406
Anal. Chem. 1985, 57. 406-411
the square wave frequency does not change appreciably. This condition is well met in the work reported here, but it would not be correct a t all with very fast scans. Preliminary experimental and theoretical work indicates that in very fast scans individual interferogram components lose intensity and are shifted in phase by amounts determined by transit time and scan rate, but that the FT method is still valid. However, further theoretical and experimental investigations are needed before very rapid scanning can be employed. Other Applications. Although this work centers on FT IMS, the same general approach is applicable to any time dispersive technique. A time dispersive technique separates the components of a mixture on the basis of propagation times of the individual components through some medium. In addition to IMS, time dispersive techniques include chromatography, electrophoresis, time of flight mass spectrometry, TOF spectrophotometry, RADAR, and LIDAR. T O F mass spectrometry in particular could benefit from the FT method. In any appication the essential elements of the FT method are (1)modulation of the source (or injector or transmitter) by a continuous frequency rather than a narrow pulse, (2) multiplication of the detected signal by the source modulation function and long time constant averaging of the product function, (3) obtaining a signal S(v) by sweeping the modulation frequency, and (4) recovering the time dispersed signal as normally measured by calculating the magnitude of the FT of S(v). In a particular application the potential benefits of the FT method would arise from one or more of the following:
(1) increased duty cycle of the sample source, which could be used to increase signal levels, increase sensitivity, or speed data collection, (2) reduction of measurement broadening without loss of sensitivity, (3) multiplexing, since signals from all components of a sample are detected simultaneously, or (4) reduction of need for fast detection and recording electronics, since the recording electronics need be a t most only as fast as the sweep of the modulation signal. ACKNOWLEDGMENT We wish to express our appreciation to Steven D. Brown and John M. Frame for helpful discussions.
LITERATURE CITED Cohen. M. J.; Karasek, F. W. J . Chromatogr. Sci. 1970, 8 , 330. Hill, H. H.. Jr.; Baim, M. A. I n "Plasma Chromatography"; Carr, T. W., Ed.; Plenum: New York, 1984; p 143. Karasek, F. W.; Keller. R. A. J . Chromatogr. Sci. 1972, 10, 626. Karasek, F. W.; Hill. H. H., Jr.; Kim, S. H.; Rokushika, S. J. J . Chromatogr. 1977, 135. 329. Baim, M. A.; Hill, H. H., Jr. Anal. Chem. 1982, 5 4 , 38. Baim, M. A,; Eatherton, R. L.; Hill, H. H., Jr. Anal. Chem. 1983, 55, 1761. Bracewell, R. N. "The Fourier Transform and Its Applications", 2nd ed.; McGraw-Hill: New York, 1978; Chapters 3 and 4.
RECEIVED for review July 23,1984. Accepted October 19,1984. This work was supported in part by a grant from the Public Health Service. The work was presented in part at the Northwest Regional Meeting, American Chemical Society, June 8. 1984.
Tree Ring Wood Analysis after Hydrogen Peroxide Pressure Decomposition with Inductively Coupled Plasma Atomic Emission Spectrometry and Electrothermal Vaporization Henryk Matusiewicz' and Ramon M. Barnes*
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003-0035
A method utlllzlng pressure decompodtlonto mlnhnlze sample pretreatment Is described for the lnductlvely coupled plasma atomic emlsslon spectrometric analysis of red spruce and sugar maple. Cores collected from trees growlng on Camels Hump Mountain, Vermont, were dlvided Into decade lncrements In order to monltor the temporal changes In concentrations of 21 elements. Dried wood samples were decomposed In a bomb made of Teflon wiih 50% hydrogen peroxlde heated In an oven at 125 OC for 4 h. The dlgestlon permitted use of aqueous standards and mlnlmlzed any potentlal matrlx effects. The element concentrations were obtained sequentlally by electrothermal vaporlratlon ICP-AES uslng 5 pL sample allquots. The method preclslon varied between 3 and 12%. Elements formlng oxyanlons (AI, As, Fe, Ge, Mn, SI, V) were found at elevated concentratlons durlng the most recent three decades, whlle other metal (e.g., Mg, Zn) concentrations were unchanged or decreased.
