Validated Smartphone Digital Image Colorimetry for Authentic Instrumental Analysis Learning

Instrumentation literacy is a central goal of undergraduate chemistry education, yet access to conventional analytical instruments remains uneven across teaching laboratories. This study examined smartphone-based digital image colorimetry as both a validated analytical workflow and a learning environment for undergraduate instrumental analysis. The workflow combined a controlled optical chamber, region-of-interest selection, RGB signal extraction, channel optimization, calibration, and comparison with UV–Vis spectrophotometry. The strongest calibration response occurred under the green-background/blue-channel condition, with the smartphone method showing strong calibration fit and repeatability across the selected working range, whereas UV–Vis retained greater sensitivity at lower concentrations. The instructional implementation involved 65 undergraduate students completing sample preparation, image capture, RGB extraction, calibration, method comparison, and reporting. Conceptual performance improved significantly from pretest to posttest, with favorable mastery-level shifts and item-level gains concentrated in calibration- and signal-related concepts. Practical performance was strongest in measurement, calibration, and LOD/LOQ-related tasks, while accuracy evaluation, conclusion writing, and higher-order interpretation remained more challenging. Overall, the validated smartphone workflow was analytically credible under controlled conditions and pedagogically meaningful, offering a scalable approach to expand access to quantitative, inquiry-oriented instrumental analysis learning. This approach is especially relevant where routine access to research-grade instrumentation remains limited.