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A New Approach to UNDERGRADUATE ANALYTICAL CHEMISTRY
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any educators have begun to question the methods we use to teach science. They advocate changing our current emphasis on covering a broad spectrum of content to an emphasis on teaching the process of science: how scientists pose questions and seek answers. It is argued that students equipped with strong problem-solving skills will be able to learn the content needed to solve problems they encounter in the future. Having involved significant numbers of undergraduate students in independent student research projects over the past 14 years, I have become convinced that for many students such an experience is the most important educational opportunity they participate in as an undergraduate. The intense involvement in a project in which they must apply content toward solving problems, and in which there is no detailed road map for how to proceed, demonstrates to undergraduate students how science really works. In 1991,1 began to introduce a series of changes aimed at imparting the positive aspects of the research experience into my undergraduate courses in analytical
Thomas J . Wenzel Bates College 470 A
satisfaction with these courses was that the importance of separation methods in chemical analysis was minimized in the introductory course because most texts on quantitative analysis provide only a cursory description of chromatography at the end of the textbook. A more important concern than the order and content of the lecture part of the courses was whether the laboratory experiments adequately represented analytical chemistry. Experiments performed in the chemistry. Although these courses now emphasize the process of analytical chem- introductory course were traditional wet methods of analysis, whereas those peristry, thereby better serving the needs of the students, little in the way of content formed in the advanced course were typical experiments in instrumental analysis. has been sacrificed. In their 1975 textbook, Laitinen and Harris (i) defined the analytical procedure as Previous courses Prior to 1991, two courses,"Introduction to containing five steps: definition of the goal, sampling, separation of the soughtAnalytical Chemistry" and "Instrumental Methods in Analytical Chemistry," were for constituentfromother species present in the sample, measurement of the deoffered. These were rather traditional sired substance, and evaluation and intercourses in quantitative and instrumental pretation of the data. The laboratory exanalysis (see box on p. 473 A), and the periments performed in both courses, but survey nature of the introductory course led to considerable repetition and overlap especially those in the introductory course, almost uniformly focused on the of material between the two. (For exammeasurement and data evaluation steps ple, although the theory of chromatograwhile virtually ignoring the goal-setting, phy was covered in the introductory course, this material had to be repeated in sampling, and separation steps. Unknowns in the introductory course were almost althe advanced course for the presentation of modern chromatographic methods to ways certified samples obtained from commercial sources. have much meaning.) One source of dis-
Analytical Chemistry, August 1, 1995
A group-learning and project-based approach demonstrates how science really works
0003-2700/95/0367 -470A/$09.00/0 © 1995 American Chemical Society
The group-learning approach The two new courses are "Separation Science" and "Analytical Spectroscopy and Electrochemistry" (see box on p. 473 A). Although these courses present basically the same material as the previous courses, the way in which some of the material is covered has been markedly changed to involve a group-learning approach. Gravimetric analysis is not discussed as a specific method, although many of the features are presented in electrochemistry when we cover electrogravimetric methods. There is also no section specifically devoted to titrations, because titrations are performed in our first-year chemistry course and by students in the organic and physical chemistry labs and are also discussed in the classroom units on acid-base chemistry and electrochemistry. A problem with the new format is the lack of a suitable text for an undergraduate course in separation science. Most quantitative analysis texts provide too little coverage of chromatography, and most
