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  Home > JCE Print > Journal of Chemical Education > Issues > 2004  > May  >
In the Laboratory
Quantitative Assay for Starch by Colorimetry Using a Desktop Scanner
Kurt R. Mathews, James D. Landmark, and Douglas F. Stickle
Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE 68198-3135
Cover
May 2004
Vol. 81 No. 5
p. 702
Abstract
Solution color change by mixture of iodine with starch is well-known. Here we describe a procedure to produce a standard curve for quantification of starch concentration using colorimetry. The colorimetry is performed by image analysis of a picture of solutions obtained using a desktop scanner. The analysis is performed using a Visual Basic computer program (COLORS.EXE) that measures red, green, and blue pixel intensities from the image. The computer program is provided in Supplemental Material in JCE Online. The lower limit of detection of the described assay is of the order of 10 mg/dL. The measurement of the starch content in potatoes is given as an example. The experiment can serve as an introduction to quantitative analytical chemistry at the high school level and has the desirable feature of using only common and inexpensive reagents. The procedure is likely amenable to further development for other food science experiments.
Supplement
Notes for the instructor, a color image of the microtitre plate containing the stock solutions, and a Visual Basic computer program (colors.exe) for RGB data analysis from a computer image file are available.
*  Contents Folder JCE2004p0702W containing colors.exe and plate.jpg.
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*  Citation
 Mathews, Kurt R.; Landmark, James D.; Stickle, Douglas F. J. Chem. Educ. 2004 81 702.
*  Keywords
 Analytical Chemistry; Carbohydrates; Food Science; General Chemistry; Introductory / High School Chemistry; Laboratory Computing / Interfacing; Laboratory Instruction; Natural Products; UV-Vis Spectroscopy
*  History
 Created:
Last Updated:		 April 1, 2004
February 18, 2005
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