In the Laboratory
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Modeling the Effect of Polychromatic Light in Quantitative Absorbance Spectroscopy Rachel Smith and Kevin Cantrell* Department of Chemistry, The University of Portland, Portland, OR 97203; *
[email protected] This laboratory experiment gives students practical experience with the principles of electronic absorbance spectroscopy including the components of a spectrophotometer, the Beer–Lambert law, deviations from linearity, and figures of merit. In addition to these fundamental topics, the lab introduces some of the concepts of “lab-on-a-chip” technology and environmental chemistry. The current emphasis on decreasing the size and cost of instrumentation has biological, pharmaceutical, and environmental applications (1, 2). Removing the monochromator and replacing the continuum light source found in traditional spectrophotometers with a LED can reduce the size and cost of the instrument by orders of magnitude (3). Iron has been identified as a biolimiting nutrient in oceans, a terminal electron acceptor in the metabolism of an entire class of microorganisms and a promising means to ameliorate the impact of pollutants in groundwater. From CO2 sequestration to acid mine drainage, redox and precipitation reactions involving iron appear again and again in environmental chemistry (4–6). The speciation of iron in these systems depends on ambient redox and pH conditions. In general, soluble Fe(II) is found in reducing environments at low to intermediate pH values (
