Focus
Year of the Robot Robots attract considerable attention at the 1985 Pittsburgh Conference exhibit
This was the year that a number of major instrument companies decided that Zymark had been right all along—that there is indeed a bottleneck at the sample preparation end of analytical chemistry and that this bottleneck represents a market opportunity of major proportions. This was the year that the Pittsburgh Conference was attacked by a marauding horde of robots, flailing their arms wildly about them. Zymark, what hast thou wrought? At the Pittsburgh Conference Centcorn breakfast on Tuesday morning (see related story on p. 658A), the eminently quotable Harold McNair seemed to exemplify what appears to be a growing feeling about sample preparation when he asked, "What would I like?" and then answered his own question: "Automated sample systems. When I have that chicken fat or urine sample, I would like to put that in a simple system, push a button or two, and have that processed. We need that. That's the slowest, most unreliable link in our whole analytical system today." The number of new sample preparation products at this year's show suggests that the analytical instrument manufacturers have already decided to heed McNair's message. Remember the 1982 Pittsburgh Conference, when Zymark Corporation introduced its first lab robot to widespread skepticism about whether it would play in Peoria? Remember 1983 and 1984, when the thought began to dawn on people that the lab robot might actually be a practical device? Well, perhaps 1985 will be remembered for the standing-room-only crowds in front of the Zymark and Perkin-Elmer (PE) robot booths. The lab robot certainly seems to be coming into its own. Yes, PE, one of those billion-dollar companies that are supposedly so big and fat and slow that they can't possi0003-2700/85/0357-651 A$01.50/0 © 1985 American Chemical Society
bly come out with innovative products quickly, is indeed first out of the gate with some serious competition to Zymark's Zymate system. Chemists interested in robotics are already beginning to discuss the relative merits of these two systems. PE's new MasterLab product line, scheduled for shipment in October 1985, is a series of modular units that interfaces to analytical sampling operations and operates in conjunction with a Mitsubishi Model 501 robot arm and electronic drive unit. (The company also introduced a dedicated robotics-type autosampler for its differential scanning calorimeters, but that product is not a fully versatile and reprogrammable robot.) The MasterLab system, like the Zymark Zymate system, is designed to work with scientific instruments from a variety of vendors, although PE is still in the process of writing many of these handshaking routines. One advantage of MasterLab over
the Zymark Zymate, according to Charles H. Lochmiiller of Duke University, who chaired a symposium on robotics at the fall 1983 American Chemical Society national meeting, "is that it has much more humanlike characteristics, such as a fully flexible wrist. For example, it can reach into centrifuges that use slant tubes without any problems. It can bend its wrist, reach in, and take the tube out, which you can't do with a Zymate. And it's a little bit faster." Zymark's Frank Zenie explains that his company purposely decided against the articulating flexible-wrist design that Perkin-Elmer is using because of the greater ease of programming in Zymate's cylindrical coordinate environment and because the additional flexibility of an articulating system was rarely needed, in Zymark's view. "We have six programmable axes of motion available," says Zenie. "The resulting robot motions are well suited to laboratory procedures and have proven to be very efficient and flexible." On the question of speed, although Zenie admits that there are some applications in which it might be nice to have a robot run a little bit faster, he explains that "sample throughput in automated procedures is most often determined by analysis time or other application considerations. Rarely is robot speed the rate-limiting factor, and in many applications it's questionable whether you want the robot to run significantly faster. Zymark, however, is planning to offer an option permitting increased robot speed." Lochmiiller agrees with Zenie's contention that the total speed of analysis is rarely gated by the robot. Lochmiiller also points out that PE's robot has a simple form of tactile sense: "Because there is no feedback on the Zymate's grip, it doesn't know when it has grabbed a tube unless the
ANALYTICAL CHEMISTRY, VOL. 57, NO. 6, MAY 1985 · 651 A