instrumental analysis texts do not cover chemical equilibrium in enough detail. I have solved this problem by using a variety of reserve readings in separation science (quantitative analysis books for chemical equilibrium, instrumental books or chapters from physical methods books for chromatography, literature, and review articles) instead of a traditional textbook. For the unit on chemical equilibrium in "Separation Science," which involves approximately one-half of the semester, the class is divided into groups of three or four students who work together for the entire unit. Groups are assigned after collecting information on the students during the first day of class, and attempts are made to balance the groups on the basis of background and interest. Upper-class students with the most experience are assigned to different groups, and each group usually has both chemistry and biochemistry majors. Groups are usually of mixed gender; although I have never felt
certain that this represents the best approach, students, when asked, have consistently expressed a preference for mixedgender groups. Each day the students are given problems to work on within their group. My role is that of facilitator, to move among the groups and offer suggestions, without offering actual answers, that get the students thinking in the right direction. If one student in a group recognizes a concept needed to solve a problem, she or he is to explain it to the remainder of the group. When all groups appreciate a concept or solve the problem, I summarize the finding. Homework problems are assigned on a daily basis, and after students attempt them individually, each group meets to discuss the assignment before coming to the next class. The unit on chromatography also serves to demonstrate aspects of the historical development of science. In this unit, the students must read certain significant papers on the development of chromatography as Analytical Chemistry, August 1, 1995 471 A
Report well as several review articles; these articles are then discussed in class. The most significant change in the courses is in the lab. Instead of weekly experiments, students now undertake semester-long projects in groups of two to three. (The lab groups are purposefully different from the group-learning teams described above.) These longer experiments (see box) also lend themselves to class themes. For example, one year in "Separation Science," the entire class analyzed different constituents of coffee, including volatiles, acid and base/neutral semivolatiles, amino acids, and methyl xanthines. Laboratory groups are given only topical information about their project, and the first responsibility of each group is to meet with me and the science reference librarian to conduct a computerized search of Chemical Abstracts. Based on the results of the search, copies of appropriate articles are obtained and the students are responsible for determining what procedure will be used for proper sampling and pretreatment to isolate the analyte of interest from impurities. I discuss aspects of sampling and pretreatment with the students and approve any procedure before they begin. Frequently they must order some chemicals or assemble an apparatus (e.g., column chromatography or purge-and-trap device) to complete the pretreatment procedure. During the initial weeks of the course, as the groups are gathering the necessary background literature, I work with each group individually to develop an appropriate level of proficiency with their instrument. Once checked out on their instrument, the groups are allowed (and actively encouraged) to work "off hours" in the lab. ("Off hours" constitute any hours other than the afternoon in which the lab is actually scheduled. Students can come in any time I am in the building to perform any activity provided I know that they are in the lab. On evenings and weekends, activities are limited to specified procedures such as running chromatograms and data workup and analyses that I know do not present safety hazards.) During the semester, each student is required to work 30 h in the lab, and group members are encouraged to coordinate activities so that they do not spend all that 472 A
time together. For example, once a group knows how to prepare the standards, it might make sense for only one member of the group to actually prepare them. Each student logs his or her hours in the lab notebook, annotated to show the tasks that have been done (literature search, reading literature, assembling apparatus for sample workup, learning how to operate the instrument, etc.). Each student writes an individual report in the format of an article in Analytical Chemistry at the end of the semester. The members of the group share the data, but the presentation, interpretation, and discussion of the data in the write-up is done individually. A draft of the Introduction and Experimental Section is due about three-fourths of the way through the term. I critique the drafts and meet individually with each student to discuss my comments.
