50
YEARS ANALYTICAL CHEMISTRY
Analytical Chemistry: the Journal and the science, the 1950's L. B. Rogers Department of Chemistry University of Georgia Athens, Ga. 30602
I am deeply honored to be here to pay tribute to Larry Hallett and to recognize the 50th anniversary of our JOURNAL, ANALYTICAL CHEMISTRY.
Larry not only has a long list of accomplishments in the science of analytical chemistry but also in his position as its first scientist-editor. T o top it all, he is a true gentleman. T h e younger chemists here today are well aware of the major role played by instrumentation in modern analysis. T o help today's chemists appreciate what happened in t h e 1950's, I should like to go back to the early 1940's and relate some personal experiences. World War II, which ended in 1945, brought many scientific a n d engineering breakthroughs in the course of developing radar, infrared night-vision devices, automatic navigation and fire-control devices, and atomic energy. In fact, to u n d e r s t a n d nuclear fission and to measure it required major advances in the understanding of the chemistry of the fission elements and in methods for their determinations in trace a m o u n t s . As electronic and chemical advances became declassified, they quickly found their way into academia and into industry. My P h D thesis, completed in 1942, dealt with new reagents for the gravimetric and titrimetric determinations of sodium and lithium. (Flame emission photometry was not introduced until the late 1940's.) I went to Stanford University-to teach and do research in modern analysis. T h e University purchased a small p H meter (one of the first with a glass electrode), a conductivity bridge, and a polarograph (the first to be equipped with a strip-chart recorder). Within the next year, a Beckman DU spectrophotometer was purchased. T o the best of my knowledge, I had t h e first strip-chart recorder and the first ultraviolet-visible spectrophotometer at Stanford. T o give you an idea of the characteristics of t h a t recorder, the pen took approximately 45 s to cross the chart and reach a stable value. As a result, for a full-scale polarographic wave, I routinely applied a 30-s correction t o the measured half-wave potential. An organic professor, on visiting my lab, cautioned me about getting too interested in the recorder and forgetting to do chemistry. So, any of you who are interested in doing chemistry may wish to discard your recorders! It is instructive to j u m p ahead 26 years to 1968 when I was again in California, this time to learn about on-line
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minicomputers from Jack Frazer a t Lawrence Livermore Laboratory. After one of his chemists got to know me, he drew me aside one day and cautioned me to stay away from online computers or I would never again do any chemistry. Many of my P u r d u e colleagues were of the same persuasion, but, fortunately, I had S a m Péroné a n d Harry P a r d u e on hand to help win t h e m over. Again, be certain t h a t you are not caught with a computerized i n s t r u m e n t if you wish to be considered a " t r u e " chemist.
Instrumentation in the 1950's Between 1942 and 1950 t h e recording potentiometer changed drastically. For our first anodic stripping voltametry, we were able to obtain a Leeds and N o r t h r u p recorder which had a response time of 1.2 s, a sensitivity of 2.5 mV full-scale, and a chart speed of 10 in./min. During the next 10 years, both the full-scale sensitivity and the response speed improved nearly to the levels where they are today. Likewise, oscilloscopes, instead of being 1 V/cm, increased to better t h a n 10 mV/cm. I have listed in Table I other instrum e n t components t h a t greatly aided the analytical chemist during the 1950's. I shall discuss only a few of them. Operational amplifiers, which were the major working units in analog computers, were first made available by Philbrick Associates of Boston. For only $400 one could purchase a low-performance operational amplifier (higher performance, of course, costs more—and then one needed a power supply). Don Deford of N o r t h western University was the first to exploit these, and he designed a versatile electrochemical instrument t h a t he reported a t a national meeting of t h e American Chemical Society in the early 1950's. Electrochemists as a group j u m p e d into this area of electronics because it made possible the high-impedance measurements encountered in working with nonaqueous solutions. In addition, only very tiny currents needed to be passed through the reference electrode. In the hope t h a t he would publish his work, the gentlemen working in electrochemistry referred for many years to his designs b u t never published them. Instead, he became a d e p a r t m e n t head and then a dean! Detectors and sources for various spectroscopic methods also made tremendous strides during this period.
