Anal. Chem. 1s84, 56, 2534-2537
2534
hand, CL in oriented systems like micelles and vesicles is very attractive in the viewpoint of analytical chemistry because there is much possibility of enhancing quantum efficiency or energy transfer efficiency and because they permit the use of CL reagents and sensitizers insoluble in water. Registry NO. SOz, 7446-09-5; HzS, 7783-06-4;flavin monoTween 20,9005-64-5; nucleotide, 146-17-8;Tween 85,9005-70-3; Tween 40,9005-66-7; Tween 60,9005-67-8; Tween 80,9005-65-6. LITERATURE CITED (1) Krug, E. C.; Frlnk, C. R. Sclence 1983, 221,520-525. (2) Streets, D. 0.; Knudson, D. A.; Shannon, J. D. Envlron. S d . Techno/. 1983, 17. 474A-485A. (3) Dasgupta, P. K. Anal. Chem. 1981, 53,2084-2087. (4) Rlgo, A.; CherMo, M.; Argese, E.;Vlglino, P.; Dejak, C. Analyst (London) 1091, 106,474-478. (5) Lambert, J. L.; Chejlava, M. J.; Beyad, M. H.; Paukstells, J. V. Talanta 1982, 29, 37-40. (6) Ramasamy, S. M.; Mottola, H. A. Anal. Chem. 1982, 54,283-286. (7) Blzluk, M.; Kozlowskl, E.; Balulescu, G. E. Anal. Lett. 1981, 14, 1377- 1389. (8) Marshall, G.; MMgley, D. Anal. Chem. 1982, 54, 1490-1494. (9) Bhatt, M. A.; Gupta, V. K. Analyst (London) 1983, 108, 374-379. (10) West, P. W.; Gaeke, 0. C. Anal. Chem. 1056, 28, 1816-1819. (11) Stevens, R. K.; Hodgeson, J. A. Anal. Chem. 1973, 45,443A-449A. (12) Fontijn, A. I n “Modern Fluorescence Spectroscopy”; Wehry, E. L., Ed.; Plenum Press: New York, 1976; Vol. 1, pp 159-192. (13) Stauff, J.; Jaeschke, W. Afmos. Envlron. 1975, 9 , 1038-1039. (14) Jaeschke, W.; Stauff, J. Ber. Bunsenges. Phys. Chem. 1978, 82, 1180- 1184. (15) Melxner, F. X.; Jaeschke, W. A. Int. J. Envlron. Anal. Chem. 1981, 10,51-67. (16) Yamada, M.; Nakada, T.; Suzukl, S. Anal. Chlm. Acta 1983, 147, 401-404.
(17) MukerJee,P.; Mysels, K. J. “Critical Micelle Concentrations of Aqueous Surfactant Systems”; NSRDS-NBS-36, Washington, DC, 1971. (18) Yarmchuk, P.; Welnberger, R.; Hlrsch, R. F.; Cline Love, L. J. Anal. Chem. 1982, 54,2233-2238. (19) Armstrong, D. W.; Stine, G. Y. J. Am. Chem. SOC. 1983, 105, 2962-2964. (20) Dorsey, J. G.; DeEchegaray, M. T.; Landy, J. S. Anal. Chem. 1989, 55,924-928. (21) Cline Love, L. J.; Skrllec, M. Int. Lab. 1981, 50-55. (22) Slngh, H.; Hinze, W. L. Anal. Lett. 1982, 15,221-243. (23) Nlkokavouras, J.; Vassilopoulos, G.; Paleos, C. M. J . Chem. Soc., Chem. Common. 1981, 1082-1083. (24) Shinkal, S.; Ishlkawa. Y.;Manabe, 0.; Kunitake, T. Chem. Lett. 1981, 1523-1526. (25) Paleos, C. M.; Vassllopoulos, G.; Nlkokavouras, J. J. fhofochem. 1082. ... -, 18. ., 327-334. - -. - - .. (26) Yamada, M.; Suzukl, S. Anal. Lett. 1984, 17, 251-263. (27) Blrks, J. W.; Kuge, M. C. Anal. Chem. 1080, 52,897-901. (28) ASTM D 1609-80. (29j Huss, A., Jr.; Lim, P. K.; Eckert, C. A. J. Phys. Chem. 1982, 86, 4224-4228, (30) Stauff, J.; Jaeschke, W. 2.Naturforsch., 8 1978, 338,293-299. (31) Pearse, R. W. B.; Gaydon, A. G. “The Identification of Molecular Spectra”, 4th ed.; Chapman and Hall: London, 1976; pp 297-298. (32) Su, F.; Bottenhelm, J. W.; Thorseil, D. L.; Calvert, J. G.; Damon, E. K. Chem. Phys. Lett. 1977, 49, 305-311. (33) Turro, N. J.; Alkawa, M. J. Am. Chem. SOC. 1980, 102,4866-4870. (34) Deguchl, K.; Mino. J. J. Colloid Interface Scl. 1978, 65, 155-161. (35) Nakashima, N.; Asakuma, S.; Kunltake, T.; Hotani, H. Chem. Lett. 1984, 227-230. (36) Fendler, J. H. “Membrane Mimetic Chemistry”; Wlley-Intersclence: New York, 1982; pp 158-183. (37) Donkerbroek, J. J.; Gooljer, C.; Velthorst, N. H.; Frei, R. W. Anal. Chem. 1982, 54,891-895.
