Anal. Chem. 1982, 5 4 , 2179-2186
below practical detection limits; for Cr, Ian, and Ni they are close.
CONCLUSION Impactor-collected aerosols were ICP-OES analyzed after digestion by HF/HN03. This treatment dissolves the samples without leaving any residues. However, the presence of large amounts of flux results in higher detection limits for the ICP-OES analysis. By the method described, the undiluted sample solution is analyzed without any volume correction which makes the measurement of a number of elements in only 0.1-1 mg of aerosol sample possible. Excluded from the list of detwminel:i elements are Si and Ni, as blank values for Si showed large variations in spite of com,plexingthe HF with H3B03, and Ni contents in the samples were too low for quantitative determination by this metlhod. The e1e:ments Ca, Mg, Al, Fe, Pb, Zn, V, Cu, and Sr can be determined simultaneously in urban aerosol samples of 1mg. In grain-size separated samples, the conccntrations necessary for determination are not reached for some elements in certain size ranges. The successful determination of those elements in all grain size fractions would require longer sample collection times.
LITERATURE CITED (1) Puxbaum, H. Fresenius' Z . Anal. Chem. 1979, 298, 110-122. (2) Lioy, ,J. P.; Watson, J. G., Jr.; Spengler, J. D. JAPCA 1980, 3 0 , 1126- 1130. (3) Pungor, E.; Polos, L. I n "Analysls of Airborne Particles by Physical Methods"; Malissa, H., Ed.; CRC Press: West Palm Beach, FL, 1978; pp 39-56. (4) Kotz, I..; Kaiser, G.; Tschopel, P.; Tolg, G. Fresenius' Z . Anal. Chem. 1972, 260, 207-209. ( 5 ) Prelning, 0.; Berner, A. EPA-600/2-79-105; iInvironmental Protection Agency: Research Triangle Park, NC, 1979. (6) Puxbaum, H.; IRendl, J. Mikrochim. Acta, in ~press.
2179
(7) Puxbaum, H.; Wopenka, B., unpublished work, Vienna, Austria, 1961. (8) Dorn, G. Paper presented at the International Winter Conference 1980. Developments in Atomlc Plasma Spectrochemical Analysis, San Juan, PR, 1980. (9) Aziz, A.; Broekaert, J. A. C.; Leis, F. Spectrochim. Acta, Part8 1981, 3 6 6 , 251-260. (10) Broekaert, J. A. C., Dortmund, Federal Republic of Germany, 1982, unpublished work. (11) Greenfield, S.; Jones, I.; Berry, C. T. Analyst (London) 1964, 8 9 , 7 13-720. (12) Scott, R. H.; Fassel, V. A.; Kniseley, R. N.; Nixon, D. E. Anal. Chem. 1975, 4 6 , 75-80. (13) Broekaert, J. A. C.; Leis, F.; Laqua, K. Spectrochim. Acta. Part 8 1979, 3 4 8 , 73-84. (14) Broekaert, J. A. C.; Leis, F.; Laqua, K. Paper presented at the International Winter Conference 1980; Developments In Atomic Plasma Spectrochemlcal Analysls, San Juan, PR, 1980. (15) Kaiser, H.; Specker. H. Z . Anal. Chem. 1958, 149, 46-66. (16) Aziz, A.; Broekaert, J. A. C.; Leis, F. Spectrochlm.Acta, Part8 1982, 3 7 6 , 369-379. (17) Winge, R. K.; Peterson, V. J.; Fassei, V. A. Appl. Spectrosc. 1979, 3 3 , 206-219. (18) Laqua, K. I n "Uimanns Encyklopadie der technischen Chemie" Part 5, Verlag Chemie: Weinhelm, 1980. (19) Frauerwieser, G. Thesis, Technical University of Vienna, Vienna, Austria, 1980. (20) Mallssa, H. I n "Analytlcal Chemistry and Air Pollutants" (Ger.); Malissa, H., Puxbaum, H., Ed.; Institute for Analytical Chemistry, Technical University of Vienna: Vienna, Austria, 1981; pp 1-7. (21) Broekaert, J. A. C.; Leis, F.; Laqua, K. Spectrochlm. Acta, Part B 1979, 3 4 8 , 167-175. (22) Broekaert, J. A. C.; Leis, F. Anal. Chlm. Acta 1979, 109. 73-83. (23) Pearce, R. W. B.; Gaydon, A. G. "The Identificatlon of Molecular Spectra"; Chapman and Hall: London, 1950. (24) Nalimov, V. V. "The Application of Mathematical Statistics to Chemical Analysis"; Pergamon Press: Oxford, 1963. (25) Mallssa, H.; Puxbaum, H.; Wopenka, 8. Paper presented at the Second European Symposium on Physico-Chemlcal Behaviour of Atmospheric Pollutants, Varese, Italy, 1981. (26) Wopenka, €3.; Puxbaum, H.; Broekaert, J. A. C., Unpublished work, Vienna, Austria, 1981. (27) McQuaker, N. R.; Kluckner, P. D.; Chang, G. N. Anal. Chem. 1979, 5 1 , 888-895.