the topics already covered. The most important attribute of group problem solving, however, is the active nature of the learning. Both the students and I gain a clear sense of what each student understands and where each student is confused. The classroom atmosphere is also far more relaxed than when I lectured to them. A lot of talking is going on, the overwhelming majority of which relates to the problems being covered. The group-learning environment also forces students into the role of teacher. Having to explain a concept to another student is an especially effective way to solidify one's understanding of the material and provides each student with more outlets for help and advice. The groups do meet off hours to go over problems, as is "required" in the course, and as a result, I find students spending far more time working on problems than was done in the past. In previous years, it was typical for students to try a problem on their own, almost immediately get stuck, and then turn in blank answer sheets. Now a group member comes to see me before the problem is due and explains where they as a group decided they are confused; I can then assist them in a meaningful way and they can continue working on the problem. The implication of such a group-learning approach is that cooperation, not competition, is the key to success in the course. I make the point to the students that it is best if everyone works together to help each other understand the concepts presented. This year we are also trying a peer review process for thefirsttimein which stuRelying on people to work together in dents will be paired with a partner who is a cooperative manner does run the risk not in their lab group to assess both the that certain groups may be dysfunctional content and writing style of their report. and therefore compromise the learning During the last scheduled lab, we hold an process. I spend a substantial part of the "Analytical Symposium" (complete with first class explaining group learning, depizza, soda, and ice cream), during which scribing my expectations, and stressing each group gives an oral presentation of my availability to discuss problems should their project to the rest of the class. they arise, and I try to monitor the situation so that I can intercede if problems do develop. Although I have not yet had a Pros and cons of the new group that I would consider dysfunctional, format From my perspective, there are many ad- I did have a group that was ignoring my vantages to the new format. The new or- suggestions in class and then not accomplishing much. After I talked individually der of topics provides less repetition of with each member of the group and rematerial between the courses and a more logical and coherent flow to the topics; the stated my expectations and hopes for them, the group was able to turn the situaextra time is used not to introduce more tion around. topics but instead to spend more time on
Analytical Chemistry, August 1, 1995
Cooperation, not competition, is the key to success in the group-learning approach.
A more likely occurrence is a group in which one member does not seem to coop erate with the others. In the occasional case where this has occurred, it has in volved a bright student who seemed to resent having to share his or her insights with other members of the group. These individuals generally stopped participat ing in the off-hour sessions, but the re mainder of the group had enough mem bers to meet and be productive. When using group learning, it has been tempting to try to ensure that everyone fully understands every concept before go ing on to new material, but unfortu nately, one or two students can then slow down the remainder of the class to unac ceptable levels. In those cases, I have made a point of encouraging the stu dent (s) having the problems to see me individually for additional help. In the two years I have used group learning, how ever, I have not had a single student to whom the rudimentary concepts of equi librium seemed beyond reach. All of them are able to start the most complex of problems, and they can usually tell me quite specifically where they are con fused. At times, especially in the first few weeks, progress can seem slow, and it is therefore important for the instructor to be patient when using group learning. The pace does pick up during the second half of the unit on equilibrium, however, be cause the students have a thorough un derstanding of the basics and because far more learning now occurs outside of the classroom than previously. Ifindthat I can then assign a difficult problem and the students can make reasonable progress on their own.
Comparison of old and new courses "Introduction to Analytical Chemistry"
"Separation Science"
Class topics Statistics Gravimetric analysis Volumetric analysis Equilibrium Spectrophotometry Acid-base chemistry Electrochemical methods of analysis Theory of chromatography
Class topics Chemical equilibrium Acid-base Precipitation Complex formation Liquid-liquid extraction Theory of chromatography GC MS LC Electrophoresis
Labs Labs Determination of benzene and toluene in Determination of potassium hydrogen air using GC/MS phthalate Determination of trihalomethanes in Gravimetric analysis of chloride drinking water using GC/MS Determination of chloride by titration Determination of nitrate and sulfate in Determination of water hardness rainwater using ion-exchange Spectrophotometric determination of chromatography with indirect manganese in steel spectrophotometric detection Analysis of iron by potentiometric titration Detection of the amino acid content of Identification of an amino acid vegetables using reversed-phase LC GC with fluorescence detection Determination of caffeine, theobromine, and theophylline in chocolate "Instrumental Methods in Analytical Chemistry"