Focus tube is passed through a switch or an optical sensor. With Perkin-Elmer's robot, you can monitor the current that's in the servo that's closing the hand. When it finds a tube, the cur rent will go up. If it doesn't find the tube, there is no increase in current and that can be used for error trap ping." Frank Zenie explains that the Zymate system has had the ability to monitor the current in its servo mo tors all along. "We haven't used it be cause it's another variable for the end user to deal with, but it's in there and it will be implemented as required for future applications." MasterLab is controlled with an IBM PC, the use of which represents a significant policy departure for PE, a company that has been known (and criticized in some quarters) for its ex clusive use of proprietary computer equipment. The company also an nounced IBM-PC compatibility for its UV-visible diode array spectrometer this year and is thought to be consid ering an IBM-PC version of its labora tory information management soft ware system. IBM compatibility does appear to be the way hardware and software products are heading right now, not only in the business office but in the scientific laboratory as well. At the Pittsburgh Conference, PE introduced a number of modules that are designed to operate in conjunction with its robot: a bar code reader for sample identification, test tube racks designed for the robot's grip spacing, a balance interface for automated weighing, a liquid-dispensing module, a vortex mixer, and a vial-sealing sta tion for sample preparation prior to liquid or gas chromatography (LC or GC). P E is currently hard at work on other modules to be introduced later. With its three-year head start in the business, a wide variety of similar modules are already available with the Zymate, and Frank Zenie, who is not one to be upstaged, introduced a num ber of new modules at this year's show as well. Among Zymark's new product intro ductions were the following: two fully automated titration systems, for gen eral-purpose and Karl Fischer mois ture titrations; a new robot hand with high-frequency vibrating capability for powder dispensing; direct GC in terfaces that operate in conjunction with Hewlett-Packard's (HP's) new autoinjector or with a semiautomatic injector from Precision Sampling that fits any gas chromatograph; a software upgrade that provides the Zymate computer with multitasking capabili ty; and a high-speed, hard-wired math
Perkin-Elmer's
new MasterLab
robot
processor that speeds data acquisition and mathematical calculations. Also announced at the meeting was an agreement that will permit HP and its joint venture company, HP Genenchem, to market integrated systems combining Zymark's laboratory robots with various H P scientific instru ments. A somewhat different approach to sample preparation was represented by a new product called AASP (for ad vanced automated sample processor) that Varian Associates is manufactur ing under a license from Analytichem International, a company in which Varian purchased a minority interest last September. The AASP uses spe cial cassettes containing any of 20 dif ferent bonded-silica adsorbents to re tain analytes of interest and elute un wanted matrix materials from analytical samples. The analytes are then injected into an LC column from the AASP's high-pressure cartridge chamber, which is tied into the col umn flow path. According to Varian, the AASP eliminates interferences,
memory effects, and column cleanup and increases analytical throughput— up to 100 samples can be processed automatically. Also introduced by Varian this year was what Varian instrument group president Allen Lauer referred to as "a rather simple robot for our NMR [nu clear magnetic resonance spectrom eter] that does what a human being normally does: It picks up samples and puts them in the magnet. It's very useful for running the instrument overnight." Other entries in this year's robot sweepstakes were Radian, which sells value-added turnkey laboratory robot ics systems based on IBM or Zymark robots, and GCA Corporation, which was showing lab robots adapted from its line of industrial robots. "It ap pears to be a growing trend," says Cleveland State University's Robert Megargle of laboratory robotics, "and we're likely to see much more in the future—many more brands and many more applications." S.A.B.
Small-spot ESCA Debuts at Pittsburgh Conference Electron spectroscopy for chemical analysis (ESCA) is routinely used in industry to characterize polymers, catalysts, and semiconductor surfaces because of its ability to provide chemi cal as well as elemental information. But ESCA has traditionally been a large-area technique with no capabili ty for high lateral spatial resolution. If surface analysis of an area smaller than about one cm2 was needed, an al ternate technique, such as Auger elec tron spectroscopy, was required, and
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information about the chemical state of the surface was difficult to obtain. At this year's Pittsburgh Conference, several new small-area ESCA instru ments were introduced, which will al low analysts to obtain chemical infor mation with enhanced spatial resolu tion. ESCA, also known as X-ray photoelectron spectroscopy or XPS, mea sures the binding energy of electrons photoejected from the surface by soft X-rays. The energies of the emitted
