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ANALYTICAL CHEMISTRY. VOL. 57, NO. 2, FEBRUARY 1985
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Focus
At the Eastern Analytical Symposium (EAS) exhibit held in November in New York City, it was easy to pass by the Croton Technology Inc. (Waltham, Mass.) exhibit booth without more than a deeultory glance at its sole product-a forlorn little instrument in a beiie metal box. But those who tmk the time to chat with one of the enthusiastic young men at Croton’s booth were rewarded with the discovery of a new concept in analytical instrumentation. What Croton wan showing at EM was the XIS, a relatively inexpensive Fourier transform (FT)spectrometerfor the ultraviolet visible (W-visible) region OP the spectrum,presently c o n f i i e d as a liquid chromatography (LC) detector. Most commercial UV-visible spectrometers are dispersive instrumenta in whicb a prism or grating spreads the spectrum out. A narrow band of wavelengths from the p r i m or grating in selected by a spectrometerentrance slit and is then sensed at a detector. The spectrometerscans sequentially through a serien of sucb narrow ban& to cover the complete spectral range, and there is no multiplex (signal-tonoise or snectral emuisition speed) advantag;. In an interferometric system such as Croton’s, the spectral information is encoded by the interferometer, collected simultaneously (instead of sequentially) by the detector, and then decoded back into the frequency or wavelength domain. Because each element in Croton’s photodiode array (PDA) detector looks at all wavelengths in the spectrum at all times, a multiplex advantage is realized. A noninterferometricUV-visible spectrometermanufactured by Hewlett-Packard, plidway in design be. 276A
tween dispersive and interferometric instruments, eliminates sequential wavelength scanniog without the use‘ of an interferometer. Because spectral information is still obtained simultaneously with this system, it provides a multiplex advantage similar to that available with interferometric instruments. whereas the Michelson interferometer (the type most commonly found in scientific instruments) encodes in the time domain, the common-path holographic interferometer that Croton is using encoden the signal in the spatial domain. Developed some decades ago, the common-path holographic interferometer never caught on commerciaUv. The arrival of the photodiode arrey on the scene in the past few years, however, set the stage for its commercial debut, since the PDA maken it poasible to digitally pmcess spatial information in real time directly off the focal plane of a spectrometer, exactly what is needed to collect the data generated by a common-path holographic interferometer. In Groton’s LC/S, a 512-element diode may picks up the spatidly encoded informationand passes it along to a
AN&YTK‘;M CHEMISTRY. VOL. 57, NO. 2, FEBRUARY 1985
computer, whicb Fourier transform the data and converta it into a useful frequency domain spectrum. Why did Croton cbwse to w e a common-path holographic interfemmeter instead of the more well known Michelson interferometer? As electiomagnetic frequencyincreases from infrared (IR)to visible to W, the moving mirror and light source used to generate the spectrum in the Michelson denim have to be positioned with increas&ly critical p k s i o n . A Wvisible Michelson interferometer therefore tends to be expensive. For example, Bomem Inc.’s DA3-serien Micbelson-based FT spectrometerswbicb use dynamic interferometer alienment. sneciallv stabilized lasers. ana aliasingitechnihues to access ’ wavelengths as low as 200 nm-sell for a base price of about $120,000. Aeeordillg to Croton, the LCIS is rapid-up to 20 spectra per second c ~ l lbe acquired with a computer that is suffciently powerful. And the resolution is good-but 1-2 nm across the entire 200-700-nm spedral range. The LC/S interfaces with an EG&C PARC optical multichannelanalyzer that then forwards the data to a labo0003-2700185/0357-276A$01.50l0
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ratory computer in machine-readable form through standard protoools. “The system will work with an IBM PC or an Apple,” Groton vice-president George Barringer explains, “but there are going to be compromises in the amount of data you can manipulate with such a system. On the other hand, it can download into mainframe memory or hard disk through standard data protocols; you can then acquire all the data coming out of the LC/S at a very high rate of spaed and post-process it.” Groton’s interferometric-PDA LC detector will obviously be in competition with the grating-PDA LC detectors currently offered by a number of manufacturers (I),such aa HewlettPackard, LKB, Tracor Northern, and Varian (which plans to introduce its first such product at this month’s Pittabugh Conference in New Orleans). But with grating-PDA LC detectors selling for about $14,000$%,boo (including an aaaoeiated computer) and the LC/S selling for about $25,000 (including an EG&G PARC optical multichannelanalyzer), the LC/S does not represent a price break. According to Barringer, “An interferometer-basedsystem provides resolution and data acquisition speed that some of the other diode array LC detectors do not provide. In the long run, I think the interferometer system is going to win in a head-to-head contest against the dispersive diode array detector on its signal-to-noise merits and on its data processing merits, just as Fourier transform IR is Winning out against dispersive IR.” However, one of Groton’s competitors, who requested anonymity, responded that although Barringer’s claim about bgttar signal-to-noise was “moderately true, it’s skirting the edge in my estimation. He’s comparing a situation [IR] in which detector noise is dominant and transferring that to a system [UV-visible] that is shotnoise-limited.” Groton cannot presently offer the kind of software and service support that some of the larger dispersivePDA spectrometercompanies can offer, but this may change in the future. For example, a number of major instrument manufacturers are currently engaged in cooperative discussions with Groton that may lead to incorporation of the interferometricPDA into their product lines. Groton is currently targeting LC/S at highly automated laboratories that can benefit from the voluminous amount of data generated by interferometric instrumentation or that are called on to analyze a wide variety of 278A
