REPORT FOR ANALYTICAL CHEMISTS
TRENDS IN THE USE OF SPECTROSCOPIC INSTRUMENTATION A. Lee Smith Dow Corning Corporation Midland, Michigan
This report is the result of a study of a that
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r p H E ADVENT of powerful scientific -*• instrumentation—gas chromatography, infrared, nuclear magnetic resonance, mass spectroscopy— has revolutionized t h e practice of chemistry. T h e effectiveness of the individual chemist has increased manyfold, and he now performs sophisticated research of a t y p e h a r d ly even imagined a generation ago. The revolution has also brought its problems: frustration on the p a r t of the chemist whose employer has not seen fit t o bestow on him t h e blessings of advanced instrumentation ; fears by the expert practitioners t h a t inept newcomers would generate quantities of very expensive and very poor d a t a ; and misgivings on the p a r t of those who are unable or unwilling t o adapt t o change and see the current trend as a threat to their jobs. O p e n Access o r C e n t r a l Services?
T h e problem area t h a t we shall consider arises between t h e first two groups: t h e chemists, whose primary concern is t o perform chemical research or development, and t h e specialists, whose assignment is t o obtain a n d interpret spectroscopic data. Stated briefly, and in the extreme case, the former 26 A
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group holds t h a t spectroscopic instruments are now recognized as essential research tools and, as such, should be used freely by all chemists. T h e latter group insists t h a t meaningful results depend on p r o p er sample preparation, skillful instrument operation, and knowledgeable interpretation of data—proficiencies not possessed b y t h e average chemist. Specifically, then, the problem is: to w h a t degree should nonspccialists have access to these sophisticated and costly instruments? Should the specialist permit access to his instruments by occasional users from outside his area? Should there be any restrictions a t all on who uses the instruments? If so, who sets u p the ground rules for qualification? Should the employer provide open instrument laboratories for the use of all chemists? T h e implications of these questions are more easily recognized when the situation is seen in historical perspective. Development of instrumentation seems to follow a predictable p a t tern. First, a " b r e a d b o a r d " instrument is developed, often by a p h y s icist. Infrared spectroscopy, to choose an example, began with W. W. Coblentz in the period 1 9 0 3 1908 (1). After a 40-year incubation period, during which the potential of the technique was explored by physicists, commercial manufacturers came on the scene in response to a growing demand from chemists. I n the universities, the chemistry faculties became interested in using this powerful tool for probing molecular s t r u c t u r e ; concurrently, their students also became acquainted with its uses. I n industry, the larger chemical and petroleum companies equipped themselves to exploit the new method, and in this environment the analytical potential of the new technique was immediately recognized. Since the first instruments were expensive and delicate, and their operation was complex, t h e y were usually housed in a central location (often the a n a -
lytical laboratory) and operated by a limited few who became experts in their use. Other chemists brought problems to this group for solution (a practice still followed in m a n y organizations). As the breadth of application spread, simpler and more reliable instruments became available and infrared spectroscopy became a common laboratory tool. Also, within the past decade, corporate affluence has made possible the purchase of expensive equipment without extensive justification, whereas in an earlier period, a requisition for, say, a p H meter was carefully scrutinized by top management. T o d a y , well-trained chemists are in short supply but money for new instruments is relatively plentiful, perhaps reflecting in p a r t the great success of the instrumental a p proach to chemistry. I t is logical to conclude t h a t extending the chemist's productivity by furnishing him with a selection of spectroscopic instruments is more t h a n practical —it is almost m a n d a t o r y . According to the practitioners of spectroscopic arts, however, such a viewpoint overlooks several import a n t factors. Although a relatively simple instrument such as a gas chromatograph or benchtop infrared spectrometer can give usable results with a m i n i m u m of operator t r a i n ing, effective operation of the more complex instruments requires months of training and considerable manipulative skill. Such instruments m a y be easily damaged by inept operation. T h e more sophisticated the instrument, the more frequent is the need for maintenance and r e p a i r — m a t t e r s completely beyond the competence of the average chemist. T h e d a t a obtained are complex at best, and spectra should be objectively evaluated and interpreted by experienced and knowledgeable people. I n s t r u m e n t s are, moreover, expensive ; it is obviously impractical to furnish every chemist with a complete set. E v e n with several users, the equipment is
likely to be idle and unproductive a large portion of the time. On the other hand, proponents of open access present the following a r g u m e n t s : T h e chemist himself has a high degree of responsibility for his work and therefore is more careful in collecting and interpreting the d a t a t h a n an analytical chemist. F u r t h e r , he is able t o obtain results immediately, an import a n t consideration in m a n y research projects. T h e n too, more and more research projects are being built around the capabilities of a particular instrument. I n fact, the t r a i n ing of m a n y organic chemists emphasizes spectroscopic characterization of compounds (2, 3) ; spectroscopic work is now considered a major p a r t of his duties. Finally, m a n y chemists have strong do-ityourself inclinations, a t r a i t which is necessarily encouraged in their graduate training. The chemists point to the great success of gas chromatography as an example of w h a t is possible with the open access system. T h e validity of such claims and counterclaims is difficult to assess. T h e picture is clouded also by the emotional overtones involved. There is no denying the fact t h a t in our industrial society, a large, shiny instrument with m a n y dials and meters is an impressive status symbol. More fundamental, however, are the implied t h r e a t s to the specialist: first, t h a t his job is really not necessary and, second, the ego-bruising notion posed by the chemist saying, in effect, " I can do your job as well as you can, and do m y own, too". T h e chemist, for his part, m a y feel seriously frustrated in his research efforts because of delays in processing his samples, poor communications, and an inherent distrust of other people's data. Finally, he m a y ask why he, who has perhaps used an N M R spectrometer in his graduate studies, should be refused the use of a similar instrument in a n industrial laboratory. VOL. 39, NO. 11, SEPTEMBER 1967
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REPORT FOR ANALYTICAL CHEMISTS
Replies to Survey
Table 1.
