770
Anal. Chem. 1981, 53, 770-775
15/17 MeV. Two types of niobium were analyzed, and the results are included in Table IV. Similar to the case of orchard leaves, it was only possible to determine the boron concentration and an upper limit to the concentration of lithium could be given. The results were obtained with respect to the irradiations made a t 15 MeV in one batch (Nb-ES) and 17 MeV in the other (Nb-WCT).
CONCLUSION The method described for distinguishing the contributions to the measured total activity from two elements by performing irradiations with the same particle at two different energies is most successful when the count rates, which depend on concentration and sensitivity, of both the elements are comparable. On the other hand, if they differ by a large factor, as is the case with orchard leaves and niobium, it would be possible then to find the concentration of only one element and estimate an upper limit for the other. In many investigations, such information is sufficient.
ACKNOWLEDGMENT The authors wish to thank H. Schweikert, F. Schulz, and K. H. Assmus of Kernforschungszentrum, Karlsruhe, for providing irradiation facilities and discussions. Thanks are also due to W. G. Faix for several useful suggestions.
LITERATURE CITED (1) Hannay, N. B. “Trace Analysis, Physical Methods”; Wiiey-Interscience: New York, 1965; Chapter 2. (2) Graiiath, E.; Kolblin, G.; Tschopei, P.; Toig, G. I n International Conference on the Analysis of Nonmetals in Metals; Berlin (West), June 1980. (3) Pinta, M. “Modern Methods for Trace Element Analysis”; Ann Arbor Science Publishers: Ann Arbor, MI, 1978. (4) Mapper, D.; Bolus, D. J. J . Radloanal. Chem. 1979, 48, 229-241. (5) Giadney, E. S.;Jurney, E. T.; Curtis, D. 8. Anal. Chem. 1978, 48, 2 139-21 42. (6) McGiniey, J. R.; Schweikert, E. A. Anal. Chem. 1975, 4 7 , 2403-2407.
(7) Oliver. C.; Pelsach, M. J . Radioanal. Chem. 1972, 11, 105-122. (8) Borderie, B.; Basutcu, M.; Barrandon, J. N.; Pinauit, J. T. J . Radloanal. Chem. 1980, 56, 185-198. (9) Albert, Ph. I n “Proceedings, Modern Trends in Activation Analysis”; Coiiege Station, TX, 1961; pp 78-85. (10) Markowitz, S. S.;Mahony, J. D. Anal. Chem. 1982, 3 4 , 329-335. (11) Viaiatte, B. J. Radioanal. Chem. 1971, 8 , 269-276. (12) Dmitriev, P. P.; Krasnov, N. N.; Moiin, G. A.; Panarin, M. V. At. Energ. 1971, 31, 157-159. (13) Krivan, V. Anal. Chem. 1975, 4 7 , 469-478. (14) Krivan, V.; Swindle, D. L.; Schweikert, E. A. Anal. Chem. 1974, 46, 1626-1629. (15) Debrun, J. L.; Barrandon, J. N.; Benaben, P. Anal. Chem. 1978, 48, 167-172. (16) Sastri, C. S.; Petri, H.; Erdtmann, G. Anal. Chem. 1977, 49, 15 10-1513. (I 7) Goethais, P.; Vandecasteeie, C.; Hoste, J. I n International Conference on The Analysis of Non-Metals in Metals; Berlin (West), June 1980. (18) Krivan, V. NBS Spec. Pubi. ( U . S . ) 1978, No. 422, 1189-1214. (19) Engelmann, C.; Cabane, 0. I n Proceedings, Modern Trends in Actlvation Analysis; College Station, TX, 1965; pp 331-338. (20) Ricci, E.; Hahn, R. L. Anal. Chem. 1985, 37, 742-748. (21) Sastri, C. S.; Ney, J.; Moiler, P. Nuci. Instrum. Methods 1979, 159, 369-374. (22) Ishii, K.; Vaiiadon, M.; Debrun, J. L. Nucl. Instrum. Methods 1978, 150, 213-219. (23) Ishii, K.; Vailadon, M.; Sastri, C. S.; Debrun, J. L. Nucl. Instrum. Methods 1978, 153, 503-505. (24) Keiier, K. A.; Munzei, H.; Lange, H. “Q-Values for Nuclear Reactions”; Springer Veriag, Berlin, 1973; Landolt-Bornstein, New Series, Voi. 15, Part a. (25) Petit, J.; Gosset, J.; Engelmann, Ch. J. Radloanal. Chem. 1980, 55, 69-77. (26) Petrov, B. 1.; Degtev, M. I.; Zhivopistsev, V. P. Zh. Anal. Khlm. 1978, 31, 1076-1080. (27) Caietka, R.; Faix, W. G.; Krivan, V., to be submitted for publication. (28) Adam, J. A.; Booth, E.; Strickiand, J. D. H. Anal. Chim. Acta 1952, 6 , 462-47 1. (29) Faris, J. P. Anal. Chem. 1960, 32, 520-522. (30) Kelier, C. Radlochlm. Acta 1983, 1 , 147-156. (31) Ferraro, T. A. Talanta 1989, 16, 669-679. (32) Faix, W. 0.; Mitchei, J. W.; Krivan, V. J. Radloanal. Chem. 1979, 53, 97-106.