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seemed to have reached a state of complacent maturity. However, the advent of the dispersivePDA specometer in the past couple of years already provided a certain amount of revitalization in this area. Upon hearing about Groton’s new product, another spectroscopist had these thoughts: “Two years ago I said rather categorically that I thought the photodiode array was the end of UVvisible technological development for the next 10 years, that what would happen would be simply improvementa on the photodiode array. These guys come up with new technology and prove me wrong, and I think that’s super. Because what happens in the end is the chemist wins.”
sample typea on a continuing basis. According to Barringer, “This is a g d instrument for a large research center with an analytical services group tied into a central laboratory computer. The analytical ITOUD may be handed a varietyof tasks. LClS a very flexible, very powerful LC detection system that enables you to just plug in and get data without doing a series of preliminary experiments.” At this point Groton’s commonpath holographic interferometric speetrometer is available only as an LC detector, but the company pLans to introduce a stand-alone W-visible spectrometer based on the same principle. At the EAS meeting, analytical instrumentation consultant Nelson Alpert was enthusiastic about the positive effects such a development could have on the UV-visible spectrometry market, which just a few years ago
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Refermce (1) A n d . Chem. 1983.55.836442 A.
S.A.B.
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What is the proper balance between instrumental and chemical aapecta in the training of analytical chemists? How do we incorporate a strong sense of “real world” analytical problems into the curriculum? What do we do about the already overcrowded curriculum? How do we decide which topica should be retained in the curriculumand which shouldn’t?
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‘It is virtually i m m i b l e to find someone to hire for the faculty who has a good background in instrumentation.mm
I These are some of the questions posed by University of Arizona profes-
sor Henry Freiser at the Symposium on Education in Modern Analytical Chemistry, held Oct. 29,1984, in con-
ANALYTICAL CHEMISTRY. VOL. 57, NO. 2. FEBRUARY 1985
junction with the Aaaociation of Off;cial Analytical Chemists (AOAC) meeting in Washington, D.C. Both industry and academia were represented at the symposium. Warren Cnunmett of Dow Chemical, Robert Libby of Norwich Eaton Pharmaceuticals (a Procter & Gamble Company), and Gilbert Sloan of Du Pont represented industry, and Henry Freiser, Richard Ramette of Carleton College, and Fred Lytle of Purdue supplied academic points of view. Severalof the speakers indicated that in addition to technical competence and educational achievement, various personal attributes are important to a successful analytical chemistry career. According to Robert Libby, “a take-charge, can-do attitude, along with the ability to effectively manage one’s project, he an effective team member, and concisely and competently communicate results in writing or orally to diverse audiences” are important attributes of the successful industrial analytical chemist. Strong communications skills are especially important for analytical chemists because, as Gilbert Sloan pointed out, “Almost all analyses and charaderizations are carried out for someone else. The analytical chemist must perceive a problem about a material or system and must then com-
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_municate capabilities and limitations of the appropriate instrumental technique to the client.” Warren Cnunmett reported the findings of a study of 115 analytical chemists at Dow Chemical. This study shows little correlation between job performance and degee level, age, experience, size or type of college or uniiersity attended, or postgraduate work. A direct correlation was found, however, hetween job performance and the intensity of professional activity. “So philosophy,” said Crummett, “appears to me to be &nost as important as technology in predicting the success of an analytical chemist. You ask, ‘How can philwphy be taught?’ Well maybe it c b ’ t he. It seems to grow with people’s experience and understanding of what their role as analytical chemists is. “But there are some thiigs that can be taught,” Crummett added, “the analytical approach, the design of experiments, the certainty of data, appropriate use of statistics, testing of hypotheses, and the quality control of the whole proceea, but especially of equipment. These things can be taught, and this is what is really need-
So philosophy appears to me fo be almost as important as technology in predicting the success of an ’ analytical chemi:
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ed to upgrade analytical chemistry as a science.”