RECEIVED for review March 16,1984.Accepted June 4,1984.
Fly Ash Analysis by Complementary Atomic Absorption Spectrometry and Energy Dispersive X-ray Spectrometry Thomas E. Murphy* and Phyllis A. Christensen
Ash Grove Cement Company, Research Lab, 640 Southwest Blvd., Kansas City, Kansas 66103 Roger J. Behrns and Douglas R. Jaquier
Ash Grove Cement Company, Louisville, Nebraska 68037
Gross errors may be encountered In the flame atomlc absorption determlnatlonsof the major oxldes In fly ash If matrlx and background differences are not resolved. Sets of fly ash reference materlals are not available. Sample-standard dlfferences have been obvlated by means of llthlum metaborate fuslon of fly ash and selected NBS reference materlals and the subsequent volumetrlc comblnatlon of the dllute nltrlc acld solutions of the reference materlals. Fly ash data thus generated have been verlfled by energy dlsperslve X-ray analysls, and a llmlted use set of fly ash reference materlals for rapld X-ray analysls of fly ash has resulted.
During recent years, fly ash has gained much attention from the construction industry as a useful and increasingly important raw material (1, 2 ) . Estimated power plant ash production for 1982 was 65.41 million tons, and utilization was 13.55 million tons. This makes it the fourth most abundant solid mineral, ahead of Portland cement and iron ore (3). Once considered a nuisance waste product as well as a disposal 0003-2700/84/0356-2534$01.50/0
problem, fly ash is now recognized as a valuable substance which confers certain desirable characteristics in its many applications (4, 5). Useful qualities of a fly ash may be dictated by its chemical analysis, and this may vary widely throughout the country, depending on the coal type (6, 7). ASTM has attempted to classify fly ash by type, according to the sum of SiOz,A1203, and Fez03 (elements expressed as oxides for convenience). Under this scheme, a fly ash with a total of these three oxides 170% may be termed either a “class F” or a “class C” fly ash. Those below 70% and above 50% are class C fly ashes (8). Other important considerations are the content of NazO, KzO, and SOB. The amounts of CaO and MgO present are generally of secondary importance except as possible indicators of carbonation and hydration potential (9). CaO and MgO are also utilizable for analytical purposes, since the basicity of the ashes may be measured by titration and various chemical relationships may be derived (10). Extensive claims regarding the performance and utility of a fly ash have been made (11,12),and often this is correlated with chemical compositions (13). The physical enhancements 0 1984 American Chemlcal Society
ANALYTICAL CHEMISTRY, VOL. 56, NO. 13, NOVEMBER 1984
attributed to the use or incorporation of fly ash are beyond the scope of this paper. Fly Ash Analysis by Atomic Absorption: Sample Preparation Difficulties. The routine determination of the major elemental composition of fly ash in large numbers of samples presents several challenges. NBS or commercial standard fly ash sets are not yet generally available. Fly ash is not completely soluble in the common mineral acids, and the routine use of perchloric acid, hydrofluoric acid, and aqua regia with the attendant hazards may not be acceptable t o some workers. Furthermore, these fly ash dissolution techniques tend t o be quite lengthy and involved (14, 15). The ordinary fusion and sintering methods are too tedious and time consuming for processing the large numbers of samples of interest in this laboratory. Sealed tubes and bombs are also time-intensive (16). Loss on ignition data is usually a part of a fly ash analysis, as with most mineral analyses, but for fly ash, oxidation of iron may c a w misleading changes in this value. For all of the reasons presented above, a total major oxides analysis of fly ash approaching 100% presents a challenge. This paper presents an adaptation of the lithium metaborate-graphite crucible fusion method of flame atomic absorption sample preparation of Ingamells (17) and Crow and Connolly (18). Atomic absorption sample matrix dissimilarities and gross background effects are resolved by means of a novel method of fused NBS mineral standard preparation which involves volumetric standard solution combinations made by buret or pipet. Results are verifiable by energy dispersive X-ray. Major constituents determined by flame atomic absorption in many diverse samples of fly ash, expressed as oxides, were Si02, A1203,Fe203, CaO, MgO, NazO, and KzO. The minor components of fly ash, exclusive of the alkalies, such as Ti, Mn, and Sr were not determined, nor were the trace elements. Studies involving the minor and trace Constituents of fly ash may be found throughout the literature (19). The determination of the major components of fly ash