Many studies have been carried out to investigate the uptake of various elements by plants, especially in forest ecoOn leave from Technical University of Poznafi, Department of Analytical Chemistry, 60-965 Poznaii, Poland. 0003-2700/85/0357-0406$01 S O / O
systems (1). Tree rings, which represent a chronological record of elemental changes that are not contaminated naturally by outside sources like lake-core sediments or glacial cores, can be considered indicators that record environmental disturbances. The occurrence of elevated trace and especially toxic metals concentrations in accurately dated tree-ring sequences from trees in certain regions is closely linked to environmental effects (e.g., acid rain), and these rings represent records of environmental influence during the past several years ( 2 ) . Thus, analysis of tree rings for metals is an important indicator of atmospheric pollution. Some effort has been devoted recently to detecting the presence of heavy metals in wood (3-16). A new method of sample preparation for cellulose materials was sought in this research that would be applicable to wood and yield a solution from which elements could be determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Bomb digestion with hydrogen peroxide was evaluated because it provides a relatively rapid means of decomposition that assures complete recovery of elements in tree ring wood. Analysis for trace and major elements in solid samples generally requires decomposition of the organic matter followed by dissolution leading to a solution for subsequent analytical determination. This ashing may be achieved by 0 1985 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 57, NO. 2, FEBRUARY 1985
specially constructed high-pressure the steel vessel was applied for pressure decomposition a t 370 "C of more than 30 different materials (25). T h e analytical disadvantage of these two methods is the contamination hazard of metals from the ferrous sulfate or steel vessel. Electrothermal vaporization (ETV) devices have proven to be useful for introduction of a microvolume (e.g., 5 WL)of analyte into the ICP for multielement analysis, and several applications have recently been reported. For example, in our laboratory Barnes and Fodor (26) utilized a modified graphite rod with a Varian CRA-90 vaporizer, and Matusiewicz and Barnes (27) improved this E T V system for analyte introduction into an ICP. Recently a n IL655 controlled temperature furnace was adapted for ICP-AES (28, 29). T h e object of this work was t o develop a suitable method for decomposing and analyzing small quantities (about 1C-120 mg) of tree ring woods for 21 elements. The method described utilizes a pressurized wood digestion with hydrogen peroxide followed by metal analysis by means of ETV/ICP-AES.
Table I Electrothermal Vaporization-ICP Compromise Operating Conditions parameter
compromise condition
power, kW reflected power, W outer argon flow rate, L/min sample volume, FL ETV chamber flow rates, L/min inner outer vaporizer setting drying ashing vaporization heating rate
407
0.5
Flgure 1. Maximum weight of wood decomposed in hydrogen peroxide: of 50% H,O,. Densities correspond to the following woods: 0.13 balsa (Ochroma Lagopus), 0.35 eastern whRe pine (Pinus sfrobusL .), 0.40 eastern spruce (Picea gbuca Voss .), 0.50 black cherry (Prunus serotina Ehrh.), 0.63 hard maple (Acer saccharum Marsh .), 0.64 beech (Fagus grandifoh Ehrh .), 0.75 true hickory (Carya ovata Mill. K . Koch.), 0.90 purple heart (feltogyne spp .), and 1.10 schwartz (Bannia ). ( X ) 5 mL of 30% H,02, (0)5 mL
