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

Abstract

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 5point 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.

Hands-on experiences for remotely taught analytical chemistry laboratories

“…Following the workshops, students then constructed their own spectrometers utilizing smartphones as detectors [ 9 ]. Building the spectrometers was a guided inquiry activity [ 11 ] with students required to have some common elements in their instrumental design, such as a 1-cm polystyrene cuvette as the sample holder and a smartphone paired with the ImageJ software [ 15 ] for data collection and processing (the student handout for this activity is provided in the ESM).…”

“…Most of the materials needed to complete the experiment are inexpensive or common laboratory consumablesexcept for the spectrophotometers, which can be prohibitively expensive (currently, $399). Alternative fluorometric and spectrophotometric setups at a fraction of the cost have been experimented with, building on others' work using LED excitation sources, 3D-printed structures, and smartphone cameras, or photoresistors, for detectors [6][7][8][9]; however, these methods were not deployed in remote laboratory learning for Fall 2020.…”

Lab-at-Home: Hands-On Green Analytical Chemistry Laboratory for New Normal Experimentation

“…The diversity of hands-on, at-home laboratories for chemistry and related fields, i.e., analytical chemistry, organic chemistry, inorganic chemistry, biochemistry, general chemistry, and chemical engineering, has been reported [2][3][4][5][6][7][8][9][10]. Since we could not avoid using chemicals in the chemistry laboratory, the chemicals used in the designed handson, at-home laboratories must be safe for students and their family members as well as friendly to the environment, so that those chemicals could be discarded as household waste.…”

Finding the pKa Values of a Double-Range Indicator Thymol Blue in a Remote Learning Activity

“…Digital image capturing devices have successfully been employed in colorimetric measurements of various analytes from metal ions, − organic dyes, ,, and biochemical samples involving proteins and enzymes − (see ref for review). Because of its portability and ubiquity, students can perform colorimetric chemistry experiments at home using a smartphone to create a standard calibration curve and identify the concentration of an unknown .…”

“…Digital image capturing devices have successfully been employed in colorimetric measurements of various analytes from metal ions, − organic dyes, ,, and biochemical samples involving proteins and enzymes − (see ref for review). Because of its portability and ubiquity, students can perform colorimetric chemistry experiments at home using a smartphone to create a standard calibration curve and identify the concentration of an unknown . In addition to quantification of the color intensities, image analyses can also distinguish between different colors, and we would like to take advantage of this ability to teach the concept of chemical equilibria and acid ionization in a remote learning setting.…”