RECEIVED for review October 14, 1980. Accepted February 9, 1981. This project was financially supported by Bundesministerium fur Forschung und Technologie, Bonn.
Scanning System for an Echelle Monochromator Donald L. Anderson, Alan R. Forster, and M.
L. Parsons*
Department of Chemistty, Arizona State University, Tempe, Arizona 8528 1
A computer COntrQlled, fully scanning echelle monochromator is described. It consists of three main components. A 0.75-m echelle monochromator has been modlfied to a scannlng system by the addltlon of stepper motors to control the grating and prlsm controls. The control of the stepper motors Is accomplished by a microcomputer. Data are acquired by a seven-channel electrometer and transmitted to a minicomputer system for data storage and reductlon. The instrument has been evaluated with respect to wavelength movement, positionlng, preclsion, resolution, and overall scanning abillty. Wavelength position can be determined with a precision of one step of the stepper motor which corresponds to 0.0001 nm in favorable cases (this depends on spectral order). Transitions as close as 0.01 nm apart can be base-line resolved, and features much closer can be identified. The system performs well and can be used for routlne research oriented spectral information gathering.
Advances in atomic spectroscopy have brought about highly energetic excitation sources such as the inductively coupled plasma (ICP) (I-@, direct current plasma jet (DCP) (9, IO), microwave plasma (11),and improvements in spark sources (22). One of the results of these developments is an increase in number of spectral features emanating from each source, primarily due to increased energy and the resulting increase in ionization. Whenever a large number of spectral features exists, high resolving capability becomes a prerequisite for complete utilization of the information present. Although the requirements for high resolution are many, the conditions can vary from researcher to researcher. In our laboratory, the study of spectral interferences in highly energetic sources such as the ICP and DCP are of prime interest (13,14). Such studies involve the compilation of spectra from many emitting elements both individually and in a matrix. Spectral interferences become more pronounced as the quality
0003-2700/81/0353-0770$01.25/00 1981 American Chemical Society
ANALYTICAL CHEMISTRY, VOL.
r
C
Echelle
Monochromator
Prism Stepper Controller
iyyl Altair 8800a Computer
seven Multichannel
Channel Multiplexed
16K RAM Memory ZK R O M Memory
Electro. meter
Recorder
AED Dual Floppy Disk
Figure 1. System diagram including: (A) microcomputer section; (B)
minicomputer seclion;
(C)
53, NO. 6,
MAY 1981
Table I. Instrument Component Listing Microcomputer Altair 8800a microcomputer with Processor Technology motherboard 16 K Processor Technology Random Access Memory (RAM) 2K Cromemco read only memory (ROM) IMSAI PIC-8 real-time clock and priority interupt control Cromemco D+ 7a seven-channel multiplexed ADC and DAC Percom cassette and RS-232 serial interface Processor Technology 3P+ S parallel and serial 1/0 IMSAI PIO-6 six parallel port interface ASR-33 teletype Minicomputer Digital Equipment Corp. PDP-8/E minocomputer 20K random access memory Advanced Electronics Design 6200LP dual floppy disk system with controller Digital Equipment Corp. communication interface board Spectrometer Spectrametrics Inc. (SMI) echelle grating monochromator Denco SM-2a dual stepper motor controller two RapidSyn stepper motors, Type 34H-509A (1.8" step angle) Jarrell-Ash selected RCAlP28 photomultiplier tube RCA PF1042 photomultiplier power supply Varian 9176 chart recorder
spectrometer seclion.