multielement analysis although the present determinations were performed sequentially with a manual monochromator. Those parameters that critically affected the observed signal-to-background ratio (SBR) used for optimization were the carrier (inner and outer) argon gas flow rates of the double-wall chamber, plasma power, and the temperature program selection of the electrothermal vaporizer. In conventional electrothermal vaporizer systems caution is necessary in the drying stage if sample loss through rapid boiling is to be avoided. Sample solutions were dried gently a t 110 "C for 60 s to avoid sample sputtering and to remove the solvent completely. After the wood digestion procedure with hydrogen peroxide, the resulting solution is water, and for aqueous samples the ashing step should not be necessary with ETV. When an ashing setting was used, a more reproducible vaporization step was obtained and precision was slightly better. However, in the technique finally adopted, the conventional ashing stage of the electrothermal system is omitted to reduce total analysis time and simplify the temperature program procedure. Selection of analytical lines, listed in Table 11, was based on the prominent lines summarized by Boumans (35),Winge et al. (36),Anderson et al. (37), and Boumans (38). The wavelengths given were chosen to provide a reasonable compromise between optimum analyte sensitivity and minimum spectral interferences, if any, from the major elements (Ca, K, Mg) present in the tree ring wood sample solutions analyzed. By use of the constant plasma conditions and compromise conditions for graphite rod electrothermal vaporization for each element, the limits of detection obtained for 5-WLaliquots are shown in Table 11. The values are presented in terms of both analyte mass (qL) and concentration (cL) to simplify comparison. The lowest quantitatively determinable concentrations (LQD), calculated as 15sb, obtained under routine conditions for elements in tree ring wood are also given in Table 11. Simultaneous or off-peak background measurements for each element were not applied because of the very sample volume available, therefore, the background values measured a t the analytical wavelength for the blank solutions were employed as background correction with all samples. The measurement precision, expressed as relative standard
element A1 As Ba Ca Cd cu Fe K Mg Mn Na Pb Si Sr
v
Zn
found, wg/g
s,,~
50 0.25 10 235
4.7 9.4 4.5 3.2
90
f
I
0.60
18 30 50 0.17 63 0.24 39 0.91 0.11 5.1
5.3 3.9 8.1 3.0 2.9 6.2 6.9 4.2 5.5 5.0 7.1
conditional IAEA values, wg/g reported confidence limits' 44d
13-53
e
9 24 1 0.002 0.59 11
6-12 227-256 0.001-0.006 0.47-0.94 7-15
e
53 0.15 56 0.25
46-67 0.12-0.21 49-64 0.22-0.33
e
0.65 0.09
0.54-0.96 0.07-0.10
e
Single analysis throughout; results given as wg/g of dry weight of sample; triplicate determinations. Relative standard deviation of triplicate measurements from a single sample preparation. Confidence limits calculated at a significance of 0.05. Not certified, values for information purposes. e Not reported. 'Below limit of detection. B, Be, Ge, Li, and Se are also below the limit of detection. deviation (sJ, was 3-12% (Table 11). Data for s, calculations were obtained from calibration curves recorded on different days and with different graphite rods. The tree-ring wood analysis results obtained by calibrating with synthetic aqueous standard solutions and single-element standard additions to wood after decomposition in hydrogen peroxide are essentially identical. Therefore, for routine measurements of tree samples, the analysis data are based on calibration using multielement synthetic standard solutions. Analysis of IAEA Cotton Cellulose. Since no wood or similar botanical