by atomic absorption is often difficult due to instrumental limitations. Following the routine atomic absorption determination of the major elements present in approximately 100 fly ash samples, seven of these were selected as potential limited-use reference materials for energy dispersive X-ray. The objective was to develop rapid and direct methods for the listed oxides first for atomic absorption and second for X-ray. X-ray data displayed a linear relationship to the atomic absorption results, and this correlation may be used for instrument calibration. EXPERIMENTAL SECTION Reagents and Materials. Dolomitic Limestone 88a, Opal Glass 91, and Bauxite 69a were obtained from the National Bureau of Standards, Washington, DC. ACS reagent grade nitric acid and lanthanum oxide were used. Lithium metaborate, ACS grade, was obtained from G. Frederick Smith Co., Columbus, OH (catalog no. 610). Graphite crucibles were obtained from Spex Industries, Inc., Metuchen, NJ. All atomic absorption solutions were prepared in deionized water. W. R. Grace “DDA-7”grinding aid was used in preparing briquets for energy dispersive X-ray. Apparatus. An Instrumentation Laboratory Model 251 double-beam atomic absorption instrument and standard operating parameters were utilized throughout this work. A Lindberg “hevi-duty” muffle furnace type 51232 was used for fusions. An energy dispersive X-ray fluorescence system was used to verify the fly ash analyses made by atomic absorption. This consisted of the EDAX International, Inc. PV9500 spectrometer with rhodium target X-ray tube and PV9100 computer and spectrum analyzer. Output is through a color monitor and printer. Analytical parameters were 20 kV and 100 HA with vacuum path and analysis time of 100 live s. A Texas Instruments Programmable 59 calculator with an accompanying PC-1OOC printer and program was used to calculate
2535
z 0
4 c
LT c
6 0
Bs
20
4 4
X-RAY INTENSITIES
Figure 1. Flame atomic absorption percentage concentration vs. X-ray intensities for fly ash standards.
linear regression best fit lines and correlation coefficients for graphs of Figure 1. A tungsten Bleuler mill was used for X-ray sample preparation. A hydraulic motor driven briquetting press, model 4451, from Harry W. Dietert Co. was used. Atomic Absorption Solutions. Samples and standards were prepared in exactly the same manner: 0.2500 g of each and 0.4000 g of lithium metaborate were combined in a graphite crucible. A small glass rod was used to mix the sample and fusing material in the crucible. Crucibles were first placed in the opening of the muffle furance with the door slightly ajar to protect against sudden release of gases from the sample and possible loss of material. Later the molten mixtures were carefully rotated to ensure thorough mixing of samples with fluxing agent, and the crucibles were then placed in the center of the 950 OC muffle furnace. When the fluxed beads appeared to be homogeneous, each was carefully poured while still molten into a 250-mL poly(propy1ene) beaker containing 70-80 mL of 1:24 nitric acid. This was done while the nitric acid was magnetically stirred. Graphite crucibles were inspected to ensure complete transfer of the charge. After 7-10 min with stirring, dissolution is complete for most samples. (For samples and standards especially high in aluminum oxide and silicon dioxide, it was sometimes necessary to warm samples in order to obtain complete solution. This was accomplished by placing the poly(propy1ene) beaker in glass weighing dishes containing water and heating on a combination hot plate magnetic stirrer.) Cooled solutions were filtered through rapid filter paper to remove graphite particles and diluted to 500 mL. X-ray Briquets. Fly ash samples were prepared for X-ray analysis by grinding in a Bleuler mill for 3 min with a grinding aid. Powdered samples were pressed into 32-mm briquets approximately 7 mm thick using powdered boric acid as a protective backing. The automatic hydraulic sample press maintained 20000 psi for 60 s. Prepared sample briquets were analyzed for 100 live s by using 20 kV and 100 HA. The intensities of the selected elemental lines were calculated against preestablished curves. The X-ray gross intensities from each run were referenced against a glass reference standard and saved on a disk. Background, matrix, and special interelement correction techniques were deliberately ignored in order to determine the practical limits
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ANALYTICAL CHEMISTRY, VOL. 56, NO. 13, NOVEMBER 1984
Table I. Comparison of Typical Fly Ash Major Oxides with Those Present in Selected NBS Reference Materials
Si02 A1203
Fly Ash" typical range
NBS Bauxite
34.00-48.50 15.40-23.67 5.51-9.91 7.73-24.34 2.38-8.80
Dolomitic Limestone
69a
NBS Opal Glass 91
6.01 55.00 5.82 0.29 0.02