0003-2700/78/A350-1298$01.00/0 © 1978 American Chemical Society
50
YEARS
In addition, note that components for gas-liquid chromatography are on the list. Although gas chromatography was first reported in 1952, it was not until 1954 t h a t it was discussed a t a meeting in this country, the Gordon Conference on Analytical Chemistry. It is important to realize t h a t I use the term gas-liquid chromatography because gas-solid chromatography was used during World War II for analyses relating to control of the butadiene synthetic rubber process. Another item to note is the thermistor which has, because of its great sensitivity, facilitated calorimetric measurements of very small samples and very dilute solutions. Although the transistor appears in the list, it did not reach broad use until the 1960's. T h e last item on the list is the first digital minicomputer intended for laboratory purposes. Its price was onet e n t h or less than t h a t of other computers, so there was a real question as to whether it had a market. T e n years later, the P D P - 1 had developed into the P D P - 8 S , the first digital computer to sell for less than $10 000. Going now to the instruments themselves, we see the nonspectroscopic ones shown in Table II. T h e first item, the single-pan balance, was grudgingly received by many, but it quickly transformed the undergraduate quantitative course. Likewise, the gas-liquid chromatograph started the big revolution in the analyses of volatile materials. Skipping down to the lower end of the list, one finds the automatic analyzer, which has created its own revolution in clinical chemistry laboratories. T h e spectroscopic instruments of the period are listed in Table III. Near the top of the list you will see an automated multichannel emission spectrograph, for use with the arc or spark source. It was widely adopted in the metals industries, especially aluminum (where it started with H. V. Churchill and was carried on by his son Raynor). Another high point to note is the introduction of atomic absorption spectrometry by Walsh of Australia. Finally, the now-ubiquitous proton N M R spectrometer was getting off the ground at 60 M H z and would progress to 100 MHz by the end of the decade. T h e last instrument to be mentioned is the spark source mass spectrometer. This device made possible the analyses of germanium transistor materials for the trace dopants t h a t were added to endow the germanium with its desired properties.
Missing from the list is organic (structural) mass spectrometry only because mass spectrometers were widely used by petroleum companies during World War II to analyze mixtures of hydrocarbons. However, a great advance came about in the 1950's when heated-glass inlet systems and better pumps helped to beat the memory-effects problem t h a t was encountered with polar compounds. Then, the emphasis shifted from quantitative measurements to qualitative measurements relating to the structural information obtained from the fragmentation patterns. In spite of the large number of instruments found in Tables II and III, there were still some techniques t h a t were widely practiced but required no special instrument; or to state it another way, there was no commercially available instrument on the market (Table IV). I shall start with solid electrode voltammetry, for which conventional polarographs were first used but then abandoned or modified to scan much faster. Although Herb Laitinen published his thesis with Kolthoff in 1941, his procedure was a tedious, manual one. During the 1950's electrode materials other than platinum were explored, especially graphite, carbon paste, and a mercury drop or electrodeposited film. Although the early measurements were made using a very slow scan to approach as closely as possible a steady-state value, later a faster sweep not only provided more reliable information but also gave kinetic parameters. Anodic stripping voltammetry is now a widely used technique for determinations of trace materials. It took nearly 20 years for commercially available equipment to be made. Kinetic analysis started with earlier papers by Kolthoff and Livingston and by Kolthoff and Lee. In the first case the catalytic effect of a trace element was determined in much the same way t h a t enzymes are today. In the second paper a mixture of reacting compounds was determined by following the amount reacted as a function of time. In the 1950's Sidney Siggia was engaged in studies along the lines of those taken by Lee, but it was really not until the 1960's t h a t reaction-rate methods became widely studied. Finally, it is important to note that radioimmunoassay was first reported at the end of this decade. It is now widely used in biological and clinical chemistry.
