Analytical and Bioanalytical Chemistry

, Volume 390, Issue 1, pp 71–75

A picture is worth a thousand words: animations and simulations in the teaching of analytical science

Authors

    • Department of ChemistryUniversity of California
ABCs of Teaching Analytical Science

DOI: 10.1007/s00216-007-1753-6

Cite this article as:
Larive, C.K. Anal Bioanal Chem (2008) 390: 71. doi:10.1007/s00216-007-1753-6

The old adage “a picture is worth a thousand words” is certainly apt when one thinks about the role that animations and simulations can take in the teaching of complex concepts related to the analytical sciences. While traditional approaches such as performing chemical demonstrations and removing the covers from instruments to show their inner workings are still useful, the action embodied in computer animations and simulations make them valuable teaching tools. Fortunately for those of us who are not inclined to code our own visualization routines, there are a large number of high quality freely available electronic resources for use by teachers and students. Many excellent resources are available in annotated form through the Analytical Sciences Digital Library, a collection of peer-reviewed electronic resources freely available at http://www.asdlib.org. This topic was also reviewed by Thomas Chasteen in a recent ACS Symposium series [1].

In thinking about this genre of teaching resources, it is useful to distinguish between animations and simulations. Animations are, in essence, cartoons useful for visualizing a concept that is difficult to fully describe in words. A simulation involves entering parameters into a program to simulate experimental results by calculation. Typically, these resources are stand alone items without accompanying descriptions or instructions. In rare cases, electronic resources, such as the excellent NMR e-text by Joseph Hornak, embed animations as part of the text [2]. Also, increasingly, text book publishers include animations or simulations with their text either as an accompanying CD or through website access [3].

My own experience in using animations and simulations in undergraduate analytical chemistry courses is that just giving the students a url and telling them to “check out this website” is not very effective and seems to have about the same impact as admonishing them to “read the book”. Students often need guidance from the instructor to place the animation or simulation into the context of the course. It is also often necessary to provide instructions about what the student needs to do once they have accessed the website. One way to accomplish this is to provide the students with an assignment to carry out using the web resource that includes a description of the specific learning goals that the animation or simulation should reinforce and a brief tutorial on how to use the program. A formalized example of this approach is the Introduction to Data Analysis learning module by David Harvey and William Otto [4]. This learning module provides a tutorial on uncertainty, comparison of data sets, linear regression, and identifying outliers. The tutorial is supplemented with problems that require students to analyze data sets in Excel™ spreadsheets provided with the learning module. Although they are also useful for reinforcing concepts addressed in the lecture, assignments using animations and simulations can make especially effective pre-laboratory exercises that can familiarize students with calculations, manipulations, or instrumentation they will use in their experiments.

The most effective animations are interactive, actively engaging the student rather than simply adding motion to static pictures. For example, a number of interactive animations written by Thomas Greenbowe, Iowa State University, are freely available on the Internet [5]. Although the primary focus of this collection is the introductory chemistry course, many of these animations could also be useful in the teaching of Quantitative Analysis. For example, as shown in Fig. 1, students can perform a potentiometric pH titration choosing either strong or weak acids or bases. The simulation allows the student to follow the titration using both an indicator and pH measurements. An online tutorial available on the same website can be used to guide the student through the exercise, or faculty can devise their own strategies for incorporating the animation into their course. This simulation can be used in lecture to illustrate the differences between titration of a strong or a weak acid, especially in terms of the buffering capacity of the weak acid. It also makes a nice prelab exercise, as the buret, indicator color changes, and pH meter are good pictorial representations of the experimental setup the student will use in the laboratory.
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Fig. 1

A screen shot of an animated potentiometric titration [5]

Animations or simulations are good supplements to lecture discussion and can be especially effective when demonstrations are too cumbersome or lengthy to incorporate into the lecture. As an example, titrations tend to not make very useful lecture demonstrations because they are difficult to see in a large group and are time consuming to perform properly. However, use of an animated titration or “living graph” [3] allows the instructor to efficiently illustrate the key points of a lecture. Living graphs, like those provided by Harris, provide a simple interface for calculating and comparing results graphically. An alternative is to create your own spreadsheet calculations, which has the added advantage of illustrating how useful spreadsheets can be in simulating chemical equilibria. The instructor can propose a problem for the students to calculate; for example, “Calculate the endpoint pM for the titration of 50.00 ml of 0.0500 M Ca2+ with 0.0500 M EDTA at pH 10”. After the students perform the calculation, the instructor can simulate the titration for the class using a spreadsheet. The calculated result can be compared with the result predicted by each student. When the two results disagree, the instructor can work through calculations that explain the equilibrium chemistry involved. In this situation, the students have a better reason to pay attention to the calculation example because a question has been created in their minds “Why wasn’t the outcome the one I predicted?”. The use of spreadsheets also allows the instructor to rapidly change the conditions, simulating, instead, the titration of Mg2+ or Sr2+ or the effects of changing the pH.

