Authentic Performance in the Instrumental Analysis Laboratory: Building a Visible Spectrophotometer Prototype Mark V
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Article pubs.acs.org/jchemeduc Authentic Performance in the Instrumental Analysis Laboratory: Building a Visible Spectrophotometer Prototype Mark V. Wilson† and Erin Wilson*,† Department of Chemistry, Doane College, 1014 Boswell Avenue, Crete, Nebraska 68333, United States *S Supporting Information ABSTRACT: In this work we describe an authentic performance project for Instrumental Analysis in which students designed, built, and tested spectrophotometers made from simple components. The project addressed basic course content such as instrument design principles, UV−vis spectroscopy, and spectroscopic instrument components as well as skills such as evidence-based decision-making, seeking and applying knowledge, teamwork, and breaking down complex problems. Over the course of the seven-week project, students produced unique, functional spectrophotometers with creative designs. Students reported a high level of engagement and learning during the project. Student performance on a UV−vis spectroscopy assessment instrument improved significantly (28%) from a pretest to a post-test, with the greatest gains occurring in items aligned to the project learning outcomes. KEYWORDS: Upper-Division Undergraduate, Analytical Chemistry, Laboratory Instruction, Problem Solving/Decision Making, Collaborative/Cooperative Learning, Inquiry-Based/Discovery Learning, Hands-On Learning/Manipulatives, Instrumental Methods, UV−Vis Spectroscopy odern UV−vis spectroscopy instrumentation continues classrooms from the high school level to the upper-division − M to evolve, becoming more capable, robust, and user- undergraduate level.3 23 The purpose of such instruments is to friendly with each generation. Spectrophotometers are now (1) demystify the “black box” of spectroscopic instrumentation produced that can operate from the UV through the NIR by providing instruments with components that can be seen and wavelength range, read up to eight absorbance units, and achieve manipulated and (2) provide instruments for students to use at a better than 0.05 nm resolution.1,2 These and other advances reduced cost compared to commercially available options. These make UV−vis−NIR spectroscopy, already a widely applied hand-built instruments have varied widely in design from simple − − analysis technique, useful for an expanded range of applications, LED → sample → light detector photometers7 9,11 18 to diode- and therefore even more important for future scientists to array-like cell-phone spectrophotometers,3,19,20 dual beam ff instruments with lock-in detection,10 and scanning instruments understand. Unfortunately, one side e ect of advances in − − spectrophotometer design has been to make the internal incorporating monochromators.4 6,21 23 Likewise, they vary construction and operation of these instruments more of a widely in construction materials from salt shakers and digital “ ” picture frames3 to 3-D printed construction14,17,19 and black box than ever before. There is no longer an easy way to lift − the lid on most instruments to see and explore what is inside sophisticated circuitry.10 12,21,22 without risking damage to an expensive instrument. This trend Hand-built spectrophotometers have largely been presented as has been extended to the software as well. Modern software often short-term projects for instructors or students to build from defaults to settings such as “speed of scan” or “resolution” provided instructions and use to make absorbance or simple 3−14,16 without indicating what instrumental parameters are adjusted kinetics measurements. In a few cases, students were asked with the different options. There is often no direct way to change to perform critical analysis of the performance of specific 15−23 hardware settings such as slit width. User-friendly software also components or the overall instrumental design. In several performs much of the data analysis automatically, particularly for projects, students explored the effects of altering individual common applications such as water quality analysis and protein components of the instrument, such as the light source, grating, 16−19 or DNA/RNA analysis. Thus, improvements in UV−vis or detector, on overall instrument performance. Scheeline instrumentation have made teaching and learning these instru- had students choose important placement parameters for ments in a hands-on way more challenging. instrument components to help them understand the As instruments have become more difficult to examine and fundamental origins of limitations in instrument performance, 20 manipulate directly, do-it-yourself spectrophotometers have such as stray light versus light throughput. Similarly, the become increasingly popular