Portable Quantitative Chemical Analysis: Digital Image Colorimetric Detection of Fe(III) with Curcumin Paper

Abstract

Hands-on experiences in analytical chemistry laboratories are essential to improve students' technical skills on handling analytical glassware and instruments, but the coronavirus pandemic in 2020−2021 disrupted such learning activities. Thus, alternative remote activities are required to supplement practical skills. In this work, a new portable experiment to determine the concentration of Fe(III) by digital image colorimetry with curcumin paper is described. This experiment utilized complexation between Fe(III) and curcumin on a paper substrate, which changed from yellow to red-orange. Then, the RGB intensity changes, obtained using smartphones/devices, were plotted against the Fe(III) standard concentration to construct an external standard calibration curve for determining Fe(III) in unknown solutions. Using students' own smartphone/device enhanced their interest, and the portable small-scale experiment kit enabled a remote hands-on experience at their residence (Lab@Home). The experiment had been implemented both in Lab@Home and in-person formats for three semesters with 591 second-year students majoring in chemistry and other sciences, showing a satisfactory self-evaluated outcome (4.27 from 5) and post-test score (81.5%). The proposed experiment is a showcase to introduce modern analytical chemistry through smartphone/device and digital image colorimetry, while enhancing students' skills and interests in analytical chemistry laboratory.

Digital Image Colorimetry Smartphone Determination of Acetaminophen

“…Table shows some examples of the application of the smartphone as a teaching aid in the analytical, forensic, and environmental sciences, principally using the RGB color model; however, other color models and Apps have been attempted. Previous publications in this Journal have highlighted their application for developing the understanding of the science behind analytical systems such as fluidics, kinetics, − spectroscopy and digital color, − and fluorescence, − along with the possibility of undertaking experiments outside of the laboratory at home. − Previously, using such an approach, it has been shown possible to colorimetrically determine a number of different drugs using the camera on a smartphone. − It has been shown possible to determine the concentration of the drug in sample solutions following the construction of a calibration curve. In this student laboratory practical, the possibility of utilizing such an approach for the determination of acetaminophen and its quantification of unknown samples is described.…”