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UV-The Instrument-Handout CC-BY-NC-ND Page 1 of 5 | Lecture Slides for “The UV-vis Spectrometer” | Barry Linkletter | [email protected] The UV-vis Spectrometer We need a machine to measure UV spectra. How would you build one? Part 1: A Brief History The Beckman DU Spectrophotometer The Spectronic 20 in 1666, Newton showed that white light was a In 1940 Arnold Beckman, already rich from his Since 1953, Bausch & Lomb introduced the continuum of many colors. Then he invented invention of the pH meter, developed a benchtop spectronic 20 and it remains a common the rest of modern science and calculus. spectrophotometer. With it, he got even richer sight in chemistry labs. It is still being made Many other great minds further and used it to win WW2. today in an updated form. Do you recognize Image of a Beckman DU spectrometer obtained from “Arnold O. Beckman and the Spectrophotometer”, developed the theory of light and Goad, G. weblog entry, Biosurplus catalogue, September 15th, 2011. Accessed at http://www.biosurplus.com/blog/arnold-o-beckman-and-the-spectrophotometer/ on April 8, 2014 this model? electromagnetic energy — the list Actually, fiberglass is too large to write out here. won WW2 for us. No, penicillin won WW2 An image of Isaac Newton on a British stamp. Image for accessed at http://www4.ncsu.edu/~kimler/hi322001/pophero.html on April 8, 2014 This appears to be a collection of images for a history course by Dr. William Kimler (http://history.ncsu.edu/faculty/view/william_kimler1) at North Carolina State University. Can we all just agree that chemists won WW2? 19th century technology involved prisms, telescopes A Portrait of Arnold O. Beckmann (c. 1930s) from the Special Collections & Archives Research Center, The Valley Library, Oregon State University and protractors. Eventuall photographic film was This photo is from the collection “The Scientific War Work of Linus C. Pauling: A Documentary History” at http://scarc.library.oregonstate.edu/coll/pauling/ Accessed at http://scarc.library.oregonstate.edu/coll/pauling/war/pictures/portrait-beckman-large.html used to visualize the UV spectrum. That’s on April 8, 2014 ancient history. Image of a Thermo Scientific Spectronic 20D spectrometer from the Scientis International catalogue http://scientiis.com/laboratorium/catalog/product_info.php?manufacturers_id=165&products_id=14861 Accessed at http://scientiis.com/laboratorium/catalog/images/Laboratory/333183.jpg on April 8, 2014 Tungsten lamp Hmmm... does this Entrance slit look familiar to you? Lens Lens Lens Pro tip: get a nice portrait of yourself Exit slit now, while you are Variable stop Diffraction Now that’s Test tube Arnold Beckman, young and beautiful. Filters 100%T adjustment grating craftsmanship! Optical diagram of a Spectronic 20 spectrophotometer. Adapted from a similar circa 1920. Photodetector diagram in the “SPECTRONIC 20+ and SPECTRONIC 20D+ User Guide”, Thermo Scientific, 2007. Accessed at http://www.seas.upenn.edu/~belab/equipment/equipment_links/Spec20_Manual.pdf on April 8, 2014 Image of the Beckmann Bulletin from the “Visible Proofs: Forensic Views of the Body” exhibition at the National Library of Medicine that closed on February 25, 2008. Accessed at https://www.nlm.nih.gov/visibleproofs/galleries/technologies/spectral_image_6.html John Browning’s dual Also in 1953, Bausch & Lomb invented prism spectroscope, Image of poster for a John Browning Multi-prism Automatic Laboratory Spectroscope c. 1875 from Allan Wissner, “Chemistry Related Antique Optical Instruments”, weblog, the Cinemascope camera lense and c. 1870. http://www.antique-microscopes.com/chemistry/ B Accessed April 8, 2014 Image of a John Browning Multi-prism Automatic Laboratory Spectroscope c. 1875 from Allan Wissner, “Chemistry Related Antique Optical Instruments”, weblog, A: light source introduced the wide screen format. http://www.antique-microscopes.com/chemistry/ B: mirror Accessed April 8, 2014 F C: mirror They won a A D: entrance and exit ports technical Oscar E E: concave mirror for this. G F: quartz prism G: cell compartment D C H H: photomultiplier tube Diagram of a Beckmann DU Spectrometer. Adapted from figure 6 in “The Physical Methods For The Identification of Narcotics. Part IIIA. The Ultraviolet Spectrophotometric Method”, Charles G. Farmilo, United Nations Office on Drugs and Crime: Bulletin on Narcotics, 1954, 3, 18-39 Through the 1940’s and 50’s this Accessed at https://www.unodc.org/unodc/en/data-and-analysis/bulletin/bulletin_1954-01-01_3_page005.html on April 8, 2014 The video is available on YouTube at spectrometer changed the course https://youtu.be/-GXCINeq634 of chemistry. Ever wonder why Movie poster from “Famous Movie Posters of Filmland” everything in the classics of physical Accessed at http://www.jimzippo.com/page7.html pn April 8, 2014 organic chemistry involves a phenyl group? KeynoteChemistry.com Page 2 of 5 | Lecture Slides for “The UV-vis Spectrometer” | Barry Linkletter | [email protected] The UV-vis Spectrometer You just gotta have one. What’s in your lab? Howard