S u m m i iry of Replies to Questionnaire
N u m b e r o f R e p>Iies
R ο ζ t
_
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The conclusion that may be drawn from these responses is that both systems are workable, but nei ther is free of problems. The open access system is expensive in terms of both instrument costs and chem ist's time; it is difficult if not im possible to accumulate useful com pilations of spectra; and spectro scopic expertise may be lacking ex cept in quite narrow areas. The central services approach, to be suc cessful, must provide rapid or im mediate service and excellent com munication between chemist and specialist—two rather challenging problems. What, then, is to be done? In some cases, an instrument may be simply a fringe benefit, necessary to attract capable people, much the same as paid vacations or retire ment benefits. Clearly, the trend is toward chemistry by instrumenta tion, and almost all newly trained chemists have at least a nodding acquaintance with spectroscopic techniques. But is it possible or practical to make every chemist a spectroscopist also? Perhaps the most workable solu tion to the dilemma is to combine the best features of both approach es. That is, a group of specialists can be maintained to provide rapid, expert service, and to perform spec troscopic research using advanced instrumentation. In addition, small groups of chemists can be equipped with simplified instru ments that are adequate for many of their needs. Infrared and ultra violet "bench top" spectrometers are common in this type of usage; small low-resolution mass spec trometers are becoming available. There is presently a need for a lowcost medium-resolution N M R spec trometer with a minimum of oper ating parameters. The chemist can then use these instruments in a manner best matching his capabili ties and interests; that is, to check the identity and purity of materi als, to follow the progress of reac tions, and to watch for the presence of unexpected functional groups in his product. Matters such as deSee ACS Laboratory Guide for All Products/Sales Office Circle No. 44 on Readers' Service Card
REPORT FOR ANALYTICAL CHEMISTS
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tailed structural analysis, or inter pretation of t h e data in terms of electron density and bond strength are best left t o the specialist. I n the opinion of this author, only the exceptional individual is able to be an expert in both synthetic chemis try and spectroscopy simultaneous ly. There is a great deal to be said for the team approach; the chemist and the spectroscopist both contrib ute the best of their unique talents to the solution of a problem. The competent spectroscopist need have no qualms about the con tinuing need for his services. Fif teen years ago, the specialist was doing routine quantitative and qualitative analyses. T o d a y he is carrying out molecular structure determinations, attacking special ized problems, and devising means of processing spectroscopic d a t a b y computer techniques. I t is entirely possible t h a t in the foreseeable future, the chemist will insert a sample into a prepro grammed infrared spectrometer ; the spectrometer readout will be en tered directly into a computer; the computer will search its file of stan dard spectra and print out the structure of the absorbing species. If a match is not found, the com puter will search a vast file of group frequency correlations, print out the groups present, and perhaps even indicate their most likely ar rangement in the molecule. Similar systems will be developed for N M R and mass spectroscopy, but this technique will be most powerful when all three (or more) types of data are combined by the computer as it focuses on a single problem. Of course, the slogan " G I G O " (garbage in, garbage out) will still hold t r u e ; even the re sources of the computer are no sub stitute for careful sample prepara tion and good operating technique. I t seems certain t h a t in the fu ture, the specialist will spend more of his time teaching, communicat ing, and working with the chemist, accumulating basic chemical and structural information, and devis ing ways of further multiplying the productivity and usefulness of the powerful tools at his command.
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Acknowledgment
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I would like to t h a n k William E . Koerner, Monsanto Company, St. Louis, Missouri; K. L. Shull, The Standard Oil Company (Ohio), Cleveland; J. M . Vandenbelt, P a r k e , Davis and Company, R e search Laboratories, Ann Arbor, Michigan; E l m a Lanterman, BorgWarner Corporation, DesPlaines, Illinois; and D . C. Weiblen, 3M Central Research Laboratories, St. Paul, Minnesota, for permission to quote from their comments. Literature
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α: Û A. Lee Smith received a B.S. in Chem istry from Iowa State University in 1946, and a Ph.D. from Ohio State University in 1950. He joined Dow Corning in 1951 as an infrared spec troscopist in the Analytical Depart ment, and he is now manager of the Spectroscopy Section. Dr. Smith is a member of the American Chemical Society, the Society for Applied Spec troscopy, and the Coblentz Society (past President), and he is Chairman of the ASTM-sponsored Joint Com mittee on Atomic and Molecular Phys ical Data.
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31st EXPOSITION OFCD CHEMICAL INDUSTRIES CÛ
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