A Green Analytical Chemistry Experiment on Paper Devices Using an Unrefined Natural Reagent and a Single Standard Solution

We describe a method for designing green analytical chemistry experiments using lab-on-paper technology and an unrefined natural reagent. Green tea leaf extract, instead of a commercial reagent, was used as the chromogenic reagent to form colored compounds in the microzones of paper devices for the iron assay. The calibration graph was constructed by varying the volume of the iron standard solution dispensed onto the paper zones rather than its concentration. This approach eliminated the need to prepare a series of iron standard solutions with different concentrations. This practice was implemented in the Instrumental Analysis Experiment course to help students understand the principles of lab-on-paper technology, develop hands-on experimental skills and green chemistry literacy, and deepen their comprehension of calibration curves. Forty-five fourth-semester undergraduate students majoring in chemical education participated in this practice. Each student fabricated paper-based devices and used them to detect ferrous iron in ferrous sulfate tablets, a commercial medication for treating iron-deficiency anemia. Positive feedback from the participants confirmed that the intended learning objectives were achieved.