In my instrumental analysis course, I like to treat the various analytical techniques as tools in the analytical tool belt and try to guide the students into understanding how to select an appropriate tool to solve the problem at hand. In this approach, students must consider issues such as detection limits, sensitivity, selectivity, and appropriateness of the method for the sample and the analyte. For a given analysis, there may be several analytical methods, each with their own advantages and disadvantages that one might choose. To fully appreciate the merits and limitations of different techniques and to determine in what situations their use is appropriate, students must have at least a rudimentary understanding of how each instrument works. There are several approaches that one can use to explain the functioning of an instrument, ranging from drawing block diagrams and instrument schematics to taking off the cover of an instrument to show the individual components. Illustrating function by showing students the guts of an older instrument seems to work especially well for spectroscopy-based instruments, perhaps because students have had some prior practical experience manipulating light using prisms or gratings. Animations can help to fill the knowledge gap left by static pictures or instrumental components. Professor Thomas Chasteen, Sam Houston State University, has created an impressive list of animations designed to show the functioning of different analytical instruments [6]. For example, several of his animations can be helpful in explaining differences in optical spectroscopy platforms. The QuickTime animation of a tunable monochromator nicely illustrates how white light can be focused using a slit and a mirror onto the surface of a grating to disperse the various colors of light before focusing it through an exit slit to pass a single color (blue) through a sample cell and onto a photomultiplier tube [7]. Rotation of the grating selects a different color of light (green). The animation includes an audio explanation provided by the author. This animation has all the components of a textbook diagram, but because the individual components are presented one at a time in a sequential fashion, the student focuses on the function of each component. Once the students have a developed a good understanding of how a monochromator functions, they can move onto more complex instruments, for example, the narrated animation describing the function of a double beam spectrophotometer [8].

It can be more challenging to convey to students the functioning of instruments like a quadrupole mass analyzer, which have little relationship to the students’ previous practical experience. Another of Chasteen’s websites describes the functioning of a GC-MS instrument and can be used to bridge this gap by breaking down the instrument into its components and describing the function of each part [9]. This animation depicts the separation of components on the GC column, formation of ions in an electron beam, acceleration, and focusing of these ions for introduction into the mass analyzer. The different ions are separated by the quadrupole mass analyzer allowing only one type of ion to hit the detector, as shown in Fig. 2. The animation goes on to illustrate the detection of ions by a continuous dynode and to explain how data is collected by scanning the mass analyzer to produce peaks in the TIC and mass spectra for each component. Finally, the animation presents a series of questions and answers that cover basic principles related to GC-MS analyses, allowing it to serve as an effective stand-alone tutorial or as a supplement to instrumental analysis lectures.
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Fig. 2

One part of a GC-MS animation showing how a quadrupole mass analyzer separates different ions [9]

Another good resource for animations is the website of Professor Constantinos Efstathiou at the University of Athens [10]. This website contains a number of educational applets for the instrumental analysis course including deviations from Beer’s law, isotope peaks in mass spectrometry, chromatographic separations, diffusion-controlled electrode processes, basic analog and digital circuits, Fourier analysis and signal filtering, and data analysis methods including application of the Student’s t test, Dixon’s Q test for a single outlier, nonparametric regression, and Simplex optimization. The example shown in Fig. 3 explains and demonstrates the operation of a Craig Countercurrent Chromatography apparatus [11]. I discuss this instrument in my instrumental analysis course as a way of bridging the gap between simple two-phase partition equilibria and separation methods with a very large number of theoretical plates like gas–liquid chromatography. The textbook that we use for instrumental analysis does not mention counter current chromatography, even though it has recently undergone a resurgence in its popularity as a research technique, especially in the field of natural product isolation. This website contains a description, photograph, and the generalized equation for calculating the distribution of a solute between the two liquid phases. The propagation of the solute through several transfer steps is presented as well as the equations for calculating the total fraction of a solute in any tube following some number of transfers. The applet accompanying this webpage (Fig. 3) allows the user to set the distribution ratios for two solutes A and B (differentiated by their color) to follow visually each step in the process of extracting and transferring the solutes to the next tube. When the last tube is reached, the animation calculates the percentage of each solute eluted during each subsequent transfer. This animation can be used by the instructor in lecture to illustrate the way countercurrent chromatography functions or independently by students outside of class as a tutorial. Alternatively, the simulation can provide a way for students to check their calculations for an instructor-designed homework problem.
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Fig. 3

A description and accompanying interactive animation demonstrating separation of two components using a Craig Countercurrent Chromatography apparatus [11]

A nice feature of these web-based resources is that each faculty member does not have to spend the time and energy needed to create their own animations or simulations. Just a few of the available resources have been highlighted in this article; many more are just a mouse click away. As you prepare for your next lecture, think about using resources that can make it more animated and interactive. Hopefully, the experience will be rewarding for both you and your students.

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© Springer-Verlag 2007