Focus photoelectrons are directly related to the host atoms and their chemical state, so ESCA can provide informa tion on oxidation states, ligand elec tronegativity, and structural effects. Because the inelastic mean free path of an electron in a solid is very short (only a few tens of angstroms), only those photoelectrons originating in the near-surface region will be detected, making ESCA a surface-sensitive technique. There are two ways to achieve small-spot resolution with ESCA— either by focusing the incoming X-ray beam or by limiting the surface area from which photoelectrons are collect ed. Both methods are used in the new ESCA instruments introduced at this year's Pittsburgh Conference, with the major instrument manufacturers dif fering in their opinion as to which method is preferred. Surface Science Laboratories (now a subsidiary of Kevex) chose to focus the incoming X-ray beam when de signing its small-area instrument. SSL introduced its first small-spot ESCA in 1982 and has now expanded it into a range of configurations, including a relatively inexpensive "Top-Hat" model for those who already have the required vacuum system and a model that will accept samples up to 7 in. in diameter. The instruments use an alu minum anode and a quartz crystal to produce monochromatic X-rays that can be focused to a beam diameter of between 150 μπι and 1 mm. According to Donna Bakale of SSL, the mono chromatic X-ray beam eliminates un wanted satellite lines and improves the energy resolution. The total X-ray flux to the sample is lower, however, than that obtained with a convention al X-ray source. Perkin-Elmer's Model 5400, the new small-area addition to the com pany's PHI 5000 series, illuminates a large area of the sample and then uses an externally selectable aperture plate to vary the photoelectron collection area from slightly less than 200 μπι2 to 30 mm 2 . The Model 5400, like all of the 5000 series instruments, has dualanode capacity, which allows the ana lyst to vary the energy of the X-ray beam, and thus the kinetic energy of the emitted photoelectrons. This is useful for varying the effective analyt ical depth because the mean free path of an electron is energy dependent. Dual-anode capability is also used in Auger parameter calculations that en hance the chemical information avail able by comparing the energies of Au ger electrons and photoelectrons and in resolving ESCA peaks from inter fering Auger electron peaks. When a
Surface Science Laboratories' small-spot
ESCA
different energy X-ray is used for exci tation, the photoelectron peaks show a corresponding shift in energy, but the energies of the Auger peaks remain the same. The ESCALAB Mkll system, new from VG Instruments, allows the ana lyst to choose which small-area tech nique is best for his or her particular application. The ESCALAB, also with twin-anode capability, can either fo cus the X-ray beam or use an aperture to achieve resolution of areas as small as 250 μπι in diameter. VG has also in corporated conventional large-area twin-anode ESCA, Auger electron spectroscopy, and secondary ion mass spectrometry into the ESCALAB sys tem. All of these instruments can be used for small-area studies of insulating materials, although this type of analy sis is more complicated with an instru ment that focuses the X-ray beam rather than limiting the photoelectron collection. Because a focused X-ray beam causes photoemission of elec trons from a very small area, charge buildup on the surface can cause charge-induced line broadening. Charge buildup is not much of a prob lem with conducting materials because electrons simply feed in from the sur rounding area, but this "electron feed" can't occur in insulating materials. Charge buildup (and hence line broad ening) can be minimized by uniform X-ray illumination of the entire analy sis area, as is possible with the PerkinElmer and VG instruments. When us ing a monochromatic X-ray beam,
such as that used by the SSL instru ment, an additional electron source is necessary to provide replacement elec trons for those lost in the ESCA pro cess. Although the instrument manufac turers are promoting the small-spot capability of the new ESCA instru ments, Richard Linton of the Univer sity of North Carolina at Chapel Hill points out that "these are becoming high-performance instruments and the small-spot capability is just one of the improvements. Recent instrumen tation has been improved in many areas including electron optical de sign, computer hardware and soft ware, sample-handling capabilities, vacuum components, and X-ray sources." A completely different type of small-spot ESCA, the photoelectron spectromicroscope (PESM), has been developed by D. W. Turner, a physi cist at Oxford University. The PESM, a unique two-dimensional real-time imaging system, uses UV, X-ray, and fast-atom sources to generate photo electrons in an intense magnetic field. The "μ-ESCA," a commercial version of the PESM introduced by Thor Cryogenics at this year's Pittsburgh Conference, can achieve spatial reso lution of 40 μηι with X-rays and 1-2 μπι with UV. According to the company, the instrument has a nearly 100% photoelectron collection efficien cy and a count rate as much as 104 times that of conventional ESCA sys tems. Thor Cryogenics hopes to add ESCA mapping soon—that is, the ca-
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Focus analysis of thin-film optical devices and magnetic media. According to Linton, the develop ment of small-spot ESCA "is a signifi cant advance in that there are some problems that can only be solved by the higher spatial resolution, especial ly when the available sample volume for analysis is severely limited. How ever, until the technique is improved in lateral resolution to at least begin to approach that of the light microscope, many materials problems involving microscopic heterogeneity, such as those involving the chemistry of mate rials of micron dimensions in microe lectronics, polymer, particle, and fiber technologies, will remain inaccessi ble." M.D.W.
