ReDort Galen W.Ewinga Benedict Visiting Distinguished Professor Carleton College Northfield, Minn. Maarten van Swaay Professorof Computer Science Kansas State University Manhattan. Kan.
The subject of instrumentation is of such importance in modern chemistry that teaching about it on both the undergraduate and graduate levels is essential to all disciplines in which chemistry plays a part. This REPORT explores some of the questions and dilemmas facing those who teach the subject and those who establish undergraduate curricula in chemistry. Separate courses in instrumental analysis, as they were developed soon after World War 11, generally paid scant attention to the basic chemistry of analytical procedures. Often only a few commercial instruments, such as pH meters and photoelectric photometers, were available for student use, and much time was spent on the design of home-built apparatus. Other types of instruments, such as spectrographs and polarographs, could be treated only as library research projects. There seemed to be no way to integrate this material with classical analysis. Over the years, as more and more instruments were developed, it be0003-2700/85/0357-385ASO 1.50/0
@ 1985American Chemical Society
came less realistic to maintain artificial harriers between “instrumental” and “noninstrumental” analysis. Nevertheless, this dichotomy has heen perpetuated in many institutions for reasons of expediency. One factor with far-reaching ramifications has been the extensive treatment of certain instrumental techniques in college courses that are not labeled as “analytical.” This trend originated long ago with the study of spectroscopic methods in connection with the elucidation of atomic and molecular structure, as presented in the physical chemistry course. I t has heen accentuated by the reliance of organic chemists on data from absorption spectroscopy, NMR, and mass spectrometry. Thus it has become convenient for curriculum planners to assume that all the necessary information ahout these important techniques is adequately covered in other courses. At first glance, this would seem to be an efficient and satisfactory arrangement, wherein each technique is taught by those most interested in its
application. The danger is. however. that students will he led to take for granted the internal operation of instruments, without adequate appreciation of their limitations. Addition ally, the instructor in organic chemistry may have neither the time nor the interest in the theory of instrumentation to enter into a detailed examination of alternative instrument designs. It seems clear to us that instrumental analysis should always he taught by an analytical chemist. In some institutions an attempt has h e n made to integrate instrumental and classical analytical techniques into a single course, typically under a title such as”Quantitative Chemistry.” The presentation can then he prtrhlem oriented, making use of any apprupriate terhniques, whether classical or instrumental. This has the great advantage of more closely duplicating real-life situations that an analytical chemist is likely to encounter, in whirh he or she must select as well a i implement the method to he used t o solve a problem most effectively. However, this may result in a course that is too long to fit readily into the curriculum. Hence in many schools two separate courses persist. The instrumental seg ment invariahly comes later in the student’s program than the cunventional “quant” course, thus taking advantage of greater preparation in physics and physical chemistry. This rourse may or may not be required of chemistry majors and is seldom taken by hiology or premedical students. Present address: P.O.Box 2573,Las Vegas, N.M. 87701
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The Instrumental analysis course Let us assume, then, that the instrumental aspects of analytical chemistry will be taught in a separate course. What should he included and what omitted? The necessary compromise between breadth and depth presents a knotty problem. Should we he satisfied with a relatively superficial treatment of many types of instrumentation, or would it be preferable to select a few areas and explore them more fully? One possibility that may he attractive to the professor is to treat in considerable detail one or two subjects with which he or she feels most a t home. The hope then is that the general method of approach developed here can readily be adapted to other disciplines. This may, however, give the student a distorted view of the relative importance of various techniques. No matter what approach is adopted, there must be a decision as to the
degree of mathematical and physical detail to be introduced. Should all equations be rigorously derived, or should those of lesser pertinence be taken on faith, with references given to more complete coverage in the literature? For example, Fick's laws of diffusion as applied to polarography can easily be used without theoretical background, but a rigorous derivation of the Ilkovic equation is essential. Few chemistry teachers would attempt to explain in detail the algorithm for the fast Fourier transform or the detailed theory of the Michelson interferometer as necessary background for a discussion of FT-IR. The real question is where to draw the line, and this is a decision that must be left to the professor. He or she will, no doubt, take into account the available textbooks, and there is quite a variety from which to choose. The professor may prefer a text that includes in an encyclopedic manner a great deal of factual and theoretical material, including the