At-Home Colorimetric and Absorbance-Based Analyses: An Opportunity for Inquiry-Based, Laboratory-Style Learning

In light of COVID-19 in spring 2020, we developed a simple and versatile inquiry-based, laboratory-style active learning colorimetry experiment amenable to at-home quantitative analysis. In this experiment, students acquire an external calibration method using aqueous solutions of a self-selected chromophoric analyte from household products using a smartphone camera and RGB image analysis. We report typical student-obtained results for a 5 point external calibration method using RGB image analysis and solutions prepared with green food colorant and blue food colorant. Solutions were prepared using common kitchen measuring tools, glass drinking cups served as sample cells or cuvettes, images were acquired with a smartphone camera, and image analyses were conducted using RGB analysis software. Results show analytical data can be readily obtained for both colorimetric and absorbance-based analyses. Experientially, results show that throughout method development students are challenged with various quantitative analysis learning objectives, including basic concepts about light matter interactions, analytical solution preparation, chemical concentrations, unit analysis, significant figures, statistical analysis, and analytical figures of merit (i.e., method robustness, linearity, and sensitivity, etc.). Furthermore, by bringing chemistry into the home, students are challenged to be creative and access a wide range of problem-solving and critical thinking skills, some of which may not be exercised in traditional laboratory experiments and projects.