of resolution decreases, and for that reason, a high-resolution instrument is necessary to distinguish and separate interfering transitions. In many cases the intensity of the emitted spectra may be small enough that important information might be lost in an instrument of low light throughput. The ideal solution would be a monochromator with high resolution coupled with reasonable light throughput. An acceptable solution for these demands exists in an echelle grating monochromator. An echelle grating monochromator uses a large blaze angle, wide groove spacing, and high order number to achieve a high degree of resolution (15). The use of multiple, high order numbers and moderate optical path length ensure reasonable throughput by maximizing the free spectral range in each order (16). The Spectrametrics (SMI) echelle monochromator used in this study offers resolution better than a 3.4-m monochromator (approximately equal to a 6-m conventional monochromator) with light throughput of approximately a 1-m monochromator. This represents an attractive compromise. The echelle system is not without drawbacks. A cross dispersion device must be coupled with the echelle grating to obtain spectra in a more useful two-dimensional format. This has been done and has worked quite well in the SMI system by incorporating a prism as the cross dispersion device with the echelle grating. This system is operated in orders 28-118. To date, this monochromator has been used for single wavelength or direct reader (polychromator) applications. The complexity of the two-dimensional spectral output has slowed development of a full scanning system. In our laboratory, such a monochromator has been modified to provide a full scanning capability. Progress during the past 3 yeare has been discussed a t several conferences (17-19). A description of this instrument and an evaluation of its performance are the focus of this paper.
EXPERIMENTAL SECTION Instrumentation. The echelle system consists of three major components (see Figure 1). The fiist component is a commercially
771
-
Table 11. Multichannel Electrometer Specifications channe1 no.
Ri,
a
1 1.1 x 103 2 1.1 x 103 3 11 x 103 4 11 x 103 5 11 x 103 6 11 X lo3 7 i i x 103
Rf,
a
22 x 106 11 x 106 11 x lo6 1.1 X lo6 iiox 103 11 x 103 1.1 x 103
Cf, pF
full scale current, A
0.05 0.01 0.01 0.005 0.01 0.01 0.1
1.2 X 2.5 X 2.5 x 2.5 X 2.5 x 2.5 X 5.0 x
lo-'' lo-'' 10-9 lo-' 10-7 10-6
available SMI echelle monochromator (see Table I). The monochromator uses a two-dimensional scroll readout for wavelength positioning within hO.1 nm over the entire spectral range. There are coarse and fine controls for the prism and grating. The prism gearing drives a cam which adjusts the prism angle and the grating gearing drives a sine bar which positions the echelle grating. To effect a scanning instrument, the only modification to the monochromator was to replace the fiie controls for both the prism and grating with stainless steel gears. These gears are coupled to gears on two RapidSyn stepper motors (1.8' step angle) with a stainless steel link chain. Chain removal is quick and simple rendering the instrument back to its original state, except with gears instead of knobs on the fine controls. The gear ratios on the prism and grating (prism, 4.881; grating, 2.501) are such that the full range of the DENCO stepper motor controller (65 536 steps) is utilized. The monochromator rests on a 0.5 in. thick aluminum table, 40 X 65 in. The stepper motors are mounted to the table, not to the monochromator, to minimize motor vibration transfer to the monochromator. Light intensity transmitted through the monochromator is measured by a Jarrel-Ash selected RCA 1P28 photomltiplier tube (PMT) operated at -800 V. The signal from the PMT is processed with a seven-range electrometer constructed in our laboratory. to This prototype permits current measurements from 1 X 5 X lo4 A (see Figure 2 and Table 11). The seven channels are multiplexed to a 5-ps analog to digital convertor (ADC). The second major component of the system is an Altair 8800a microcomputer. It is used for real time control of and spectral
772
ANALYTICAL CHEMISTRY, VOL. 53, NO. 6, MAY 1981
V. = - 5 . 0 volts dc regulated All resistances in ohms
additional six channels
Figure 2. Simplified schematic of multichannel electrometer. See Table I1 for component specifications.
