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  Home > JCE Print > Journal of Chemical Education > Issues > 2001  > November  >
In the Laboratory
Topics in Chemical Instrumentation
Applied Electronics: Construction of a Simple Spectrophotometer
Melissa A. Thal
Department of Chemistry, Indiana University, Bloomington, IN 47405

Michael J. Samide
Department of Chemistry, Butler University, Indianapolis, IN 46208
Cover
November 2001
Vol. 78 No. 11
p. 1510
Abstract
In this paper we describe the construction of a simple spectrophotometer intended for use as a capstone circuit for an electronics laboratory exercise. Students in the undergraduate laboratory have learned basic circuitry and are now able to read a schematic and construct an instrument that has practical applications in chemical analysis. A simple LED is used as the source and is easily changed to correspond to different species being studied. Detection is accomplished through the use of one of three signal transducers (a photoresistor, a photodiode, or a photodarlington) and a current-to-voltage converter. A box lined with black felt is used to shield the spectrophotometer from ambient light. This spectrophotometer shows excellent Beer-Lambert law linearity over a large concentration range and has been used in the laboratory to determine the concentration of a metal cation in solution on the basis of a calibration curve. Of the transducers used, the photoresistor showed the best response at multiple wavelengths with error in concentration determination not greater than 6%. Through the building and testing of this circuit, the students can visualize applications of electronic circuitry.
Supplement
A handout for students, a materials and equipment list, and notes for the instructor are available.
*  Contents JCE2001p1510W.doc (Microsoft Word)
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*  Citation
 Thal, Melissa A.; Samide, Michael J. J. Chem. Educ. 2001 78 1510.
*  Keywords
 Instrumental Methods; Laboratory Equipment / Apparatus; UV-Vis Spectroscopy
*  History
 Created:
Last Updated:		 October 8, 2001
August 31, 2005
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