Green Analytical Chemistry Experiment: Quantitative Analysis of Iron in Supplement Tablets with Vis spectrophotometry Using Tea Extract as a Chromogenic Agent

Abstract

Copyright © 2019 American Chemical Society and Division of Chemical Education, Inc. A green chemistry experiment is presented for teaching an undergraduate quantitative analysis/analytical chemistry laboratory class through the use of black tea leaf extract for the determination of iron in supplement tablets. Dried tea leaf is a safe, low cost, and widely available source of natural extract that can be used in place of more toxic chemicals (for example, 1,10-phenanthroline) or other uncommon natural reagents that may be hard to obtain outside their native lands. Various student learning outcomes accommodated within this experiment include the principles and hands-on operation of a spectrophotometer, the construction of a calibration graph and obtaining a linear regression equation using Microsoft Excel, the determination of figures of merit (limit of detection, limit of quantitation, and linear working range), and sampling and preparation of supplement tablets with acid digestion. Students were trained in quality control and quality assurance through statistical data analysis for precision (SD) and accuracy (t test, percent recovery, and percent error) for the experiment. They were asked to discuss not only advantages but also limitations of using natural reagents for chemical analysis. Critical thinking and a deep understanding of the experiment were assessed through the students' ability to answer follow-up questions in their report and on the exam. Class management and modification of the experiment to suit a laboratory with limited facilities are discussed. This robust tea-Fe experiment was successfully demonstrated for teaching both large and small laboratory classes at two institutions, one in the U.S. and one in Thailand.