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Iron (Fe) in Vitamins

Iron (Fe) in Vitamins
Contributors
cmwoodbridge
Professor of Chemistry | Georgia Gwinnett College
Beyond Benign
Beyond Benign, Inc.
Learning Objets
Summary
This is an improvement over a similar lab published in Harris’ Analytical Chemistry text. Instead of using organics to form reddish solutions, the catechins or polyphenolic compounds in green tea form colored complexes with iron. UV-Vis spectroscopy in conjunction with Beer’s law can then be used to determine the concentration of Fe in vitamin tablets.

Other authors: Davis Winn (Georgia Gwinnett College)
Keyword Tags
Introduction to Green Chemistry
File (PDF, PPT, image, etc)
greener_tea-draft_03jan23.docx
Learning Goals/Student Objectives
In performing this experiment, a student will…
Be able to apply Beer’s law to construct a calibration curve and determine the concentration of a sample.
Be able to assess the accuracy of their analysis by comparison to published data.
Be able to explain why one solvent is a better choice than another (assuming multiple solvents are used).
Object Type
Laboratory experiment
Audience
Introductory Undergraduate
Common pedagogies covered
Hands-on learning
Green Chemistry Principles
Less Hazardous Chemical Syntheses
Safer Solvents and Auxiliaries
Use of Renewable Feedstocks
Safety Precautions, Hazards, and Risk Assessment
If water is used as a solvent, issues with using acids is eliminated.

Fe(SO2)2(NH4)2*6H2O 10045-89-3
Green tea (dry) from supermarket – Lipton Green Tea
Fe supplement from supermarket – Nature Made Iron 65 mg
Teacher Recommendations or Piloting Data (if available)
See attached document

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Submitted by

cmwoodbridge
Published on
Moderation state
Published
Collection
Greener General Chemistry Labs
Time required (if applicable)
I have performed this in a 1 3-hour lab period with students working in groups of 3-4. Most students finished in 2 hours. I would schedule this lab after a short lab or a lab with wait time so students can prep their vitamin sample prior to doing this lab

Comments

Christine Morales

This works really well and is so green, I'm going to keep using it for the foreseeable future!  (I'm planning to submit an adaptation of this experiment for a 2nd-year analytical laboratory, which is less inquiry-based but also includes a technology component using Python.)

03/19/25 7:11pm
Creative Commons License
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.