as a way to introduce students to this important instrumental method. A variety of hand-built Received: July 12, 2016 visible single- or multiple-color colorimeters and spectropho- Revised: October 17, 2016 tometers have been reported in the literature for use in Published: November 11, 2016 © 2016 American Chemical Society and Division of Chemical Education, Inc. 44 DOI: 10.1021/acs.jchemed.6b00515 J. Chem. Educ. 2017, 94, 44−51 Journal of Chemical Education Article SpecUP is a spectrophotometer kit that students assemble.22 lecture/discussion course in which the principles and instru- Students choose the placements of different components in the mentation of UV−vis spectroscopy were discussed. Early optical path to optimize the experimental results. iterations of the project were carried out in 2010 and 2012; it Adifferent level of student engagement occurs when students is the 2014 project that we will primarily describe here. design and build instruments themselves. Tavener and Thomas- Spectrophotometer Assignment Oates help students build a photometer and then ask them to 27 According to a recent work by Frey et al., some of the key design and build a working spectrophotometer.21 Likewise, features of an authentic performance assessment are that it is Wang et al. designed a four-week guided inquiry project to realistic and cognitively complex, that it includes formative introduce the principles of spectroscopy and allow students to assessment, that it requires a defense of the final product or design, build, and test a submersible photometer.15 Recently, answer, that it is collaborative, and that multiple measures are Bougot-Robin et al. reported a problem-based learning course in used to evaluate it. In the spectrophotometer project, student which students used materials provided to build and optimize the groups (2−3 students) acted as research and development teams performance of spectrophotometers.23 These projects are for a start-up instrument manufacturer developing an inex- examples of authentic performance tasks, in which students pensive visible spectrophotometer for simple applications. must apply knowledge to a complex task in order to produce a − Students were provided with a range of choices of light sources, tangible product.24 26 The products in these cases are an detectors, dispersion elements, lenses, and mirrors, all necessary optimized instrument and the performance data that demon- circuit components, and multimeters, as well as a range of strate its capabilities. construction materials and a budget of $20. See Table S1 in Authentic performance tasks frame large problems in “real- − Supporting Information for a list of components provided. They world”-like contexts.24 27 Students are responsible for dividing a were given a list of desirable performance characteristics (Table large and complex goal into small subproblems and applying 1). This project is cognitively complex and collaborative, their knowledge to solve them. The outcome of an authentic performance task is a finished product that reflects not only the ’ Table 1. Performance Characteristics for Hand-Built body of knowledge a student has acquired, but also the student s fi ability to transfer and apply that knowledge in context. The final Spectrophotometers Speci ed in the Project Assignment with outcome need not be a single “correct” solution, but can be a Method for Assessing Each Characteristic range of solutions incorporating a diversity of perspectives, Performance Characteristic Assessment Method creativity, and innovation. Authentic assessment tasks directly Adjustable wavelength in visible region Visual, movement of rainbow across address the “Integrative and Applied Learning” learning outcome exit slit for undergraduates published by the Liberal Education and Acquisition of absorbance spectrum of Comparison with spectrum acquired ’ 28 fi chromophore (absorbance characteristics, for same sample using Cary 50 America s Promise (LEAP) initiative in 2007. This is de ned in wavelength calibration) spectrophotometer the report as (ref 15, p 7): Linear absorbance vs concentration response Linear calibration curve of synthesis and advanced accomplishment...demonstrated chromophore through the application of knowledge, skills, and responsi- Reproducible Multiple student-generated bilities to new settings and complex problems. measurements and instructor- generated measurements In the authentic performance task reported here, students User-friendly Instructor measurements using designed and built a visible spectrophotometer, determined its instrument performance and performance limitations, and revised and Detection limit Student determination of detection optimized their design. The emphasis was for students to limit compared to Cary 50 combine a knowledge set gained in classroom study of UV−vis detection limit Linear