter. Although the default light source for the instrument was tungsten, a hydrogen or mercury lamp could be substituted depending on the optimal range of measurement for which the instrument was to be used. As advertised in the News Edition of the American Chemical Society, the Beckman Spectrophotometer used an autocollimating quartz crystal prism for a monochromator, capable of covering a range from the ultraviolet millimicrons to the infrared millimicronswith a nominal bandwidth of 2 millimicrons or less for most of its spectral range.
The slit mechanism was continuously adjustable from. The sample holder held up to 4 cells. This enables the ratio, transmittanceto be obtained. For quantitative measurements transmittance is converted to absorbance which is proportional to the solute concentration according to Beer’s law.
This makes possible the quantitative determination of the amount of a substance in solution. The user could also switch between phototubes without removing the sample holder.
A advertisement indicates that three types of phototubes were available, with maximum sensitivity to red, blue and ultraviolet light ranges. The DU spectrophotometer differs in that it claims to be useful from to millimicrons, : 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.
It was accurate in both the visible and ultraviolet ranges. Other advantages included its high resolution and the minimization of stray light in the ultraviolet region. Credited with having “brought about a breakthrough in optical spectroscopy”, : 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 oilbefore 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.
Organic chemist and philosopher of science Theodore L. Brown states that it “revolutionized the measurement of light signals from samples”. Morris identifies the introduction of the DU and other scientific instruments in the s as the beginning of a Kuhnian revolution. For the Beckman company, the DU was one of three foundational inventions — the pH meterthe DU spectrophotometer, and the helipot potentiometer — that established the company on a secure financial basis and enabled it to expand.
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 was also an important tool for scientists studying and producing the new wonder drug penicillin. Forces engaged in World War II.