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

Abstract

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.

Quantification of Nitrite in Food and Water Samples Using the Griess Assay and Digital Images Acquired Using a Desktop Scanner

“…Here, the official method was scaled down, and it used just 0.2 mL of the Griess reactant and 1 mL of sample. Scaling the method down results in less waste generated after each class, reduced cost of treating waste and buying reactants, and reduced risks to students and educators from hazardous chemicals …”

“…Scaling the method down results in less waste generated after each class, reduced cost of treating waste and buying reactants, and reduced risks to students and educators from hazardous chemicals. 23 When we proposed this laboratory class for the first time, students brought water samples from wells and lakes close to their homes. Normally, in Brazil, the nitrite concentration in water is lower than 1 μmol/L and we just found one water sample that had nitrite concentrations higher than the method QL.…”

Iron Quantification in Dietary Supplements using Four Colorimetric Assays

“…Iron was quantified in water and dietary supplements , using green tea as the chromogenic reagent, where the gallic acid present in green tea was responsible for color development. In these studies, the violet-colored complexes had their λ max values in the 550–570 nm range.…”

Lab-at-Home: Hands-On Green Analytical Chemistry Laboratory for New Normal Experimentation

“…The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/su14063314/s1, File S1: instruction of the LAH experiment (in Thai); Video S1: demonstration of the determination of dye concentration using the LAH box set; Video S2: demonstration of the determination of iron concentration using the LAH box set; Video S3: a group of students performing the hands-on LAH experiment; Video S4: students individually performing the LAH experiment. References [12,13,[24][25][26][27][28][29][30] are cited in the supplementary materials.…”