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CourseS for Chemistry Majors ROLAND F. HIRSCH Chemistry Department, Seton Hall University, South Orange, N. J . 07079
MY
TOPIC is a general one: analytical chemistry as part of the education of chemists. This topic is of interest today-,beyond the normal reevaluation and rerision that should occur in the teaching of any discipline, because some chemists are questioning whether analysis has any place in academic chemistry and many others see only a minor role for it in comparison with the past. I must admit t h a t I have sornewhat limited experience in the teaching of analytical chemistry. I n my five years a t Seton Hall I have had the opportunity to teach both graduate and undergraduate courses in analytical chemistry. I have taught the basic courses taken by all chemistry majors a t both levels and have been able to make changes in these courses and observe the results. I have concluded t h a t analytical chemistry as presently taught, and as presented in its textbooks, does not reflect the true state or nature of the field. hIy discussion today will try t o focus on the essential aspects of analytical chemistry, for I believe it does have a contribution to chemical education if its real principles are considered. To present my conclusions, this paper has been organized into three parts: first, the reasons for the current low standing of analytical
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chemistry in academic circles, in ternis of the wrong premises which we as analytical chemists have adopted as the bases for our courses : secondly, my views of what the fundamental objectives of analytical chemistry courses should be, and, finally, the outline of a basic course in modern analytical priiiciples. These reinarks are intended to refer to a junior,’senior level undergraduate course for chemistry majors, but there vi11 be iniplications for the basic graduate-level course as well. It is not my intention to infer anything about the specialized courses in analytical chemistry. I must also admit that what I h a r e to say does not give a balanced picture of the situation. Each vieTTpoint has its supporters. and though I may not give the others their due because of limitations of time, I can conceive of valid reasons for disagreeing with what I have to say. What is Wrong?
It is, first of all, a matter of definitions. We can define analytical chemistry as the study of materials to determine their coniposition, usually in chemical, occasionally in physical, terms. V h a t then does one teach as “analytical chemistry?” Well, analytical chemists do certain things in their work.
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They use certain principles in designing their methodologies. These principles are built on the basic laws and theories of chemistry and related fields. It is my belief that in analytical chemistry courses, too much emphasis is placed on --what analytical chemists do -a specific methodology, namely interpretation of spectra -those principles which can be presented in a rigorous manner Let me now explain my objections to each of these in turn. Why shouldn’t analytical chemistry courses for all cheniistry students emphasize “what analytical cheinists do?” Why isn’t it appropriate to deyote most of the arailable lecture time to describing the techniques and methods of our field, and why isn’t it sufficient to use the laboratory to train the students in the skills me use as analytical chemists today? Kell, perhaps the most important objection, as far as I a m concerned, is that this is not teaching the future in lyhich our students will be \Torking. but rather the past and present. Looking back 20 years, just half a professional lifetime ago, can we say that what analytical chemists did then corresponds to what they are doing today? To be sure. some training for the immedi-
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ate future is necessary, but remember that we are not training the future analytical chemists alone, but all types of chemists. The second objection I have is that what analytical chemists do represents a n almost bewildering variety of methods and techniques applied to a tremendous range of types of samples. There isn’t enough time in a college course t o cover all aspects of methodology and applications or even a significant fraction of them, Furthermore, the methods shouldn’t be learned as such anyway, for most of them will be quickly forgotten and can be easily looked up if necessary. This is not t o say t h a t “what analytical chemists do” should be excluded from the basic analytical chemistry courses. Techniques will be covered to some extent, especially in the laboratory. Methods and applications should be used throughout the course as examples, carefully chosen to illustrate principles. Also, the students should be thoroughly acquainted with the sources of reliable methods, such as the AST?vf, APHA. the Treatise on Analytical Chemistry, and the important journals. Lately, courses dealing primarily in the interpretation of the spectra of organic conipounds have become popular. Many institutions offer courses of this type in conjunction with organic and biochemistry courses, usually a t the sophomore level. There is nothing wrong with this type of course-provided it does not represent the main or the only exposure of the chemistry major to analytical chemistry. It is my feeling that this kind of course is going to serve as an excuse for eliminating the independent analytical chemistry course from those required of all chemistry majors a t many institutions. The fact is that the interpretation of spectra type of course misses many key principles of analytical chemistry. It is presented early in the curriculum and has a very limited goal-to teach students how to use an admittedly valuable tool. Being tied to the organic chemistry course, it cannot include a balanced presentation of analytical chem-
