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The Chemical Educator
ISSN: 1430-4171 (electronic version)
Abstract Volume 18
(2013) pp 104-106
DOI 10.1007/s0089713248078
Anion-Exchange Separation and Complexometric Titrations: An Analytical Chemistry Experiment
William R. Furlong and Ramee Indralingam*
Department of Chemistry, Stetson University, DeLand, FL 32723, rindrali@stetson.edu Received December 20, 2012.
Accepted March 16, 2013.
Published: 3 May 2013
Abstract. Chromatography and complexation titrations are important topics in the analytical chemistry curriculum. We have developed an experiment that uses anion-exchange chromatography to separate transition metal ions that form anionic chloro-complexes depending on the concentration of hydrochloric acid present in the mixture. Ni(II) and Zn(II) are separated by elution with 2M HCl and 6M NH3 respectively. The separated ions are buffered to a suitable pH and titrated with EDTA for quantitative analysis. This laboratory experiment is effective in illustrating to students the principles of chromatography, including the importance of efficient packing in chromatography columns, the reason for optimum flow rate, the importance of taking into consideration the capacity of the stationary phase and the composition of the mobile phase. Students are also exposed to important aspects of metal-chelate complex formation such as the use of auxiliary complexing agents, the necessity for a suitable indicator that will not be blocked by the metal, and the reason for being able to use larger amounts of indicator than in traditional acid-base titrations. This lab experience serves as a useful introduction to the in-depth treatment of chromatography in the following year’s instrumental analysis course.
Key Words: Laboratories and Demonstrations; analytical chemistry; ion exchange chromatography; titration
(*) Corresponding author. (E-mail: rindrali@stetson.edu)
Article in PDF format (26 KB) HTML format
Supporting Materials:
Student handout including post lab questions; notes for the instructor including details of column parameters and anion exchange resin, and answers to post lab questions are available (130 KB).
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