pability to obtain images of photoelectrons having a particular energy, the equivalent of the Auger map. How much do you have to pay for small-spot ESCA capability? The new instruments are mainly in the $300,000 range, which isn't much more than the cost of a "traditional" largearea instrument. The photoelectron spectromicroscope, however, is consid erably more expensive—a complete system with X-ray, UV, and fast-atom sources costs about $450,000. Small-spot ESCA should prove use ful for industrial analysis and quality control, especially in the semiconduc tor industry, where it can be used to analyze integrated circuit chips intact. Other industrial applications include
First Commercial Cf-Source Mass Spectrometer of the University of Uppsala, includ ing Bo Sundqvist and Ivan Kamensky. The instrument is available in the Scandinavian area from the manufac turer, Bio-Ion Nordic AB (P.O. Box 15045, S-750 15 Uppsala, Sweden), and Kratos Analytical Instruments of Ramsey, N.J., will market the BIN10K in the U.S. and other countries around the world. Up to now, a small number of active PDMS researchers, such as R.D. Mac-
The first commercial instrument dedicated to Cf-252 plasma desorption mass spectrometry (PDMS), exhibited for the first time at this year's Pitts burgh Conference, should be of signifi cant interest to scientists interested in biomolecular MS. The new Bio-Ion BIN-10K, which combines a plasma desorption ion source with a time-offlight (TOF) mass analyzer, was devel oped by an interdisciplinary group at the Tandem Accelerator Laboratory
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farlane of Texas A&M University, who invented the PDMS technique in the early 1970s (1), Brian Chait and Frank Field of the Rockefeller University, and Henry Fales at the National Insti tutes of Health, has worked exclusive ly with homemade Cf-source instru ments. However, the relatively inex pensive BIN-10K may begin to broaden the market for PDMS spec trometers. The basic instrument sells for around $125,000, and a model with a more powerful computer is available for about $180,000. One of the first BIN-10K's off the assembly line—and, in fact, the very instrument on display at the Pitts burgh Conference—has already been installed at the Johns Hopkins Uni versity School of Medicine. According to Robert J. Cotter of Johns Hopkins, "We are anxious to evaluate its perfor mance for a wide variety of problems, so we have made it available to outside users as a Middle Atlantic Mass Spec trometry (MAMS) facility instru ment." The low cost of the BIN-10K should make it accessible to many biochemis try laboratories that require molecu lar-weight measurements but not nec essarily unit resolution. The only oth er way to obtain high-mass capability is with one of the high-performance, double-focusing mass spectrometers, which are usually in the half-milliondollar price range. However, the high er cost of double-focusing instruments is frequently justified by the higher resolution and better mass accuracy and precision they can provide. The Cf-252 PDMS technique is of particular interest for biomedical studies because of its high-mass capa bility. For example, the tetramer of porcine phospholipase that was re cently observed by Cf-source PDMS (2) is one of the highest masses (ap proximately 56,000 amu) ever detect ed on any type of mass spectrometer. The PDMS technique is based on the simultaneous emission of two collinear fission fragments from a radio active Cf-252 source (Figure 1). A typical pair of fission fragments is ioe T c 22+ a n c j i42 Ba i8+> w i t n energies of 104 and 79 MeV, respectively. One fragment desorbs secondary ions from the sample, while the other ion starts a clock that measures the time it takes the secondary ions to traverse a flight tube. When a secondary ion hits a de tector at the end of the flight tube, the clock is stopped and the flight time re corded. The BIN-10K's time-to-digi tal converter has a multistop feature that makes it possible to acquire data from up to 64 secondary ions arising from each desorption event.