acquisition from the monochromator. The computer is equipped with 16 384 bytes of random access memory, 2048 bytes of programmable read only memory, a real time programmable clock with priority interrupts, the multiplexed ADC, modem control, and various input and output channels for the teletype and stepper motors. A communication interface to a PDP 8/E minicomputer is used to buffer spectra for data reduction purposes. The dual stepper motor controller is a DENCO Model SM-2a. It is an intelligent controller in that its only input from the microcomputer is the desired step coordinate for either of the motors. It positions the motor to that location and then flags the computer, allowing the microcomputer the freedom for other control functions while the motors are moving. The CONVERS control language was chosen for programming the microcomputer (20). This is a FORTH-like language (21)that was written specifically for microcomputers. CONVERS is well suited for instrument control type functions. It permits easy incorporation of new components into the echelle system and is very memory efficient. The final component of the system is a Digital Equipment Corp. (DEC) PDP 8/E. The computer has 20480 words of random access memory, a 4800 baud RS-232 interface to the microcomputer and an Advanced Electronics Design dual floppy disk mass storage device. The disk system uses a direct memory access controller and has an unformatted capacity of 739328 bytes. The minicomputer is used for development and storage of all programs for both itself and the microcomputer. DEC OS/8 BASIC is used on the minicomputer for data reduction programs, Control programs written in CONVERS are down loaded into the microcomputer while data reduction programs written in BASIC are run directly on the minicomputer. All spectra taken by the system are stored on disk by spectral order number. The dual minicomputer and microcomputer system was chosen instead of a single computer in order to maximize the efficiency of both computers. The microcomputer is well suited for interfacing and real time data acquisition, while the minicomputer is more convenient for mathematical spectral analysis. Procedure. To a close approximation, the slope of the spectral display of an order has been found to be linear with respect to wavelength. That is, the numer of steps the grating stepper motor moves before the prism stepper motor is moved is essentially a constant within each order. The exact relationship is nonlinear, and so this approximation affects both wavelength positioning and relative intensity of the spectrum. However, this will be the topic of a future investigation. Since slope of the spectral display is a function of order, as is the unit of spectral length per step of the stepper motor, both
Table 111. Order Map Parameters or der 56 starting wavelength, nm 398.00 starting prism coordinate 28354 starting grating coordinate 9712 increment rate, nm/step 0.00020 slope 51 (Fating steps/prism step) ending wavelength, n m 405.00
73 306.00 20611 16450 0.00016 48
254.00 18760 11153 0.00013 46
311.00
258.00
88
must be accounted for when scanning. A system map was developed to define the dependence of slope and spectral length per step with respect to order. This map consists of a starting wavelength, grating and prism positions for this wavelength, slope in terms of grating steps per prism step, and ending wavelength. This information is stored for orders 38 through 118. Orders representing wavelengths above 600 nm have not yet been mapped. The data for the system map were taken by finding the grating and prism positions of hundreds of known atomic transitions. Selected electrodeless discharge lamps (EDL) were used as sources for these transitions. A xenon arc continuum also aided in defining order limits and slopes. Table I11 lists the map for three widespread orders. With the map of the echelle stored in the computer, scanning is accomplishedby specifying three parameters: initial wavelength of the scan, distance to scan, and the desired quality of the spectrum. Quality in this case is defied as the number of grating steps between each spectral point taken by the computer. For high-resolution spectra, this would have a value of 1, for lowresolution spectra this might have a value of 10,20, or more. A quality of 20 would correspond approximately to 0.005 nm, depending upon the order (also see Table 111). For a scan, the stepper motor positions of the initial wavelength are calculated as offsets from the position of the starting wavelength for the order. The length of the scan is determined as the number of steps for the wavelength range. The motors are sent to this initial wavelength. The motor(s) are then incremented the appropriate amount for the requested quality, and the intensity of the spectral point is measured with the electrometer. This data point is sent to the minicomputer while the microcomputer moves the motor(s) to the next spectral point, taking into account the slope of the order. The minicomputer buffers the data to the disk while the spectrum is being taken. The procedure of moving the motors and taking intensity measurements is repeated until the desired wavelength range is covered. At this point, several forms of analysis are available for the
ANALYTICAL CHEMISTRY, VOL. 53, NO. 6, MAY 1981 * 773
Table IV. Monochromator Comparison SMI Echelle
focal length aperature grating dimensions groove density dispersion (RLD) at 200 nm 400 nm 600 nm 200 nm resolution at 400 nm 600 nm
0.75 m F613 96 mm x 46 mm high 79 grooves/mm 0.067 nm/mm 0.133 nm/mrn 0.200 nm/mm 0.0019 nm (25 pm slit) 0.0043 nm (25 pm slit) 0.0071 nm (25 hm slit)