"Analytical Spectroscopy and Electrochemistry"
Class topics GC LC MS UV-vis IR Raman Fluorescence AA and AE NMR
Class topics NMR IR Raman UV-vis Fluorescence AA and AE Electrochemical cells Ion-selective electrodes Voltammetric methods
Labs Fluorescence of β-naphthol as a function ofpH Determination of chloride, nitrate, and sulfate by ion-exchange chromatography Determination of sodium in water by AES Analysis of gasoline using GC/MS Compound identification by NMR
Labs Determination of PAHs in smoke and charbroiled meats using LC with fluorescence detection Determination of lead in soil as a function of distance from the road Determination of heavy metals in sludges from secondary waste treatment plants
Project-based labs
In the project-based labs, the students gain a more realistic sense of what it means to undertake a chemical analysis. They ap preciate the necessity of searching the lit erature and realize that when several methods of analysis are available, they will have to select the one that is "best" for their needs. They realize how the criteria and demands of the analyst and the partic ular nature of the sample ultimately influ ence the choice of the "best" method. They see that the work-up is different from the instrumental measurement and
that both have different sets of questions and demands. The "open lab" format helps eliminate the notion that science occurs in threehour time blocks, and it is typical for the students to spend far more than the re quired 30 h on their project. For exam ple, of 14 students in last year's class, one worked more than 50 h,fivemore than 40, and only one less than 35. Students have also been willing to work at unusual hours if it would help to enhance their
project. For example, one group went out to a roadside at 6:00 a.m. to obtain an air sample prior to rush hour and compared it to one collected at 9:00 a.m. the same day. Another group heard that rain and lake wa ter on Mt. Washington in nearby New Hampshire had unusually high levels of constituents of acid ran, so they hiked the mountain to obtain samples (although they insisted that the time spent hiking would not count toward the 30-h laboratory re quirement). Analytical Chemistry, August 1, 1995 473 A
Report Sampling is an especially enjoyable part of the lab. We have gone to the local supermarket to purchase oysters (which we later blended into an oyster frappé), to Burger King to order six hamburgers without the buns, and to a local candy shop to purchase chocolate (we managed to purchase enough chocolate for sampling of another type). Students sampling with a pump and Tenax trap on the quad have enjoyed explaining what they were doing to inquisitive passersby, and the group analyzing the amino acid content of coffee, which joked of looking for some shred of nutritional value in coffee, found much higher amino acid levels when they brewed their coffee in 6 M hydrochloric acid: their so-called strong brew. I believe that enjoying the lab is important, and there is no question that both the students and I have more fun with the project-based labs than we did with the previous experiments. Students can have a good feeling about analytical chemistry, without sacrificing the discipline that is needed to perform reliable analytical measurements. The project approach has also generated a level of independence, critical thought, and empowerment that I did not observe in the previous format. By the end of the semester students are quite willing to work independently and make decisions without verifying them with me. Our instruments are spread throughout several rooms in the chemistry building, and I circulate among the groups monitoring their progress and providing assistance as needed. Prior to the project labs, when I had groups working on several instruments, the students always seemed to be sitting and waiting for me to arrive because they were unsure of what to do next and unwilling to proceed without my authorization. During the first year I used the project labs I was surprised to enter a room and find that the students had taken apart their recorder. It was malfunctioning, so they had read the manual, diagnosed the problem, and were proceeding tofixit. This degree of independence has been typical by the second half of the project labs. Although no group has ever completed its project, because there is not enough time in the semester to perform sufficient replications of unknowns or analyze suf474 A