RECEIVED for review March 2,1982. Accepted August 2,1982.
Direct Determination of Metallic Elements in Solid, Powder Samples with Electrically Vaporized Thin Film Atomic Emission Spectrornetry J. Goldberg' anid R. Sacks" Department of Chelmistty, University of Michigan, Ann Arbor, Michigan 48 109
The hlghly lumlrious Ag vapor plasmas; produced by the electrlcal vaporlzatlon of Ag thin films with 9SO-J, 8-kV, 1200-pH discharges are used as atomization cells and excitation sources folr the direct determlnatlon of V, Mn, Cr, Ni, Sr, Cd, Zn, and Pb In solld powder samples. High clrcult Inductance reduces particle size effects and 1.0-mg samples with partlcles in ithe 20-30 pm size range can be analyzed wlth aqueous solutlon of small particle powder standards if intenslty lntegratlon is delayed for about 1.8 ms after the start of the discharge. Detectlon limlts are In the low and subparts-per-milllon range for the elements investlgated. Sample preparation typlctrlly involves a 10-15 mlni grinding operatlon in a small mill followed by suspenslon of the powder In Isopropyl alcohol. The method was evaluated with four NBS standard reference materials lncludlng bituminous coal, freeze-dried splnach leaves, wheat flour, and river sediments. Relatlve errors typically range from 5 to 15 % without internal referencing.
Present ;address: Department of Chemistry, University of Ver-
mont, Burlington, VT 05405.
In a recent workshop on trace element analysis sponsored by the U.S. Food and Drug Administration, sample preparation was singled out as the most serious problem facing FDA field laboratories (1). Sample preparation often is the factor limiting analysis time and cost. In addition, analytical accuracy and precision may be degraded through sample loss and contamination. Many sample types occur naturally as solids where the elements of interest are contained in a complex, highly variable, and often tenacious organic or inorganic matrix. Important examples include solid fuels, biological specimens, mineral and ore samples, and agricultural products. Lengthy matrix exchange operations, including high-temperature dry ashing and wet chemical oxidation often are necessary to decompose the matrix and render soluble the inorganic elements of interest. Carbonaceous and siliceous materials may be extremely tenacious and require several hours of sample preparation followed by a determination step requiring only a minute or two (2). These problems have provided considerable impetus for the development of direct methods for the determination of metallic elements in solid, nonconducting samples ( 3 ) .
0003-2700/82/0354-2179$01.25/00 1982 American Chemlcal Society
2180
ANALYTICAL CHEMISTRY, VOL. 54, NO. 13, NOVEMBER 1982
However, when analysis cost and convenience are considered as well as sensitivity and reliability, no single method has demonstrated broad-based applicability. Activation methods, microprobe techniques, and mass spectrometry all require expensive apparatus, and frequently sample handling is complex and time-consuming. X-ray fluorescence has only moderate sensitivity and, in addition, exhibits significant matrix and particle-size effects (4, 5). While furnace techniques with atomic spectrometry have met with some success (6),significant concomitant effects are not infrequent. Particle size and concomitant effects also have frustrated attempts at using high-frequency plasma devices for direct solid, powder analysis (7,8). For most direct solid sampling techniques, the preparation of reliable quantitative standards is difficult and for the microprobe techniques nearly impossible. In a recent series of investigations (9-14), the high-temperature plasmas produced by the capacitive discharge vaporization of thin metal films have been used as efficient atomization cells and excitation sources for atomic emission spectrometry. Clark and Sacks (12)showed that 240-5,4-kV discharges through -200 pg Ag thin films could be used to atomize materials as refractory as ZrC (bp = 5370 K) and that V in small particle (