standard reference materials were available initially, the accuracy of the method was tested for tree ring wood by analyzing an IAEA Cotton Cellulose Reference (V-9), which is presently the only material of similar composition prepared. Cellulose is the major wood component, and the inorganic constituents amount to less than 0.5% in most woods of the temperate zone (39). Some typical carbon, hydrogen, and oxygen values for woods are compared with the approximate composition of the IAEA Cotton Cellulose in Table 111. Although the IAEA reference is not yet certified (40), this material was used to verify the overall performance of the analytical technique and decomposition procedure. The sample was analyzed before knowing the preliminary certification values, and results are presented in Table IV. In virtually all cases (except Fe), our results are well within the IAEA confidence limits. This suggests the validity of the present decomposition procedure and operating conditions. The s, values for triplicate determinations from a single V-9 sample preparation are generally lower than the s, data in
410
ANALYTICAL CHEMISTRY, VOL. 57, NO. 2, FEBRUARY 1985
Table V. Element Concentration in p g / g of Dry Tree-Core Wood for Red Spruce Sample wt,
yeara
1791-1800 1801-1810 1811-1820 1821-1830 1831-1840 1841-1850 1851-1860 1861-1870 1871-1880 1881-1890 1891-1900 1901-1910 1911-1920 1921-1930 1931-1940 1941-1950 1951-1960 1961-1970 1971-1980 bark
mg
13 19 26 36 36 45 25 53 44 67 98 88 91 121
32 47 60 69 24 44
A1
As
Ba
Ca
Cu
Fe
K
Mg
Mn
Na
Si
Sr
V
Zn
9.3 8.9 7.8 6.5 6.1 8.2 7.5 9.2 8.9 11.2 12.3 9.2 7.8 9.9 10.2 11.3 15.0 18.8 23.8 67.0
ND ND ND ND ND ND ND ND ND ND 2.5 2.8 2.0 3.0 3.8 4.2 4.9 6.2 8.3 16.1
31 41 38 30 35 37 39 29 27 34 35 36 37 40 39 31 42 43 39 180
730 762 810 900 875 860 815 820 836 860 885 825 730 762 810 880 900 988 936 8745
1.4 1.2
119 120 102 98 91 85 80 73 70 66 68 70 73 98 144 149 153 157 280 395
500 510 540 495 487 470 455 438 410
635 639 583 571 528 571 500 524 495 480 468 439 442 412 382 351 310 287 166 787
435 420 410 405 394 405 400 406 392 400 394 402 398 400 406 410 423 430 635 590
134 105 35 35 30 37 38 30
6.2 5.3 4.1 3.7 2.3 1.7 1.8 2.1
17
21 24
1.7
ND ND ND ND ND ND ND ND ND ND ND 0.1 0.3 0.7
3.2 7.5 9.1 16.8
36 38 30 28 34 35 31 34 30 29 26 31 32 36 37 40 28 15 3
11.2
42
1.9 2.0 2.1 1.7 1.6 1.1 2.1 2.2
2.4 2.3 2.0 1.9 2.0 1.8
1.6 1.2 1.0
11.0
412
390 401 508 522 538 540 638 758 873 1510
1.6 2.0 2.4 2.8 3.5 5.8 8.9 10.1 12.3 12.5 24.0
30 30 28 29 38 36 33 35 37 39
18 20 22
15 19 21
14 13 18 19 25 26 20 20 21 22
19 23 50
1.1
"Decade range indicated as established from tree-ring counting. Be, Cd, and Pb were not detected in wood. Concentrations in bark were 0.3 pug of Be/g, 5.4 pug of Cd/g, and 2 1 pg of Pg/g. B, Ge, Li, and Se were below the limit of detection. Table VI. Element Concentrations in p g / g of Dry Tree-Core Wood for Sugar Maple Sample
yeara 1879-1880 1881-1890 1891-1900 1901-1910 1911-1920 1921-1930 1931-1940 1941-1950 1951-1960 1961-1970 1971-1980 1981-1982 bark
wt,
mg
A1
As
Ba
Ca
Cu
Fe
Ge
K
Mg
58 233 297 199 292 439 386 216 229 118
12.0 11.0
ND ND ND ND ND 1.5 1.7 1.6 2.9 3.5 5.2 8.3 28.0
52 55 56 47 49 58 60 62 53 62 63 65 402
2750 2510 2305 2418 2525 2812 3083 3002 3025 2919 2929 2820 14560
0.7 0.8 0.6 0.8 0.7 0.7 0.7 0.9 1.3 1.0 1.8 1.7 26.0
25 29 23 27
ND ND ND ND ND ND ND ND 2.5 3.8 8.5 23.5 109
1541 1500 1421 1487 1522 1502 1512 1499 1390 1310 1275 1246 1200
1026 1053 1200 1075 1101 1029 1084 921 824 790 669 618 1651
41 17
107
11.1
10.0 9.3 8.5 10.7 16.1 20.1 28.3 25.9 26.1 93.1
22
24 21
26 27 38 49 108 72
Mn 2.0 2.1
4.0 4.0 5.8 6.3 7.7 21.8 25.8 27.2
29.1 61.1 143
Na
Si
Sr
V
Zn
