A General Chemistry Laboratory Experiment Investigating Total Nitrates and Nitrites in Vegetables and Meats through Redox Chemistry and UV–Visible Spectroscopy

Authors

• Mutuku John, Marquette University
• Farouk Awudu, Oklahoma State University
• Asfaha Iob, Oklahoma State University
• Jacinta M. Mutambuki, Marquette UniversityFollow

Document Type

Article

Publication Date

4-2026

Publisher

American Chemical Society

Source Publication

Journal of Chemical Education

Source ISSN

0021-9584

Abstract

This laboratory experiment introduces General Chemistry I students to the determination of total nitrate and nitrite concentrations in common food samples, offering a context that connects chemical analysis to nutrition, food preservation, and public health. Students work collaboratively to design extraction methods for vegetables and meats, followed by the reduction of nitrate (NO₃^–) to nitrite (NO₂^–) using zinc in the presence of a manganese catalyst. Following the chemical reduction of nitrate to nitrite, the combined nitrate and nitrite content of food samples was quantified via diazotization and UV–visible spectrophotometry. The resulting nitrite undergoes diazotization with sulfanilamide and subsequent coupling with N-(1-naphthyl) ethylenediamine to produce a red azo dye. The dye is analyzed using UV–visible spectroscopy at 540 nm, allowing students to apply Beer’s Law to determine total nitrate and nitrite concentrations quantitatively. The experiment reinforces key chemical concepts, including oxidation–reduction processes, intermolecular forces, catalysis, and quantitative spectroscopy, while enhancing students' scientific practices and skills. Whole-class discussions extended the investigation to the societal and biological implications of dietary nitrate and nitrite, including their dual roles as essential nutrients and potential health risks such as methemoglobinemia and nitrosamine formation. Our initial implementation demonstrated that students not only developed a stronger conceptual understanding but also gained practical skills in instrumentation, experimental design, and collaborative problem-solving in a meaningful, real-world context.

Comments

Accepted version. Journal of Chemical Education, Vol. 103, No. 5 (April 2026): 2688-2695. DOI. © 2026 American Chemical Society and Division of Chemical Education Inc. Used with permission.

Recommended Citation

John, Mutuku; Awudu, Farouk; Iob, Asfaha; and Mutambuki, Jacinta M., "A General Chemistry Laboratory Experiment Investigating Total Nitrates and Nitrites in Vegetables and Meats through Redox Chemistry and UV–Visible Spectroscopy" (2026). Political Science Faculty Research and Publications. 160.
https://epublications.marquette.edu/polisci_fac/160