tance of working with other members of a group, budgeting their time, preparing a report that takes the format of a journal article, and presenting their work orally all contribute to a "real-world" aspect of the lab. There is no question that the new format, especially in lab, has a different emphasis than the previous one. One major difference in the lab is that students do not get the repetitive work performing experiments that emphasize proper technique and use of glassware, and for which they are graded on the accuracy and precision of results. Proper use of glassware is still emphasized, however, in the execution of the projects. Standard solutions are prepared using volumetric glassware, and the trace levels required for the projects necessitate serial dilution. The concept of introducing and propagating error becomes especially apparent to the students as they consider how to prepare trace-level standards. Another difference between the two formats is that students in the projectbased labs do not get the chance to operate every piece of equipment in the department. The trade-off becomes one of the relative value of understanding one instrument in great detail versus many instruments superficially. Almost all the instruments need some repair during a project, and students experience using the manual for troubleshooting purposes. I also enexperience at least one day in class when courage them to read the manuals when they know more about the topic than the others. It is obvious that on those days recording data to learn about features that might facilitate the interpretation and they feel like "experts" on the material, presentation of data for their reports or and I make a point of drawing them into the presentation and talking about some of that might make the accumulation of data easier or more automated. Having masthe particulars of their project. tered the operation of one sophisticated All of the groups analyze real samples and do a sufficient number of standards to instrument, such as a GC/MS, gradient HPLC, or ICP spectrophotometer, the stuget reasonable values. They appreciate how difficult and demanding a process it is dents are not timid about approaching a new instrument when required in another to get a reliable analytical number when course. From other projects, and through performing trace analysis and realize that the lecture portion of the courses, they procedures that were originally time appreciate the capabilities of other instruconsuming would become more routine ments that they have not had the chance with repetition. The desire to have some to operate. results to report to the class in the oral presentation also provides a strong motiThe project-based labs use several sovation for the students to put in extra time phisticated, and therefore expensive, on their project. They appreciate how pieces of equipment, the majority of which much work went into the results they got, were obtained through instructional and a sense of pride pervades the class grants from the National Science Foundaduring the oral presentations. The impor- tion. Costs will be incurred in purchas-
ficient numbers of standards to achieve the desired degree of accuracy, all of them have experienced a satisfying sense of accomplishment. I have often encountered students in the lab or lounge explaining their projects to other members of the class or to students who are not even in the class. Many tell me how they had a long phone conversation with their parents describing the particulars of their project. Because each project incorporates basic concepts or techniques that are eventually covered in the lecture part of the courses (usually long after the students are versed on the methods needed for their project), the members of each group
The project approach has generated a level of independence, critical thought, and empowerment not observed in the previous format.
Analytical Chemistry, August 1, 1995
THE INDUSTRY CHOICE. ing chemicals and supplies the first year that each project is undertaken, but once this is done, the costs are comparable to, if not less than, the costs associated with purchasing unknowns and primary stan dards for a quantitative analysis lab or ma terials and supplies for an instrumental analysis lab. Students occasionally request an item that is too expensive to purchase (we built our own purge-and-trap device rather than buy a commercial model for several thousand dollars), and they then appreciate that budgetary constraints sometimes limit our ability to conduct an experiment. Several students who have participated in the new courses have now gone on to at tend graduate school, seek employment in industry, or participate in summer re search at Bates or elsewhere. I have yet to hear a single complaint from them about having an inadequate background in ana lytical chemistry. What I have heard is how much they still remember about their laboratory project and how much they feel it helped them to know what to expect when conducting research or per forming chemical analyses. I am con vinced that a group-learning approach is a particularly effective method for teach ing quantitative topics such as chemical equilibrium, and would urge any skeptics to try it once. The majority of the equipment used in per forming these experiments was obtained through the Instructional Laboratory Improve ment Program of the National Science Founda tion (Gradient Liquid Chromatograph, CSI8551126; Gas Chromatograph/Mass Spectrom eter, CSI-8750027; Inductively Coupled Plasma, DUE-9452296). Reference (1) Laitinen, Η. Α.; Harris, W. E. Chemical Analysis, 2nd éd.; McGraw-Hill: New York, 1975. Thomas J. Wenzel is Professor of Chemistry at Bates College and President-Elect of the Council on Undergraduate Research. He has taught courses in general and analytical chemistry for the past 14 years, and currently carries out research with the aid of undergraduate students in the areas of NMR shift reagents, selective solvents for GC, and lanthanide luminescence detection in LC. Address correspondence about this article to him at Department of Chemistry, Bates College, 5 Andrews Rd., Lewiston, ME 042404092
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Analytical Chemistry, August 1, 1995 475 A
