An Inquiry-Based In-Person or Remote Laboratory Using Iron Analysis and Paper Microfluidics to Teach Analytical Method Development

Abstract

The process of method development is at the heart of analytical chemistry, yet direct experimental experience with the process is rarely taught in the undergraduate laboratory. We report here an experiment that uses rapid, safe, and inexpensive paper-based microfluidics with cell phone detection in order to facilitate the development of a colorimetric method for the determination of iron with three different derivatizing agents (thiocyanate, 1,10 phenanthroline, or FerroZine). This lab has been developed with an inquiry-based pedagogy where students determine which figures of merit to measure, the order to measure them in, and their own procedures for measuring them. This experiment gives students the opportunity to measure linear range, sensitivity, selectivity, accuracy, precision, limit of detection, and optimal reaction time for each derivatizing agent. Students then compare and contrast the measured figures of merit to make an evaluation of which method is preferred for iron quantitation. The results are variable enough from group to group, and each derivatizing agent has different advantages and disadvantages so that there is no "right" answer. This experiment is very flexible and can be modified to fit into one or two lab periods, be delivered with students working in groups or individually, and be delivered in person or in a remote setting. Student learning was assessed using the Enhancing Learning by Improving Process Skills in STEM (ELIPSS) rubrics for management, critical thinking, and information processing. Students demonstrated growth in many skills and expressed significant appreciation for their own learning.

Mobile App to Quantify pH Strips and Monitor Titrations: Smartphone-Aided Chemical Education and Classroom Demonstrations

“…The solution pH was determined using the Smart Indicator Reader app, while simultaneously, the same titration was performed in the absence of the Universal Indicator, but using the Vernier pH meter. Each group collected a minimum of 12 data points at different increments of NaOH addition (0, 4,8,10,11,12,13,14,15,16,17, and 18 mL) and used the collected results to plot a titration curve (pH vs volume of NaOH added for both methods; Figure 4). These titration curves were subsequently compared with the data from the pH meter and Smart Indicator Reader in order to improve the app calibration if needed.…”

“…However, this approach requires sourcing materials and devoting time to building the apparatus. More recently, app based approaches to titrations and spectroscopies have received an extensive amount of attention and are becoming ubiquitous in chemistry teaching laboratories. − …”

Whey Protein Analysis Using the Lowry Assay and 96-Well-Plate Digital Images Acquired Using Smartphones

“…Normally, colorimetric assays were carried out using spectrophotometers. However, nowadays, digital images obtained using electronic devices such as smartphones and scanners have been widely used instead of spectrophotometers. − For example, Na + , F – , Fe 3+ , − Cu 2+ , , NO 2 – , NO 3 – , tyrosinase, glucose, proteins, ,, food dyes, − reducing compounds, and pharmaceuticals − were quantified using digital images.…”

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.…”