derivation of all significant mathematical relations from first principles. Such a text can hardly be covered in toto in a one- or even two-semester course, so that the instructor must specify which chapters or portions of chapters will be included. On the other hand, it is possible to choose a text that presents the framework on which the instructor can hang as much or as little detail as seems desirable, often amplifying the textual material in his or her own field of expertise. The treatment of each type of instrument should stress the flow of information from the chemical domain, via a transducer and suitable electronics and data processing, to a final report in a form that is directly meaningful to the ultimate user. The limitations of each instrument should be presented in a format that permits easy intercomparisons of parameters such as signal-to-noise ratio, sensitivity, achievable limits of detection, and speed of measurement. The laboratory Curriculum planners must decide whether or not to include laboratory sessions specifically tied to instrumentation. Some top-rated institutions do not, relying on a generalized "Advanced Lab" course to include sufficient experience with instruments. If a separate laboratory for instrumental analysis is decided on, a question arises regaiding the desirable degree of involvement of the student in the design of instruments as contrasted with their use only. If only commercial instruments are used, experiments must he specifically designed to acquaint the student with
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the many available modes of operation. A difficulty often encountered with this latter approach is the unavailability of state-of-the-art instruments in purely educational laboratories. In many institutions expensive items are necessarily purchased on research grants and can be used only by participants in the designated research programs. Instruments for teaching laboratories are likely to be old models, donated to the sehool by local industries that see a chance to combine academic goodwill with a sizable tax writeoff. In this respect some small undergraduate colleges may be better off than their large university neighbors; there is a closeness between students and research projects in the smaller institutions that makes modern instruments available to all if they are present anywhere in the department. Lacking such instruments, the instructor should consider the use of computer simulation-programming a computer to produce data that appear to have come from an analytical instrument.
ANALYTICAL CHEMISTRY, VOL. 57, NO.
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On the other hand, a modular approach can be adopted. The student is asked to synthesize working instruments from available parts, such as light sources, monochromators, and detectors, together with a large selection of electronic building blocks and measuring gear. It is obviously impossible to train a student to be a competent mechanic, an up-to-date electronics wizard. an expert in optics, and a polished computer programmer. as well as a good chemist. The ideal is a noble one, but the practice must be more realistic. A good instrumentation curriculum should provide students with enough understanding of the fields of electronics, mechanics, optics, and computer science to allow them to cooperale effectively with experts in those fields. I t is unlikely that a computer scientist will spend the time to learn the details of, for example, NMR.or that an electrical engineer will be familiar with the nonlinear behavior of the impedance of an electrode surface. In contrast, the chemist is invariably confronted with equipment that relies heavily on state-of-the-art electronics, mechanics, and optics. It is therefore incumbent upon chemists to learn enough of the technical fields that they can at least make their wishes known and he able to evaluate with reasonable confidence the tools constructed by their technical friends-to he sure that such tools will fill therequiremenu of their chemical problems. Electronics Over the past 10 years electronics has progressed to the point where the transfer functions of standard and easily used building blocks can be represented by simple mathematical expressions with an accuracy that meets or exceeds that of mont of the sensors found in the laboratory. A good grasp of mathematics will then goa long way toward the implementation of many useful pieces of equipment. Similarly, standard digital function blocks allow the construction of impressive pieces of dedicated logic with only modest understanding of the circuitry inside the individual units. The convenience of standard electronic building blocks has allowed chemistry students to achieve a useful degree of proficiency in their use in a very short time. This apparent succ w , however, comes at the expense of instilling a false sense of competency. A semester of electronics dealing with potentiostats, integrators, temperature controllers, and digital timers is by no means comparable to a curriculum in electrical engineering. The goal of the electronics exposure thus must
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he twofold The student should he convinced that much useful equipment can he created with a very modest amount of circuit design hut must also recognize that such results are possible only because the performance of the building blocks available usually far exceeds a student's needs. The design of equipment that approaches the limit of electronic performance will always require competence far heyond what can he offered in a chemistry curriculum.