spectrum just acquired. Our current software capabilities are described below. COMPUTER PROGRAMS Smoothing. Smoothing is usually the first treatment for the spectrum, This is an “n” point moving average, and depending upon the intensity of the spectaum, it may not be necessary. Smoothing is useful for low-intensity noisy spectra. However, the process tends to distort the true transition center and therefore is not used when trying to accurately position unknown transitions. Normalization. Normalization of intensity and/or wavelength is often desirable. The intensity normalization is useful for comparing spectra from different sources or the same source with different slit widths. With the multirange electrometer, 5 orders of magnitude of usable dynamic range can be stored digitally, thus making intensity normalization a necessary treatment prior to output of the spectra. The wavelength normalization is useful for comparing spectra taken at different qualities. It is also useful when plotting spectra from a continuous set of orders as one spectra. The normalization is necessary because the spectral unit per stepper motor step is, as mentioned above, ix function of order. Accumulation. Spect,ra can be added together to accumulate the same wavelength range from different scans. This is used to enhance the signal-to-noise ratio instead of smoothing when the center position of an unknown transition is needed with great accuracy. Several spectral scans of the same region are taken and then added together. This has the effect of smoothing the intensity values of the scan but not distorting the line center of the transitions. Transition Center Determination. Position determination of unknown transitions can be accomplished. First potential peaks are found by looking for a change in slope of the spectrum. This locates the peaks but also locates noise on the peaks as well. Then these groups of noise peaks around each transition are used to find the transition center by locating the centroid of each of the groups. By use of the centroid of the groups, unknown transitions are identified relative to known transitions in the spectrum. This part of the identification process requires the spectroscopist to identify the known peaks in the spectrum and feed this information to the computer. The centroid method represents an improvement over using the most intense peak within a group of peaks for identifying transitions. RESULTS AND DISCUSSrON Several factors were used to evaluate the performance of the system at three widespread orders of the spectrum. First was mechanical resolution in terms of nanometers per stepper motor step. This was accomplished during the mapping phase of system development by scanning orders with known transitions and determining the number of steps between these transitions (see Table 111). The second means of evaluation was to compare the manufacturers’ specifications of the echelle with that of a Spex
Spex Industries 0.75 m f/7.0 102 mm X 102 mm 1200 grooves/mm 11.0 nm/mm 11.0 nm/mm 11.0 nm/mm 0.011 nm (10 pm slit) 0.011 nm (10 pm slit) 0.011 _- nm (10 pm slit)
Industries 0.75-m monochromator (see Table IV). As can be seen, the overall resolution of the echelle is approximately an order of magnitude better while having the same focal length. Next a precision study was undertaken to determine how repeatably the motors could be positioned at a specified point. Experimentally, this point was chosen as the peak center of the A1 1308.2155-nm transition in order 73, using a hollow cathode lamp (HCL) as the source. The prism and the grating were positioned to the base line of the lower wavelength side of this transition. This point was defined as the base, or reference, position of the scan. All precision measurements were relative to this point. Both the prism and the grating motors were then moved 8192 steps away from this base position and returned to the base again. A scan of the transition, base line to base line, was acquired, and the peak center was determined by calculating the centroid of the scan. The center of the transition was the precision determining value of the experiment, that is, the number of steps between the previously defined base point and the center. How precisely this experiment could be repeated would determine the positional precision of the system. The procedure of moving away from the base point, returning, and scanning across the transition was repeated 10 times. For the 10 scans, the standard deviation of the peak centers was 0.95 steps. This converts to 0.00015 nm for this order. Sequentially, as the scans were taken, the individual peak centers varied randomly from the mean peak center of all the scans. This means that the standard deviation was due to noise in the spectra and not in loss of stepper motor position or gear lash. This study proved that the precision in positioning the motors was more than sufficient for the resolution of the spectra acquired with the echelle. To visually demonstrate the scanning capability of the echelle, we chose three orders across the spectral range of the monochromator. The figures associated with these scans were taken by a chart recorder coupled with channel seven of the electrometer (see Figure 1). Figure 3a is a scan of a Mn HCl in order 56. The sensitivity of the chart recorder was chosen to keep the 403-nm triplet on scale. The other Mn transitions in the order appear insignificant due to the extreme intensity of this triplet. However, all peaks in the spectra were digitally located by the electrometer and stored for the order by the computer. Figure 3b was obtained with an increase in sensitivity of 10 over Figure 3a to observe the lesser intense transitions. There appears to be two transitions in the 398.6-nm region, and thus, this area was chosen for a slower, shorter range scan with higher quality (see Figure 3c). The 398.6824 and 398.7098-nm Mn transitions can be seen separated as well as additional spectral features. The digital scans permitted the positions of all the transitions to be measured with a precision of better than 0.05 nm for fast, full order scans.