Table I. Components of Instruments Sensitive, fast strip-chart recorders (and oscilloscopes) Operational amplifiers Extended-range photomultipliers for UVVIS Sensitive IR detectors Detectors for counting radioactivity (gas, liquid, solid) Ionization detectors for gas chromatography Capillary columns for gas chromatography Stable, sensitive electrometers Sources for spectroscopy, including AA Thermistor (and transistor) Syringe pumps and minipumps Magnetic stirrers First digital minicomputer for lab (>$100 000)
Table II. Instruments— Nonspectroscopic Single-pan balance Gas-liquid chromatograph High-frequency titrimeter Potentiostat (electronic, high current, fas response) Coulometric titrator Automatic potentiometric titrators Thermometric (enthalpimetric) titrator Thermogravimetric balance (with recorder) Automatic analyzer (for discrete samples) Automated multitube liquid-liquid extractor Vapor pressure osmometer
Table III. Instruments— Spectroscopic Recording UV-VIS and IR spectrometei ers (bench-top) Multichannel analyzers (radioactivity) Multichannel emission spectrometer Atomic emission and absorption spectrometers Spark source mass spectrometer Nuclear magnetic resonance spectrometer Spectrofluorimeter Electron microprobe Spectropolarimeter Electron paramagnetic resonance spectrometer
ANALYTICAL CHEMISTRY, VOL. 50, NO. 14, DECEMBER 1978 · 1299 A
Chemistry Table IV. Techniques Without Unique Instruments Voltammetry, solid electrodes: Pt, Au, C; drop or film: Hg; carbon paste electrodes Anodic stripping voltammetry Chronopotentiometry Photometric titrations Kinetic analysis (reaction rates) Fusion analysis (microscopy) Radioimmunoassay
Table V. Chemicals of Special Analytical Interest Radiotracers: inorganic and organic Ion exchange resins: many functional groups High-boiling liquids for GC columns Inert column packings for GC Molecular sieves: synthetic zeolites Porous Vycor glass Metal hydrides Chelating agents: EDTA relatives; polyamines
Table VI. Analytical Chemistry—The Reactions Titrlmetry: visual or electrochemical indicator Nonaqueous: acid-base, redox Chelometric and complexometric Quantitative organic functional groups General Karl Fischer reagent Kinetic (nonequilibrium) methods Separations General chromatography Homogeneous generation of reagent Organic reagents Liquid-liquid extraction Electrodes Kinetics and mechanisms Extending the sensitivity Trace methods Micromethods—especially elemental analyses of organic compounds
Table VII. Teaching New topics Instruments and instrumentation Quantitative organic functional groups Statistics and experimental design Separations, especially chromatography Kinetic methods Problems More material to cover Less time allowed in curricula Solutions Integrate with other courses Be more selective
Table V is a list of chemical products that were of special analytical interest. Although, for example, ion-exchange resins had been synthesized first in 1935, it was during the 1950's that many types of functional groups were added to the repertoire. In addition, the resins were more stable and did not bleed significantly under most circumstances. At the same time the particles were more nearly uniform in size and were spherical instead of rough. Although porous glass looks like an unspectacular material, it made lowflow salt bridges possible for electrochemical studies. It quickly replaced the agar salt bridge, which was a nuisance to prepare and often failed to gel in the presence of high concentrations of certain salts or solvents. The metal hydrides, especially lithium aluminum hydride, proved to be valuable titrants for nonaqueous acidbase reactions. Similarly, ethylenediaminetetraacetic acid (EDTA) and its many relatives, and also the polyamines, were very versatile titrants for metal ions. The role of titrants is emphasized in Table VI where chelometric and complexometric titrations are again mentioned. In addition, nonaqueous titrimetry, especially acid-base reactions, were very widely studied. Although redox reactions were examined in a limited way, they never did find many applications. The 1950's were the decade of quantitative organic functional group determination. Sidney Siggia, working first with Larry Hallett at General Aniline and Film and later at Olin, was one of the leaders in this field. John Mitchell and Don Smith of Du Pont published an enlarged treatise in which the Karl Fischer reagent for water was used to determine almost every imaginable organic functional group. One of the major efforts was in the study of analytical separations, especially in the area of chromatography. However, liquid-liquid extraction carried out in a Craig machine was very widely applied, particularly in industry. Gravimetry was still receiving attention both in studies of compounds that could be decomposed in solution to produce a precipitating agent and in compounds that could be used for quantitative precipitation or liquidliquid extraction. Lastly, polarography and related
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electrometric techniques exploded during that decade to the point where a large fraction of the academic analytical chemists were doing nothing else. In addition to straightforward determinations of species, much attention was given to kinetics and mechanisms of reactions. Finally, trace methods of analysis and micromethods, especially those directed toward elemental analyses of organic compounds, were developing steadily. The direct determination of oxygen in organic compounds by the Unterzaucher method and the combustion of samples in an oxygen-filled flask (Schôniger) were introduced. In addition, much effort was also devoted to standardization of equipment designs and analytical procedures for well-established elements such as carbon, hydrogen, nitrogen, sulfur, and the halogens. The ion that gave the most trouble was fluoride, which was sensitive to small amounts of metal ions, even the alkali group. Teaching During the 1950's, new