Currlculum recommendations Several recommendations were made for improvements in the undergraduate and graduate curricula. Richard Ramette described his introductory analytical course, which promotes the importance of inorganic chemical reactions, determination of equilibrium constants, and lab operations. “The introductory course can be modern,” Ramette said, “in the sense
that contemporarycase studies may he chosen as illustrations. However, the c o m e must retain its traditional content to acquaint the students with classical techniques and ideas of permanent value.” Libby proposed upgrading the graduate curriculum through an increased emphasis on the chemistry and analysis of surfaces and polymers. He admits that his professional areas naturally bias his views about the graduate curriculum, but these views probably do represent those of many industrial employers. “We are encouraged to nee some graduate’schools strengthening their surface analysis progrms, but frankly we’d like to see a lot more of this. I imagine that other industries dependent on catalysis, and many are, would agree, as would those in the semicondudor technologies, corrosion, paints and coatings, and in other surface-related industries.” The increasing importance of numerical methods and statistics in hotb the undergraduate and graduate CUIricula was cited by eeveral speakers. Both Crummett and Libby mentioned that the statistical evaluation of analytical data is very important in industry. The requirement for precise and
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reliable analytical data, especially in quality assurancelaboratories, nemasitates the incorporation of fundamentab of statistics and numbers theory in analytical curricub. As Libby put it, “We’re good at crunching more numbers, but are the numbers any good?“ Fred Lytle emphasized the importance of instrument design in the graduate curriculum. “I’m talking about somebody saying that this is what we want to do and now we need to build an instrument to do it, and our being able to supply a graduate student who bas not only a solid trainii in classical analytical chemistry, but ala0 has the expertise and the ability to build the instrument on his or her own.” According to Lytle, “It is virtually impossible to find someone to hire for the faculty who has a good background in instrumentation. By and large, the interest now in academic analytical chemistry is moving back toward chemistry.’’ Academic &emists are becoming more chemically oriented and less instrumentally oriented because of the requirements of the academic system. “If your colleagues demand that you be doing more chemis-
try than instrumentation to get tenured, it’s amazing how you do mbre chemistry in order to be tenured. As a result, the curriculumhas been allowed to stagnate. so far as instrumentation is concerned, and I don’t thiik it represents any longer the modern approaches to designing instruments.” Instrument manufacturers are looking for graduates with solid backgrounds not only in instrumentation but also in numerical methods and programming skills. Lytle described a new three-course series in instrumentation that will help to provide such graduates. Programming experience is important because it helps the chemist understand the algorithms in complex instruments and thus provides the student with better maintenance and troubleshooting skills.“Instruments are fast becoming systems, and if we don’t soon start generating PhDs who can work on this kind of equipment, the whole thing is going to collapse,” said Lytle. An interesting situation that results from the new generation of analytical instrument “systems” is the lack of quality assurance of the computer algorithms contained in the instruments. For example, Lytle mentioned
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an algorithm in an instrument from an “extremely famous” manufacturer in which the slope of a line was not determined by a least-squares method, but by a method that “had no statistical basiswhatsoever!” Lytle then asked whether organizations that eatablish standards, such as AOAC and the American Society for Testing and Materials, are going to have to start approving algorithmscontained in new instruments
The overcrowded curriculum Aaauming we accept these recommendations for new and expanded topics that should be included in the professional curricula, how do we fit them all in? The clasaic problem of how to add something without taking something equally important out becomes a prime consideration. According to Lytle, the average time it takes for a hD to graduate.used to be four years, but is now ofteofive years 61 even longer. “We’re going to have to bite the bullet,” he said, “and have more course8 and labs because there’s nothing else to do. We have to add somethii to the curriculum hemuse we have to maintain the f i a l quality.”
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