774
ANALYTICAL CHEMISTRY, VOL. 53, NO. 6, MAY 1981
1.5
nm
2.0 nm I
_lL
d
a.b.c
b
fi
2.0
nm I
d
b
0.1 nm
a
Figure 4. Aluminum hollow cathode lamp operated at 20 mA and scanned in order 73: Figure 4a scan speed 0.6 nm/min, Figure 4b scan speed 0.02 nmlmin; (a) AI 1308,2155nm, (b) AI 1309.2713 nm, (c) AI I 309.2842 nm.
to be an unclassified Co transition.
Figure 3. Manganese hollow cathode lamp operated at 8 mA and scanned in order 56: Figure 3a,b scan speed 0.8 nmlmin, Figure 3c scan speed 0.08 nmlmin; (a) Mn 1398.5241 nm, (b) Mn 1398.6826 nm, (c) Mn 1398.7098 nm, (d) Mn 1401,8102 nm, (e) Mn 1403.0755 nm, (f) Mn 1403.3073 nm, (9) Mn 1403.4490 nm, (h) MnI 404.1361
nm. Next, an A1 HCL was scanned in order 73 (see Figure 4a). Then the monochromator was scanned slowly around the 309.2-nm doublet (see Figure 4b). Base line separation was nearly achieved for the A1 I 309.2842-nm transition and the significantly more intense 309.2713-nm A1 I transition. Finally, a Go HCL was scanned in order 88. This order contains a large number of Co transitions (see Figure 5a). To demonstrate the resolving power for this region, the Co doublet at 255.3 nm was scanned as seen in Figure 5b. The doublet was resolved, but of more interest was the shoulder on the high wavelength side of the 255.3374-nm transition. The possibility of an order interference was experimentally ruled out. Other neon-filled HCLs were scanned to check for the possibility of a Ne transition, and none were found. It appears
CONCLUSION The scanning echelle system was designed and built with nondestructive modification of the SMImonochromator. The design centered on ease of both hardware interfacing and software implementation. No compromises had to be made between real-time spectra acquisition and analysis routines because of the dual computer arrangement. Thus, the physical layout and building, though not trivial by any means, was fairly simple and straightforward. As was previously mentioned, by digitally storing spectra, transitions could be positioned within f0.05 nm for a full order scan (in order sa), providing that a t least three reference transitions were assigned throughout the range of the order. Of course, the 0.05 nm value is order dependent. The application of the system in this manner will be extremely useful for the systematic indexing of transitions from sources like the ICP. This can be beneficial to those who are doing routine analysis as well as those who are doing more fundamental research. This system should prove valuable in studies requiring precise measurements such as spectral overlap problems. In the best case, the instrument showed the capability of base
ANALYTICAL CHEMISTRY, VOL.
