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2007
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In the Laboratory
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Modeling the Effect of Polychromatic Light in Quantitative Absorbance Spectroscopy
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Rachel Smith and Kevin Cantrell
Department of Chemistry, The University of Portland, Portland, OR 97203
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June 2007
Vol. 84 No. 6
p. 1021
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| Abstract |
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This laboratory experiment is the first in a semester-long instrumental analysis course. Students measure the emission profiles of various light sources including light-emitting diodes (LEDs), the transmission of interference and absorption filters, and the absorptivity of colored complexes of Fe2+. They use this information to model the effect of polychromatic radiation on the shape of the calibration curve and to assess possible optical configurations for a field spectrophotometer used to determine the concentration of soluble iron in environmental systems. This experiment serves as a hands-on examination of many of the fundamental concepts in electronic absorbance spectroscopy. The typical components of a spectrophotometer and their functions are clearly illustrated (e.g., continuum vs line sources, filters vs monochromators). Topics in quantitative absorbance spectroscopy including Beer's law, deviations from linear behavior, and figures of merit are also covered. The students gain experience with the use of spreadsheets for data analysis and macro programming in Excel. The data collected in this lab are applied to current topics in analytical research including environmental analysis and the miniaturization of analytical instruments.
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| Supplement |
A brief discussion of the derivation of eq 1, a detailed description of the procedure, a prelab worksheet, typical student results, and a description of the Excel macro and an electronic version are available.
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| More Information |
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Citation |
Smith, Rachel; Cantrell, Kevin. J. Chem. Educ. 2007, 84, 1021.
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Keywords |
Analytical Chemistry; Calibration; Computer-Based Learning; Coordination Compounds; Hands-On Learning / Manipulatives; Instrumental Methods; Laboratory Instruction; Quantitative Analysis; Spectroscopy; Upper-Division Undergraduate
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History |
Created:
Last Updated: |
4/24/2007
5/3/2007
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 Caution! | | Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations. |
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