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Analytical Chemistry Is Alive and Well At the ACS National Meeting, Allen Bard assesses the state of the art and predicts new directions for the future
"It's really a humbling thing to represent the whole field, especially a field like analytical chemistry, which has so many different parts," said Allen J. Bard at a symposium on Opportunities in Chemistry at the recent American Chemical Society (ACS) National Meeting in Washington, D.C. "It's also a humbling thing to try to project the opportunities in the future. So I hope everyone takes my comments as personal opinion, and not really those of one who is expert in all these areas." Personal opinion though it may have been, Bard's remarks seemed right on the mark as he discussed progress in the field of analytical chemistry since the state of the chemical sciences was last assessed in the
I 1 1 The power at o u r fingertips is huge, but we've only skimmed the surface.
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National Academy of Sciences (NAS) Westheimer report of 1965. An updated report on chemistry is currently being written under NAS auspices by a committee of chemists chaired by George Pimentel of the University of California (Berkeley). Bard is one member of this group, and his presentation at the Opportunities in Chemis-
try symposium afforded a first glimpse of how the analytical chemistry section of the Pimentel report is likely to shape up. A professor at the University of Texas, Bard is also editor of the Journal of the American Chemical Society. How has analytical chemistry progressed since the Westheimer report in 1965? In 1965 there were perhaps 30 000 computers in the world; today, millions of computers are sold each year. This proliferation of computing power has had an enormous impact on analytical chemistry, said Bard. As just one example, the Fourier transform (FT) techniques, such as FT-infrared spectrometry and FT-nuclear magnetic resonance spectrometry, simply would not exist without the computer. Similarly, lasers were just dawning in that earlier period. "The only analytical application I could find for a laser in 1965 was blasting a sample to vaporize it for flame or spark spectroscopy," said Bard. "Now, 17 years later, you see a number of techniques that
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depend on the laser." Surface-enhanced Raman spectrometry (SERS), laser desorption mass spectrometry (LD/MS), and resonance ionization MS (RIMS) are but a few examples. Liquid chromatography (LC) hardly existed in 1965, said Bard. None of the forms of surface analysis—electron spectroscopy for chemical analysis (ESCA), Auger spectroscopy, UV photoelectron spectroscopy, extended X-ray absorption fine structure (EXAFS), etc.—were available at that time. MS was available then, but sophisticated MS techniques like tandem MS (MS/MS), LD/MS, fast atom bombardment (FAB), and secondary ion MS (SIMS) were not. In the field of electrochemistry, ion-selective electrodes and enzyme electrodes had also not yet been developed at the time of the Westheimer report. Now all of these techniques are vital tools of the trade. 0003-2700/83/A351-1316$01.50/0 © 1983 American Chemical Society
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Focus The Westheimer report did address the question of sensitivity. "It said we could measure concentrations at ppm or even sometimes at ppb levels," said Bard. "Now we look at ppt levels or even less. One ppt is the equivalent of finding something a tenth the size of a pinhead on a road from one end of the U.S. to the other. It's an amazing kind of number to think about when you put it in those terms. "But I don't want to leave the im pression that all the problems are solved," said Bard. "I can see a num ber of definite areas where analytical chemistry will have to make advances in the years ahead." Although surface techniques are now very powerful, he explained, they cannot yet handle organic molecules and organic functional groups. "We
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One ppt is the equivalent of finding something a tenth the size of a pinhead on a road from one end of the U.S. to the other.
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can see elements," said Bard, "but we cannot identify the organics. A vast field will emerge if we can figure out ways to look at organic molecules on surfaces. There would also be a huge payoff if we could get some absolute quantitative measurements on sur faces." In addition, Bard explained, surface spectrometers can be used to look at surfaces in high vacuum, but samples under atmospheric pressure or im mersed in liquids are currently inac cessible to surface techniques other than SERS. "There's a good chance we can discover techniques for such samples, given the time and the op portunity," Bard predicted. Other goals to shoot for in surface analysis include higher spatial resolution and improved depth profiling. Analytical chemistry has made huge contributions to biological and medi cal science, "but there are many more to come," said Bard. Real-time meth ods will be developed for instanta neous determinations of substances in the body. Noninvasive analysis, exem plified by whole-body NMR, will be come increasingly important for medi cal studies. Increasing attention will be paid to the analysis of hostile environments and novel media. "As we continue to explore the solar system," Bard pre-
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Allen J. Bard dieted, "we will need more powerful analytical techniques for looking at planets. But we will also need tech niques for the deep sea on Earth. Analysis at the bottom of the ocean is probably as difficult as on the surface of Mars." Bard also sees more and more interest in the analysis of hightemperature, near-, and supercritical fluids. One possible application is monitoring the interior of reactor ves sels of operating nuclear reactors. "Certainly computers and robotics will continue to be important," said Bard. "And we'll design more and more multispecies/multielement probes. One can envision a tiny silicon chip that could probe 20 or 30 ele ments at one time. A probe such as this will be in every car, analyzing ex haust gas and feeding information back to the carburetor. And we may all be monitored with probes so physi cians can continually track our body chemistry."
Analysis at the bottom of the ocean is probably as difficult as on the surface of Mars.
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"The Westheimer report," said Bard, "really neglected analytical chemistry pretty badly." The hope is that this sin of omission will not be re peated in the Pimentel report. "I've had a lot of help," said Bard, "in pre paring the analytical chemistry sec tion of the report." He particularly thanked contributors R. G. Cooks, David Hercules, Fred Lytle, George Morrison, Janet and Robert Osteryoung, and Charles Wilkins. "It's an exciting time in analytical chemistry," Bard concluded. "The power at our fingertips is huge, but we've only skimmed the surface. As time goes on, given the resources and the facilities, we'll do even more."