I
I
53,NO. 6,
M A Y 1981
775
combination of theoretical and experimental data can be brought together to better understand the effects of such overlaps. Many years of work have been put into the system to make it a viable instrument for use in the field of atomic spectroscopy. It is hoped that by a continued effort, a better understanding of the special properties of the echelle monochromator and fundamental atomic spectrocopy can be obtained. LITERATURE CITED
0.05
nm
Larson, G. F.; Fassel, V. A.; Wlnge, R. D.; Knlseley, R. N. Appl. Spectrosc. 1976, 30, 384. Boumans, P. W. J. M. Spectrochim. Acta, Part B 1976, 318, 145. Marclello, L.; Ward, A. F. Jarrel-Ash Plasma Newsletter 1976, 1 , 12. Skogerboe, R. K.; Lamothe, P. J.; Bastlaans, G. J.; Freeland, S. J.; Coleman, 0.N. App. Spectrosc. 1976, 30, 495. Koirtyohann, S. R.; Glass, E. D.; Yates, D. A.; Hlnderberger, E. J.; Llchte, F. E. Anal. Chem. 1977, 49, 1121. Fassel, V. A. Science 1978, 202, 13. Larson, G. F.; Fassel, V. A. Appl. Spectrosc. 1979, 33, 592. Winge, R. K.; Peterson, V. J.; Fassel, V. A. Appl. Spectrosc. 1979,
. --w, -mi - -.
Johnson, 0.W.; Taylor, H. E.; Skogerboe, R. K. Appl. Spectrosc. 1079. .- . -, 33. - - , 451. .- . . Skogerboe, R. K.; Urasa, I. T.; Coleman, G. N. Appl, Spectrosc. 1076. 30. 500. Skogerboe, R. K.; Coleman, G. N. Appl. Spectrosc. 1976, 30, 504. Klueppel, R. J.; Coleman, D. M.; Eaton, W. S.; Goldstein, S. A.; Sacks, S. A.; Walters, J. P. Spectrochim. Acta, Part B 1978, 338, 1. Lovett, R. J.; Parsons, M. L. Spectrochim. Acta Part B 1960, 358,
615.
Flgure 5. Cobalt hollow cathode lamp operated at 15 m A and scanned in order 88: Figure 5a scan speed 0.3 nm/min, Flgure 5b scan speed 0.023 nm/min; (a) Co I 254.4253 nm, (b) Co I 254.930 nm, (c) C o I 255.3003 nm, (d) Co I 255.3374 nm, (e) C o I 256.2146 nm, (f) C o I 256.7346 nm, (9) Co I 257.4350 nm.
line resolution for transitions 0.01 nm apart. This can be done while preserving a positional precision of approximately O.OOO1 nm, again depending upon the order scannled. From previous work done in this laboratory (13,14,22),theoretical models of the spectral overlap problem have been developed. Now, with the availability of this high resolution, coupled with the power of computer control and analysis of such spectra, the
Forster, A. R.; Anderson, D. L.; Lovett, R. J.; Parsons, M. L., submitted for publication in Spectrochim. Acta. Keliher, P. N.; Wohlers, C. C. Anal. Chem. 1976, 48, 333A. Zander, A. T.; Keliher, P. N. Appl. Spectrosc. 1979, 33, 499. Parsons, M. L.; Forster, A. R.; Anderson, D. L. Fourth Annual Meeting of FACSS, Abstract 37, Nov 1977. Parsons, M. L.; Forster, A. R.; Anderson, D. L. “Abstracts of Papers”, 175th National Meeting of the American Chemlcal Society, Anaheim, CA, March 1978; Amerlcan Chemical Society: Washington, DC, Abstract ANAL 73. Forster, A. R.; Anderson, D. L.; Parsons, M. L. Second Chemical Congress of the North Amerlcan Continent, Abstract Anal 217, Aug 1980. Tllden, S. B.; Denton, M. B. J. Autom. Chem. 1979, 1 , 128. Moore, C. H. Astron. Astrophys. Suppl. 1974, 15. 497. Parsons, M. L; Forster, A. R.; Anderson, D. L. “An Atlas of Spectral Interferences in ICP Spectroscopy”, 1st ed.; Plenum: New York, 1980.
RECEIVED for review November 14,1980. Accepted January 26, 1981. The authors wish to thank SMI for their partial support in providing the echelle monochromator and Arizona State University and Chevron Research Co. for their continued support of our research.
