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  Home > JCE Print > Journal of Chemical Education > Issues > 2005  > March  >
In the Laboratory
Separation and Determination of Cr(III) and Cr(VI) with Cation-Exchange Chromatography and Atomic Absorption Spectroscopy. An Experiment for Quantitative Methods of Analysis
Ali Bazzi, Bette Kreuz, James Wuokila, and Ahmed Maqboul
Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, MI 48128
Cover
March 2005
Vol. 82 No. 3
p. 435
Abstract
This article reports on the separation and determination of Cr(III) and Cr(VI) with cation-exchange chromatography and flame atomic absorption spectroscopy. A sample containing the two ions is added to a column containing a cation-exchange resin; the Cr(VI) ions are not retained by the resin and are collected in the effluent. The Cr(III) ions are retained by the resin and eluted with an HCl solution. The separated ions are aspirated into an air/acetylene flame and the absorbance measurements are made at λ = 357.9 nm and 0.2-nm slit width. The experiment has been implemented in a quantitative methods of analysis course. The results of the analysis of synthetic water samples obtained by students majoring in various areas of science are presented. The data showed that 58% of the Cr(VI) and 39% of the Cr(III) values had relative errors in the range of ±5%. The evaluation of the precision of the student results revealed that 48% of the Cr(III) and 81% of the Cr(VI) reported values had RSD ≤ 4%. This experiment introduces the students to the concept of chemical speciation and gives experience in combining analytical techniques to solve chemical problems.
Supplement
Instructions for the students and notes for the instructor are available.
*  Contents JCE2005p0435W.doc (Microsoft Word)
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*  Citation
 Bazzi, Ali; Kreuz, Bette; Wuokila, James; Maqboul, Ahmed. J. Chem. Educ. 2005 82 435.
*  Keywords
 Analytical Chemistry; Atomic Spectroscopy; Chromium; Ion Exchange; Quantitative Analysis
*  History
 Created:
Last Updated:		 February 2, 2005
February 18, 2005
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