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Computer use The place of computers in the chemistry environment has changed just as spectacularly as that of electronics, hut with entirely different consequences. In contrast with most other equipment, computers can accumulate a mass of recorded data for future digestion. Consequently, computer applications tend to he used not only by the designer and programmer, hut also by his or her teammates and successors. This dictates rigid discipline in areas such as program structure and style, data representation, and documentation. Only a few years ago, the primary use of computers in the chemistry lahoratory was for data acquisition. Operating systems would support only a limited set of operations, including storage of data on tape or disks. Inspection and processing of data were almost invariably done in a separate step (off-line) to avoid real-time complications. Consequently the data acquisition could he kept very simple, and any processing of data was effectively shielded from the laboratory environment. The demands on programming skill were correspondingly
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modest, and most students could create programs that satisfied the needs of their own research or course work. Quite often, however, such programs could only he called disposable: They might he useful to the designer, hut they could not he maintained and would invariably contain quirks that precluded their use by others. Recently, however, the cost of computers has gone down, their performance has improved, and the amhitions of the chemists using them have grown correspondingly. Chemists are no longer satisfied with mere data logging: they wish to control their experiments on the basis of the current data stream. In addition, the convenience of data collection has resulted in rapid accumulation of large files of data that can he managed only with the help of computer search tools and other data-handling techniques. These higher ambitions are directly reflected in program complexity, which in turn requires expanded program investment. As a result of these developments, chemists now realize that proper programming style and documentation habits are no longer mere buzzwords used by computer scientists, hut are becoming a necessary discipline for the chemist who uses a computer. Here again, teachers of instrumentation in chemistry must strike a halance. They can introduce enough material in one semester to allow students to create small programs that will meet their immediate needs, but they cannot hope to train programmers or computer scientists in that time. Unless students are warned explicitly, their success in making a computer obey them may give them an inflated sense of their ability. It is only too easy to find lab drawers full of disks and tapes with undecipherable data that were collected without regard for program discipline. There can he no doubt that exposure to computers has a place in the chemistry curriculum. It is also true that those aspects that are specific to the laboratory environment (analogto-digital conversion, experiment synchronization, data representation as x-y plots, and so on) cannot readily he treated in service courses offered by computer science or engineering departments. The limited amount of time available for computers in the chemistry curriculum must he reserved for information that students :annot obtain elsewhere. These might include discussions about interfaces to instruments available in the department and exposure to application software packages that have been developed for such use. The task of instilling good habits of program style and documentation is
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best left to those who have made that their business, namely, the computer scientists. Although many good programmers can be found among chemists, it is unrealistic to expect that such persons will spend their time teaching programming. Such an activity would divert their talents from their primary task, that of teaching and doing research in chemistry. I t can be very beneficial, however, to maintain a link between chemistry and computer science in the form of a faculty or staff member who can serve as an interface between the two disciplines. It is important that this be a permanent position: The usefulness of such a person depends crucially on the development of long-term associations both with the needs of the chemistry department and with developments in computer science.
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Acknowledgment The authors wish to acknowledge with thanks suggestions for this article from Professors Edward H. Piepmeier and Frank A. Settle, Jr.
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ANALYTICAL CHEMISTRY, VOL. 57, NO. 3. MARCH 1985
Calen Ewing (right) receiued his formal schooling a t the College of William ond Mary and the Uniuersity of Chicago. His industrial experience includes work a t the Sterling- Winthrop Research Institute and at Central Scientific Company. His chief interest, howeuer, has been in education. He has taught a t Blackburn and Union Colleges and a t New Mexico Highlands and Seton Hall Uniuersities. Now retired, he continues writing textbooks in analytical instrumentation and electronics. Maarten van Swaay received his education in the Netherlands and a t Princeton Uniuersity. I n 1963, he joined the faculty of Kansas State Uniuersity as an analytical chemist. Over the years, he became progressiuely mare interested in instrumentation and then in computer applications. For the past three years, he has been a full-time member of the Department of Computer Science a t Kansas State, still maintaining ties with his former colleagues in chemistry.
