Quantification\nof Iron(II) in Supplements Using Redox\nTitration and UV–Visible Spectroscopy

This study examined a comprehensive approach to quantifying\niron\nin over-the-counter supplements through two laboratory experiments\ndesigned for undergraduate students in analytical chemistry and instrumental\nanalysis courses. The experiments employed redox titrations and UV–vis\nspectroscopy, reinforcing key techniques, such as titration, solution\npreparation, dilution, glassware handling, and spectroscopic analysis.\nIn the first experiment, students prepared solutions and observed\ncolor changes, indicating the complete oxidation of iron II during\nredox titrations. In the second experiment, students utilized the\nBeer–Lambert law to construct and analyze an external calibration\ncurve with a UV–vis spectrophotometer, enabling the measurement\nof iron levels in the supplements. The students performed a statistical\nanalysis to discuss the mean and variance values between the two methods\nas well as compare their calculated iron amounts with the advertised\nquantity on product labels. The majority of students did not find\na statistically significant difference in the average calculated iron\ncontent for the same analyzed brand between the two techniques. The\naverage for the redox experiment was 67.20 ± 11.45 mg, while\nUV–vis was 63.83 ± 12.38 mg of iron. This experiment was\ndesigned to be adaptable and can include various over-the-counter\nproducts. Additionally, a method using a lower acid concentration\nwas developed to minimize the use of concentrated acid. Although the\nexperiments can be applied as individual experiments, the combination\nof both allowed students to reinforce key statistical techniques through\na comparison of the two procedures. This comprehensive approach caters\nto students across different levels of chemistry courses, from introductory\nto advanced, providing a practical application of theoretical concepts.