istry, even if a few chapters and experiments on titrations and chromatography are thrown in. Another danger I see is that the interpretation of spectra of organic compounds is something t h a t many nonanalytical chemists can do better than most analytical chemists, because it is a tool that they as organic or inorganic chemists make use of constantly regardless of what their specialty may be. To teach interpretation of spectra best, a t most colleges and universities, it therefore should not be the responsibility of an analytical chemist, but rather of someone else who probably isn’t that familiar with current thinking in analytical chemistry. Therefore, if it is conceded that this kind of course is all that every chemistry student need see of analytical chemistry, then the other types of chemists will get the impression that the real anaytical chemist is superfluous since they can teach this better than he can. This is. I feel, a real danger. Academic chemists in general may lose sight of what of analytical chemistry is really fundamental to all chemistry. There must be a distinctive purpose to academic analytical chemistry if it is t o fluorish -indeed, t o survive-in colleges and universities. The analytical chemistry course based on a rigorous development of a limited number of principles is a tradition carried over, in my view, from the earliest days of quantitat i r e chemistry, when close attention to exactness was necessary for advances t o occur in the science. At one time the weight and yolume relationships were the only important chemical laws or generalizations, and they were therefore the most essential part of a chemist’s training. Looking a t the currently arailable analytical chemistry texts, I believe that a disproportionately large amount of space is devoted to gravimetric and rolumetric analyses, usually with but a few chapters on other aspects of the subject added on toward the end of the book. IYow I will agree that the pedagogic value of precision drill in
lecture and laboratory is undeniable, but is it time well spent, considered in light of the overall nature of analytical chemistry? Is it healthy for our discipline to offer upperclass, sophisticated chemistry majors a whole semester consisting of a mixture of principles and ideas which were developed at least 30 years ago, as being the most significant ideas they can learn from us for their future work? The fact is that many if not most analytical problems today are, and tomorrow will be, of a low-precision, ball-park answer, rather than a high-precision type. In clinical analysis, for instance, it is not a question of finding to the nearest tenth of a percent relative the glucose or calcium or albumin content of a patient’s blood. not even to the nearest 1%. Furthermore, many of the most useful analytical principles resist precise quantitation. Even acidbase equilibrium calculations are meaningless beyond two significant figures (maybe even only one significant figure is justified) in practical cases because of activity effects. Putting it another way, we don’t have enough control over our environment-the analytical system-to calculate very many useful things with good precision. Therefore, let’s not emphasize precise calculations and methods (volumetric and gravimetric) in our courses. The students will be introduced t o these concepts in the general chemistry course, where they are naturally a part of the development of atomic and molecular theory. The details of the advanced calculations and methods can be found in reference books and handbooks. The results, say of a complex p H calculation, are best found anyway by experimental measurement, such as by using a p H meter. What Should Be Done?
Having described what I feel is wrong with the teaching of analytical chemistry today, I would like now t o offer a prescription for restoring the vitality of our field as an academic subject. First I will discuss my list of the most impor-
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tant principles of analytical cheinistry; then I xi11 present a n outline for a course which covers them. I beliere that each of the ideas to be enumerated is essential in the education of a cheniist-any kind of chemist. It is niy view, furthermore, that each of these ideas is best presented in the context of the an a lyt i c a 1 ch emist ry course. I n other n-ords, it is through these ideas and concepts that I believe x e as analytical chemists can have an essential role in chemical education. Let me carry this point a little further. Organic and inorganic and biochemists are limited in the types of chemicals and reactions they have to treat and by the theories that are popular today and hence “must be covered.” Physical cheniists today emphasize the niathematical formalisms so that they can keep up Iyith what their peers are doing. General chemistry courses. if they are general, are taught at a point a t which most students have limited kiion.ledge of chemistry. I beliere that the analytical chemist has an opportunity not open to the teachers of the other courses in chemistry. It is an opportunity t o be a generalist, to get to the heart of things chemical, unencumbered by any of the burdens just alloted, perhaps unfairly, t o the others. I recently came across an article that impressed me very much in this regard. I t is called “Strong Inference,’’ by J. R. Platt, and it appeared in Science ill 1964 ( 1 ) . Every chemist, surely every analytical chemist, should read and ponder what Platt has to say about the kind of reasoning mhich leads quickly to important conclusions through the choice of the key experiments. We can teach our subject in a way that will encourage sound reasoning and intuition, rather than the learning of the formalisms, details. theories. and niatliematics which are unnecessary to understanding. Fundamentals of Analytical Chemistry
The first fundamental of analytical chemistry I will call the concept of a signal. There are two types of 44A
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signals, analog and digital, and we should develop an understanding of the characteristics of each. Here I might note that there is some confusion betveen the nature of the signal and of the readout, as is evidenced by the appearence of socalled digital p H meters. I n analysis, the signal must be defined in relation t o two other factors, the background and the noise, and here also I feel t h a t the distinction is not aln-ays made clear in analytical courses. The concept of limit of detection is also part of the idea of a signal. Closely allied with these concepts are the ideas of accuracy and precision, particuIarly the statistical basis for handling experiniental data. I n this regard, I think it is unfortunate that less than half of the currently available analytical texts distinguish bettveen the standard deviation of a method ithat is, of a single result 1 and the standard deviation of the mean, even though most books do define confidence limits, usually as t.s/.\/z> rather than t.s,. The square root law s,,~= s I.\/; is such an important concept in discussing precision of analyses that it should be brought out in analytical chemistry courses right from the start. By the \yay, it has been said that the iiuniber of good scientists is also proportional to the square root of the total number of scientists ( 2 ) . An important point regarding precision is that something is wrong if the experimental precision is much better than that predicted by propagation of errors, as e ell as the more obvious fault in the reverse case. The use of statistical tools as aids to coimmon sense should be stressed in the analytical course. The second fundamental principle of analytical chemistry is t h a t of experimental design. It is true that this is implicit in the discussion of organic synthesis, for example, but the analytical chemistry course is the place where it is developed best in more general terms. There are t v o aspects to experimental design we should cover. First there is the strategj- of research and method development, a