Focus Signals from many such events are integrated into a time spectrum (intensity vs. time); total acquisition time may be anywhere from a matter of minutes up to five or ten hours, depending on sample size and purity and on the type of data system used. Because each measured flight time corresponds to a specific mass, this time spectrum is easily converted into a mass spectrum by a computer. Cf-252 PDMS is both competitive with and complementary to fast atom bombardment (FAB) MS for the determination of high-mass biomolecules. FAB MS, developed by Michael Barber et al. at the University of Manchester Institute of Science and Technology (3), is a variation on secondary ion mass spectrometry (SIMS) in which the sample is desorbed from a liquid (usually glycerol) matrix and neutral atoms are used in place of the usual SIMS primary ions. FAB has been very popular for biomedical analysis because of its high mass capability and its compatibility with high-performance, scanning, double-focusing mass spectrometers as well as other magnetic instruments that were already widely available in
MS laboratories at the time FAB came on the scene. FAB MS features a stronger primary ion current than that available in Cf-252 PDMS, and the glycerol matrix tends to enhance the ionization of some molecules. FAB ion sources are now available from a number of commercial vendors. Because Cf-252 PDMS is not practical with scanning mass spectrometers, its widespread application has had to await the appearance of specialized TOF instrumentation, a gap that the BIN-10K will fill. But there are a number of advantages here as well, including a potential for excellent sensitivity at high mass (based on the high ion transmission of the TOF-type analyzer), and the possible advantages afforded by a "cleaner" sample introduction system—ions originating from FAB's glycerol matrix can occasionally interfere with low-mass analyte ions. S.A.B. References (1) Macfarlane, R. D. Anal. Chem. 1983, 55,1247-64 A. (2) Sundqvist, B. et al. Biomed. Mass Spectrom. 1984,11, 242-57. (3) Barber, Michael et al. Anal. Chem. 1982, 54, 645-57 A.
Major Trends in Analytical Instrumentation At the Pittsburgh Conference Centcom breakfast, speakers assessed the direction of new analytical technology and exhorted instrument vendors to develop a wide range of new products and services "What would I like? I would like some instruments designed with no manuals. You shouldn't have to go back and read 37 pages to turn the system on; it shouldn't be that difficult. You should be able to stand in front of an instrument with reasonable knowledge, push a few buttons, read a simple screen, and operate it. . . . That ain't the case, gentlemen, that ain't the case!" said Harold McNair of Virginia Polytechnic Institute. McNair was taking advantage of a rare opportunity to express his thoughts to a ballroom filled with hundreds of scientific instrument company presidents, chief executives, corporate communications officers, and marketing managers at this year's Pittsburgh Conference Centcom
breakfast. Also on the podium that morning were Ramon M. Barnes of the University of Massachusetts and William E. Baitinger of Purdue. The moderator of the panel was analytical instrumentation consultant Richard A. Dreher of RAD Associates (Cupertino, Calif.). Centcom Ltd., which provides advertising management services for American Chemical Society publications, sponsored the breakfast. "There are three things I need as a customer," said Baitinger when his turn at the podium came around, "and some companies are doing a better job than others in delivering these to me: I want better price/performance ratios on all the equipment I buy. I want software that is easy to use in a language that is easy to understand. I
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want better serviceability, better built-in diagnostics on my equipment, better documentation, and better after-market support." Atomic spectrometry From the standpoint of new instrument sales, dc arc spectrometry and flame emission spectrometry are on the way out, said Ramon Barnes. Dc arc spectrometry, in which sample excitation occurs in the gap between a pair of electrodes, is primarily a qualitative technique with poorer accuracy and precision than the newer plasma emission techniques. Although flame emission is still important, especially for alkali metal determinations in clinical settings, its overall popularity has declined considerably. Barnes says that the most popular atomic spectroscopic instrument today is the inductively coupled plasma-atomic emission spectrometer (ICP-AES), which has reached a mature phase of development. Electrically generated plasma sources that are in competition with the ICP, such as the direct-current plasma (DCP), the glow discharge lamp, and the microwave-induced plasma (MIP), are not doing as well. In the only commercial DCP currently available (manufactured by the SpectraMetrics subsidiary of Beckman Instruments), a Y-shaped plasma is formed between two spectrographic
mmmmmmmmmmmmmmmmmmmmmm • · I want better price/ performance ratios on all the equipment I buy . . . 7 want software that is easy to use... I want better serviceability,... better documentation, and better after-market support % %
carbon anodes and a tungsten cathode. The DCP has not enjoyed the same popularity as ICP because it is more sensitive to interferences. The glow discharge lamp, a "commercially quiescent" technology according to Barnes, is a device in which a discharge is set up in a vacuum containing a small pressure of inert gas. Sample introduction into the plasma discharge is based on sputtering from a solid electrode made up of analyte
Focus material. Barnes insists that "published results from Germany have been very encouraging, but they've been very encouraging for about six or seven years. The market in the U.S. is missing these devices." As a stand-alone emission spectrometer, the MIP has some problems. For example, it has insufficient energy at low power (