didn’t take my advice and get a The monochrometer portrait done in his Single Beam here uses a reflective younger days. Maybe he did, but I keep getting diffraction grating to Part 2: Modern UV-vis Instruments pictures of Cary disperse the light beam. Grant when I search... CARY 50 UV-vis Image of a CARY 50 UV-vis spectrometer from Varian sales brochure. Accessed at There are three kinds: Sample https://www.chem.agilent.com/Library/brochures/Cary%2050%20UV-Vis-brochure.pdf on April 8, 2014 1) single beam instruments Monochromator Detector 2) expensive, highly precise dual beam instruments Exit slit Rotating the grating 3) less expensive, more robust will cause light of diode array instruments. Dispersion Source device different wavelengths Diagram adapted from “Fundamentals of modern UV-visible spectroscopy: A primer”, to pass through the A spectrometer exists for every use Entrance Tony Owen, Agilent Technologies, 2000 ,p37, Figure 23, Accessed at http://www.chem.agilent.com/Library/primers/Public/59801397_020660.pdf and budget. There are fiber optic slit slit. Image of a CARY 300 UV-vis spectrometer from Varian Australia sales brochure. attachments, movable multicell holders, Howard Cary Accessed at http://people.stfx.ca/tsmithpa/Chem361/Labs/1604.pdf on April 8, 2014 temperature controllers, and all He was the engineer who The dual beam allows developed the Beckmann DU CARY 300 UV-vis kinds of other accessories. and then started his own Dual Beam for a reference company. The spectrometers measurement to be on this page still bear his name. Image of Howard Cary from “Fellows Profile: Howard Cary”, taken constantly. Godfrey, T., Optical Society of Southern California, Accessed at http://www.ossc.org/content.aspx?page_id=22&club_id=239344&module_id=61898 on April 8, 2014 Monochromator Exit Do you think the lamp slit provides perfectly Reference constant signal strength? Dispersion You don’t have to think device about that with Entrance dual beams. Chopper Source slit Detector The Most Important Accessory Diagram adapted from “Fundamentals of modern UV-visible spectroscopy: A primer”, Tony Owen, Agilent Technologies, 2000 ,p41, Figure 26, Accessed at http://www.chem.agilent.com/Library/primers/Public/59801397_020660.pdf You need a cell to put your sample in. Surprising science career: Fancy dual chopper Quartz is a common choice. Scientific glass blowing. Sample Try fusing a quartz UV window mirrors will turn heads 100 on the highway. into a glass apparatus. Madness!! Diode Array Agilent 5453 DAD UV-vis Fused Check out Chem. Eng. News, 2006, 84(3), 9-15 Agilent used to be silica https://pubs.acs.org/cen/coverstory/84/8403glassblowing.html Hewlett-Packard. ] Shutter 80 for more information. They bought Varian, Lens [% who had purchased e Sample Fused the CARY line. nc quartz a t t 60 The diode array i Tungsten Lens m lamp Slit Grating s does away with n a r Deuterium expensive moving T 40 Acrylic Glass lamp parts. But it’s plastic resolution is limited 20 We can measure the to the # of light whole spectrum at once. Optical 1024-element Ask yourself how This allows for many this is similar to the sensors on the chip. glass diode array Image of Agilent 8453 UV-Vis Spectrophotometer from the University of repeated complete spectra photographic film Chicago Biophysics Department at http://biophy.uchicago.edu/index.php 0 Accessed at http://biophy.uchicago.edu/spec.php on April 8, 2014 to be collected. This is used to record spectra 200 250 300 350 400 perfect for a HPLC detector. 100 years ago. You can build your own spectrometer. Here is a place to start: ”Build your own spectrophotometer”, S.J. Tavener, J.E. Thomas-Oates, Wavelength [nm] Diagram adapted from “Fundamentals of modern UV-visible spectroscopy: A primer”, Tony Owen, Agilent Technologies, 2000 ,p40, Figure 25, , 44(5), 151-154 Accessed at http://www.chem.agilent.com/Library/primers/Public/59801397_020660.pdf Education in Chemistry, 2007 Page 3 of 5 | Lecture Slides for “The UV-vis Spectrometer” | Barry Linkletter | [email protected] The UV-vis Spectrometer The dark heart of your instrument: the monochrometer A diffraction grating in action. It’s all about d sin r = m = 500 10 9 m being regular. m = 0 = A picture speaks r 24.6 This is basically Part 3: Sifting and sorting for science 56.4 ˚ m = 1 24.6 ˚ 9 louder than words. the ordinary = 500 10 m reflection of the incident beam. A monochromater does just what the First = Spectra is the result r 56.4 order name implies — it chooses a wavelength of diffraction from Second m = 2 spectra of light. By scanning the monochromater the regularly spaced order we can measure the absorbance at lines on the grating. Zero spectra order many wavelengths and get a spectrum. spectra Concave mirror Concave mirror d = 1.2 10 6 m d = 1.2 10 6 m Incident light of The incident What if the light strikes wavelength l is light hits the at an angle? perpendicular grating in phase to the grating This difference in distance travelled defines the phase The diffracted light "diffraction grating".Photograph.
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