307 238 128 110 93 88 83 62 52 37 42 40 116
16 17 13 10 15 18
31 32 38 30 29 27 34 36 38 39 36 35 210
ND ND ND ND
24
21
23 24 20 27 22 11
ND 0.1
0.8 3.1 15.2 30.0 33.0 39.1 33.6
27
24 28 26 25 27 28 24
25 17
16 45
"Decade range indicated as established from tree-ring counting except for single year sample 1791-1800. ND indicates not detected. Be, Cd, and Pb were not detected in wood, and 0.5 pg of Be/g, 7.0 pg of Cd/g, and 32 Wg of Pb/g were measured in bark. B, Li, and Se were below the limit of detection. Table I1 owing to the improved ETV system (28,29)employed for the cotton cellulose analysis. Tree Ring Sample Analysis. T o assess the pract,ical utility of the electrothermal vaporization-ICP combination, the determination of 21 elements in tree-ring wood samples was undertaken. The mean concentration values of 14 or 15 elements (in pg/g dry matter) in two tree ring samples for each growth decade together with associated bark samples are summarized in Table V and VI. All concentrations were determined from calibration curves prepared from multielement aqueous synthetic standards. In all the wood and bark samples analyzed, the concentrations of B, Ge, Li, and Se were below the ETV-ICP limits of detection. Except for bark samples, the concentrations of Be, Cd, and P b also were below detection. The concentrations of almost all elements found in bark are higher than those in both tree cores. The major exceptions are for Fe, K, Si, and V in spruce and Fe and V in maple. This trend is contrary to that expected if the slightly viscous bark solutions resulted in a concentration bias. The elevated concentrations may be related to different bark exposure times or surface condition or might be indicative of anthropogenic sources. A number of trends in both sets of woods samples are apparent. In the core wood polyvalent elements forming
oxyanions (i.e., Al, As, Fe, Ge, Mn, Si, and V) exhibit welldefined increases in concentrations during recent decades. Although individual differences exist, these concentration increases occur beginning with the 1941-1950 samples, and pronounced increases are observed during the last decade. Since tree rings correspond to years of tree life, tree-core sample metal content can be correlated to past environmental conditions, pollution, or contamination (2, 41-44). Similar results for Mn (8), Ge ( 1 3 ) ,and A1 ( 2 , 41, 44) were reported previously. On the other hand, the concentrations of Mg and Zn in both samples decrease. While Cu concentrations decrease in the spruce, they increase in the maple, and K concentrations increase in the spruce and decrease in the maple. Sodium concentrations drop during the early decades in both cores to reach a common concentration in contemporay decades. Alkaline-earth elements exhibit no strong concentration trends in either core sample. These results suggest that some maintanence of charge balance may occur, wherein enhanced concentrations of polyvalent cations (Al, As, Fe, Mn, etc.) may offset the lower concentrations of Mg and Zn ions. Finally, alkalines (K, Na), alkaline earths (Ba, Ca, Mg, Sr), and Si and V exist a t higher concentrations in the maple sample than in the spruce; whereas, Cu, Fe, Mn, and Zn concentrations in the spruce are higher than in the maple.
ANALYTICAL CHEMISTRY, VOL. 57, NO. 2, FEBRUARY 1985
This investigation was not intended to characterize the elemental content of the species on the basis of two specimens from two trees, but the similarity of chronological concentration variations in the two species, except for Cu and K, is striking and suggests that application of the analytical procedure developed to additional samples would be useful.