instruments and new reactions were coming out so quickly that they posed real difficulties for the teacher at both the undergraduate and graduate levels. That quantitative reactions of organic functional groups should be included in the undergraduate "quant" course as well as inorganic determinations also became clear. Furthermore, the role of analytical separations had been greatly expanded beyond gravimetric methods and liquid-liquid extraction: The undergraduate chemist should become familiar with quantitative chromatographic procedures. It also became clear that kinetic methods should be considered as well as those based upon equilibria. Finally, the analytical chemist was awakening to the need for a better knowledge of smallnumber statistics and experimental design. Like all of the other academic chemists, analytical chemists found that they had enormously more material to cover than they were allowed time for in the curriculum (Table VII). Unlike the organic and physical chemists, the analytical chemists found that the time allowed for their courses was being reduced severely, sometimes to zero. As Professor N. H. Furman pointed out to the writer, academic analytical chemists have rarely represented more than 5% of the total. On the other hand, organic chemists constituted about 50% of the total, physi-
cal chemists about 35%, and inorganic chemists about 10%. Hence, in any democratic discussion of curricula, one could not expect the analytical chem ists to win. As a result, integration of analytical courses into physical or or ganic courses was widely adopted, and the analytical often disappeared en tirely. In situations where analytical courses were allowed to survive at a reduced level, the effect was benefi cial. It forced the teacher of analytical chemistry to be very selective rather than trying to cover "everything." During that period, textbooks in "instrumental analysis" tried to keep up with the rapid changes in instru mentation. (M. G. Mellon liked to say that the buret and balance were "in struments" as far as he could deter mine. In addition, he liked to point out that the analytical balance was ca pable of far higher precision than any other instrument in the laboratory. Therefore, all quantitative methods were "instrumental".) However, most of the "quant" texts were content to stay witb titrimetry and gravimetry— with traces of colorimetry and potentiometric pH titrations (only in water) included. At the advanced level, there was well-rounded activity. Weissberger's multivolume treatise on "Technique of Organic Chemistry", Kolthoff and Elving's "Treatise on Analytical Chemistry", Mitchell's four-volume treatise on organic analysis, and many smaller one- and two-volume treatises on instrumental and chemical ad vances became available including one on the analytical chemistry of the Manhattan Project (atomic energy). It was clearly a time for analytical chemists to adopt a broad approach to the introduction of modern instru ments and modern chemistry to un dergraduates (as well as to graduate students).
Meetings and Associations At the same time that analytical chemistry was having difficulty in academia, it was flourishing in the out side world. The Pittsburgh Confer ence on Analytical Chemistry and Ap plied Spectroscopy, held each year since 1950, continues to be the out standing national analytical meeting. Many new products are introduced each year in the forms of working ex hibits, technical papers, and special seminars for users. Later in the dec ade, chemists active in the Microchemical Society in the New York area joined with other groups to form the
Eastern Analytical Symposium. The emphasis was placed on lengthier re views of subjects rather than short original contributions. Furthermore, a deliberate attempt was made to in vite students as guests. In the Detroit area the Anachem group was formed. Again, although it had academic members, industry was heavily represented. A much less formal group was the Midwestern Universities Analytical Chemistry Conference—MUACC. It is the writer's impression that this was organized by H. H. Willard's former students who liked to get together once a year to discuss informally their research in progress. In spite of the title of the group, college teachers were welcomed and encouraged to participate. During the 1960's, when the writer was in that group, G. Fred erick Smith was a faithful attendee, and he was reported to be a strong supporter not only in spirit but finan cially. In the late 1960's SEACC (in the Southeast) and SWACC (in the Southwest) were started. The JOURNAL
It is a matter of record that Walter J. Murphy, who was editor of INDUS TRIAL AND E N G I N E E R I N G C H E M I S TRY, ANALYTICAL E D I T I O N (which later became ANALYTICAL CHEMIS TRY) was a very strong supporter of the science of analytical chemistry. To compensate for his lack of expertise in that area, he appointed Larry Hallett as the associate editor during his first year in office (1944). Larry, an analytical chemist from the University of Wisconsin, became science editor nine years later (1953) and in 1956 be came editor. One of the high points of each issue from 1946 to 1968 was the column INSTRUMENTATION by Ralph H. Miiller of New York University and later Los Alamos Scientific Laborato ry. His articles covered electronic components, instruments, tech niques—and philosophy. Those who were interested in new or unusual ideas consulted the feature article on instrumentation before reading any thing else. Finally, there was the friendly but firm hand of the editor, Larry Hallett. He encouraged authors to submit basic and theoretical papers to ANA LYTICAL C H E M I S T R Y rather than to other journals. It is a pleasure, Larry, to have the opportunity to thank you for what you did for ANALYTICAL C H E M I S T R Y , both the science and the -JOURNAL.
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ANALYTICAL CHEMISTRY, VOL. 50, NO. 14, DECEMBER 1978 · 1301 A