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kind of orerall design to original Iyork. This can be taught with reference t o the many instructire anecdotes in the book by Beveridge, “The Art of Scientific Investigation” 13),which avoids a dry recitation of the stages of the so-called scientific method. A more specific example t h a t I use in discussing experiment design is the Simplex method of optimization of condiLions. The article on this topic by Long ( 4 ) is very helpful. The other kind of experiment design we need to concern ourselves with might better be called method design. Here I refer to the tactics that are employed to be sure that a procedure will actually work when applied to real samples. One should discuss the various types of standardization and perhaps also the use of control charts to check for faulty behavior of a method. L’
The third group of fundaniental concepts of analytical chemistry comes under the heading of instrument design. Here the discussion should center on the electronic, optical, and mechanical components and operations d i i c h can be used to ( a , generate a result, and ( b ) extract this inforniation from the accompanj-ing noise. Some understanding of electronic circuitry and optics is necessary, but I believe a modular approach to instrumentation should be used as much as possible ( 6 ) . Operational amplifiers, for example, can bc discussed in this fashion. The tdliiiques of signal-to-noise ratio enhancement, such as modulation and time-averaging, should be developed as concepts ( 6 ) . Xcxt on my list are the principles of the phenomena of nature which can be quaiitified and hence vhich can be used for analysis. Any property which is descriptive of a chemical system-which aids in specifying a particular system-is appropriately discussed in the analytical course. The treatment should be qualitative for the most part, with a minimum amount of theory and derivation$. The emphasis should be on an understanding of v h a t is going on and how it might be useful in analysis-in
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other words, a practical approach. The theoretical aspect should in the main be presented in the form of useful generalizations such as the Xernst and van Deeniter equations -namely, the theories that really work. Frank ( 7 ) recently noted with regard to the structure of water, “after many years of speculating about what water might be like in order that it display certain properties, we can now begin t o ask what water must be like if certain pieces of data are , . . reliable.” K e in analytical chemistry should be sure t h a t we are teaching the latter type of theory or model. I particularly emphasize the conditional conception of equilibria as developed by Ringbom (8). From the point of view of analytical methods, the idea of side reaction coefficients is a most important concept. All kinds of equilibria can be presented using this approach. The arithmetical similarities among the different equilibrium systems, homogeneous and heterogeneous, can be brought out in this way, avoiding misunderstandings and allon-ing more time t o be spent on the actual chemistry.
I place the ideas of stoichiometry and quantitative relationships last on my list of fundamentals of analytical chemistry not because they are least important. but for the reasons discussed earlier: They are already introduced in general cheniistry courses and they have been o.\-erst-orked in analytical courses. Before presenting the outline of a course which tries to follow these “guidelines,” I would like t o make one final generalization. I think it very important that the analytical course emphasize the interrelationships and similarities betvi-een rarious phenomena. I just mentioned this as an approach t o discussing equilibria; let me no\y give a few other examples of how this can be clone. One good case is that of the steady state. This principle appears over and over in the analytical course, such as in discussing secular, transient, and activation equilibria in nuclear chemistry, chain reactions involving enzymes 46A
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and other catalysts, precipitation from homogeneous solution, and stopped-flow measurements. If a student can understand the kinetics in one of these cases he will have much less trouble Understanding the others if the conceptual similarities are pointed out to him. LikeJTise the electrical plasmas involved in arc and spark spectroscopy, radioisotope decay detectors, and several gas chromatography detectors are based on similar phenomena. The fact t h a t diffusion coefficients increase with temperature has a n effect-not the same alst-ays-on both line widths in atomic spectroscopy and peak widths in chromat ography. A Course Outline for Analytical Chemistry
M y course assumes t h a t the students are juniors or seniors, with a good general chemistry course and some background in organic cheniistry, but no additional physical or inorganic chemistry is necessary as preparation. Probably it would require two semesters t o cover all this material, h single semester would be sufficient if the main goal were to introduce the students to the subject of analytical chemistry with the expectation that they will later go out and learn on their own whatever details they need to know in their work. The first section of the course is devoted to the general features of experimentation-types of errors, statistical tools, experiment design, standardization, presentation of results in the form of tables, graphs and equations, and sampling. There it-ould follow a r e v i m of quantitative concept,s,* volumetric calculations. and equilibria, if necessary. The second section of the course is devoted t o equilibrium principles. Perhaps this should come later in the course, after a discussion of instrumentation, but the laboratory