CONCLUSIONS The use of pressure-decomposition vessels for the wet oxidation of wood with 50% hydrogen peroxide (orland 30% HzOz) is recommended. Hydrogen peroxide (50% m/v) provides a convenient and very effective means of destroying cellulose materials. This single wet decomposition procedure completely decomposes and dissolves the samples without leaving any residues. Reduced labor and time are achieved compared to conventional methods, and only small amounts of HZOzare needed. Reduced chemical costs, low contamination, very low blanks, small interferences, and a concentrated sample solution (about 1:2) make the measurement of a number of elements possible in only about 50 mg of a tree ring wood sample. This technique could be applied also in the simultaneous multielement mode to microamounts of samples and should find application in the analysis of other cellulose sample types or, for example, paper and paper products (e.g., paperboard) or cotton swabs in forensic investigation. The results presented indicated that many environmentally related elements present in tree ring samples can be detected and analyzed by the described ETV/ICP technique. The dried tree ring samples require only very simple dissolution and analysis. These dendro-analysis experiments suggest that tree-ring wood from long-lived species may be used to monitor variation of metal ion concentrations to establish a basis for long-term environmental pollution histories. However, regression analysis must be performed to determine if a correlation actually exists between metal concentration in the trees and the environmental metal concentrations. Finding triple the concentrations of some metals absorbed by the bark, which is consistent with Barnes et al. (8) and Nurmesniemi and Hayrynen (45),supports the idea that bark might be used as a collector of atmospheric metals. Growing indications exist to demonstrate widespread dieback and decline of forest are caused by short- and long-range transport of air pollutants and acid deposition. The present multielement investigation indicates that polyvalent cations that tend to form oxyanions increase in concentration in recent tree rings while other cation concentrations remain unchanged or decrease. The possibility that the trees are starved of some nutrients (e.g., Mg, Zn) as well as are poisoned by phytotoxic metals should be examined. Further verification of these described trends with additional samples and determination of other elements including Cr, Ti, and Mo may provide the basis for understanding the change in the metal uptake by selected types of trees with time.
ACKNOWLEDGMENT The authors are grateful to the Department of Botany, University of Vermont, Burlington, for providing the samples of the tree rings used in this study.
411
Registry No. Al, 7429-90-5;As, 7440-38-2; Ba, 7440-39-3; Ca, 7440-70-2; Cu, 7440-50-8; Fe, 7439-89-6; K, 7440-09-7; Mg, 7439-95-4; Mn, 7439-96-5; Na, 7440-23-5; Si, 7440-21-3; Sr, 7440-24-6; V, 7440-62-2; Zn, 7440-66-6; hydrogen peroxide, 7722-84-1.
LITERATURE CITED (1) Ulrich, B., Pankrath, J., Ed. "Effects of Accumulation of Air Pollutants in Forest Ecosystems", D. Reidel Publishing Company: Dordrecht, 1983. (2) Baes, C. F., 111; McLaughlin, S . B. Science 1984, 224, 494. (3) Meyer. J. A.; Langwig, J. E. Wood Sci. 1973, 5 , 270. (4) Ward, N. I.; Brooks, R. R.; Reeves, R. D. Environ. Poliut. 1974, 6 , 149. (5) Osterhaus, C. A.; Langwig, J. E.; Meyer, J. A. Wood Sci. 1975, 8 , 370. (6) Ricci, E. Anal. Chim. Acta 1975, 7 9 , 109. (7) Sheppard, J. C.; Funk, W. H. Environ. Sci. Technoi. 1975, 9 , 638. (8) Barnes, D.; Hamadah, M. A,; Ottaway, J. M. Sci. TotaiEnviron. 1976, 5,63. (9) Tout. R. E.; Gilboy, W. B.; Spyrou, N. M. J . Radioanal. Chem. 1977, 37, 705. 10) Hincman. P. S.;Giuffre, G.; Litman, R. Radiochem. Radioanal. Left. 1978, 33, 361. 11) Gilboy. W. B.; Mason, P. I.; Tout, R. E. J . Radioanal. Chem. 1979, 48, 327. 12) Kouris, K.; Tout, R. E.; Gilboy, W. B.; Spyrou, N. M. Archaeometry 1981, 2 3 , 95. 13) D'Auria, J. M.; Wooiey, E. F. Analyst (London) 1982, 107, 1247. 14) Bumbilovd, A.; Havrdnek, E.; Harangoz6, M. Radiochem. Radioanal. Lett. 1982, 54, 367. (15) Tanaka, J.; Ichikuni, M. Atm. Environ. 1982, 16. 2015. (16) Verbeek, A. A. Spectrochim. Acta, P a r t 8 1984, 398, 599. (17) Sansoni, B.; Panday, V. K. "Analytical Techniques for Heavy Metals in Biological Fluids"; Facchetti, S . , Ed.; Elsevier: Amsterdam, 1982; p 91. (18) Matusiewicz. H. Chem. Anal. (Warsaw) 1963, 28, 439. (19) Jackwerth, E.; Gomiscek, S. Pure Appi. Chem. 1984, 56, 479. (20) Mitchell, J. W. Talanta 1982, 2 9 . 993. (21) Moody, J. R.; Beary, E. S . Talanta 1982, 29, 1003. (22) Analytical Methods Committee Ana/yst (London) 1967, 92, 403. (23) Analytical Methods Committee Analyst (London) 1978, 101, 62. (24) Sansoni. 8.; Kracke, W. fresenius Z . Anal. Chem. 1968, 243, 209. (25) Denbsky. G. Fresenius Z . Anal. Chem. 1973, 267. 350. (26) Barnes, R. M.; Fodor, P. Specfrochim. Acta, Part 8 1983, 386, 1191. (27) Matusiewicz, H.; Barnes, R. M. Specfrochim. Acta. Part 8 1984, 398, 691. (28) Matusiewicz, H.; Barnes, R. M. Appl. Spectrosc. 1984, 38, 745. (29) Matuslewlcz, H.; Barnes, R. M. Spectrochim. Acta, Part 8 , in press. (30) Long, G. L.; Wlnefordner. J. D. Anal. Chem, 1983, 5 5 , 712A. (31) Lechler, P. J.: Leininger. R. K. Jarreli Ash Plasma News/. 1979, 2 , 8. (32) Kosta, L. Talanta 1982, 29. 985. (33) Bernas, B. Anal. Chem. 1968, 40, 1682. (34) Langmyhr, F. J.; Paus, P. E. Anal. Chim. Acta 1968, 43, 397. (35) Boumans, P. W. J. M. "Line Coincidence Tables for Inductively Coupled Plasma Atomic Emission Spectrometry"; Pergamon Press: Oxford, 1980. (36) Winge, R. K.; Peterson, V. J.; Fassel, V. A. Appi. Spectrosc. 1979, 33. 206. (37) Anderson, T. A.; Forster, A. R.; Parsons, M. L. Appl. Spectrosc. 1982. 36. 504. (38) Boumans, P. W. J. M. Spectrochim. Acta, Part 8 1983, 388, 747. (39) Browning. B. L. "The Chemistry of Wood", Wiley: New York, 1963; p 73. (40) Pszonicki, L.; Hanna, A. N.; Suschny, 0. "Report on Intercomparison V-9 of the Determinatlon of Trace Elements in Cotton Cellulose". IAEA (IAEA lRLI97) March 1983. (41) Vogeimann, H. W. Nat. History 1982, 91,8. (42) Johnson, A. H.; Siccama, T. G. Environ. Sci. Techno/. 1983, 17, 294A. (43) Tomlinson G. H.. 11 Environ. Sci. Technoi. 1983, 17, 246A. (44) Krug. E. C.; Frink, C. R. Science 1963, 221, 520. (45) Nurmesniemi, H.; Hayrynen, H. Paperi Puu-Papper M 1983, 1 1 , 700.
RECEIVED for review August 30, 1984. Accepted November 1,1984. Research supported in part by Department of Energy Contract DE-AC01-77EV-0432, and the ICP Information Newsletter. Some material in this paper was presented in part by H. Matusiewicz a t the VIth Polish Spectroanalytical Conference, May 1981, Biaiowieza, Poland.
