Volume 10 - Materials Characterization Part 2 pdf

Inductively Coupled Plasma Atomic Emission Spectroscopy Lynda M. Faires, Analytical Chemistry Group, Los Alamos National Laboratory References 1. S. Greenfield, I.L. Jones, and CT. Berry, Analyst, Vol 89, 1964, p 713 2. R.H. Wendt and V.A. Fassel, Anal. Chem., Vol 37, 1965, p 920 3. S.R. Koirtyohann, J.S. Jones, and D.A. Yates, Anal. Chem., Vol 52, 1980, p 1965 4. L. M. Faires, B.A. Palmer, R. Engleman, and T.M. Niemczyk, Spectrochim. Acta, Vol 39B, 1984, p 819 5. M.W. Blades, G. Horlick, Spectrochim. Acta, Vol 36B, 1981, p 861 6. L. M. Faires, T.M. Bieniewski, C.T. Apel, and T.M. Niemczyk, Appl. Spectrosc., Vol 37, 1983, p 558 7. J. E. Meinhard, ICP Info. Newslet., Vol 2 (No. 5), 1976, p 163 8. J.E. Meinhard, in Applications of Plasma Emission Spectrochemistry, R.M. Barnes, Ed., Heyden and Sons, 1979 9. S.E. Valente and W.G. Schrenk, Appl. Spectrosc., Vol 24, 1970, p 197 10. H. Anderson, H. Kaiser, B. Meddings, in Developments in Atomic Plasma Spectrochemical Analysis, R.M. Barnes, Ed., Heyden and Sons, 1981 11. R.H. Scott, V.A. Fassel, R.N. Kniseley and D.E. Nixon, Anal. Chem., Vol 46, 1974, p 76 12. K.W. Olson, W.J. Haas, and V.A. Fassel, Anal. Chem., Vol 49, 1977, p 632 13. C.T. Apel, T.M. Bieniewski, L.E. Cox, and D.W. Steinhaus, Report LA6751-MS, Los Alamos National La boratory, 1977 14. R.R. Layman and F.E. Lichte, Anal. Chem., Vol 54, 1982, p 638 15. M.W. Tikkanen and T.M. Niemczyk, Anal. Chem., Vol 56, 1984, p 1997 16. D.R. Hull and G. Horlick, Spectrochim. Acta, Vol 39B, 1984, p 843 17. E.D. Salin and G. Horlick, Anal. Chem., Vol 51, 1979, p 2284 18. A.G. Page, S.V. Godbole, K.H. Madraswala, M.J. Kulkarni, V.S. Mallapurkar, and B.D. Joshi, Spectrochim. Acta, Vol 39B, 1984, p 551 19. J.W. Carr and G. Horlick, Spectrochim. Acta, Vol 37B, 1982, p 1 20. T. Ishizuka and W. Uwamino, Spectrochim. Acta, Vol 38B, 1983, p 519 21. R.N. Savage and G.M Hieftje, Anal. Chem., Vol 51, 1980, p 408 22. B. Capelle, J. M. Mermet, and J. Robin, Appl. Spectrosc., Vol 36, 1982, p 102 23. S. Greenfield and D.T. Bums, Anal. Chim. Acta, Vol 113, 1980, p 205 24. A. Montaser, V.A. Fassel, and J. Zalewski, Appl. Spectrosc., Vol 35, 1981, p 292 25. M.H. Abdallah and J.M. Mermet, J. Quant. Spectrosc. Radiat. Trans., Vol 19, 1978, p 83 26. R.M. Barnes, ICP Info. Newslet., Vol 8 (No. 3), 1982, p 171 27. T. Hayakawa, F. Kikui, and S. lkede, Spectrochim. Acta, Vol 37B, 1982, p 1069 28. G. Horlick, Appl. Spectrosc., Vol 30, 1976, p 113 29. G. Horlick, R.H. Hall, and W.K. Yuen, Fourier Transform Infrared Spectroscopy, Vol 3, Academic Press, 1982, p 37-81 30. L.M. Faires, B.A. Palmer, R. Engleman, and T.M. Niemczyk, Proceedings of the Los Alamos Conference on Optics, SPIE Vol 380, 1983, p 396-401 31. L.M. Faires, B.A. Palmer, R. Engleman, and T.M. Niemczyk, Spectrochim. Acta, Vol 39B, 1984, p 819 32. L.M. Faires, B.A. Palmer, and J.W. Brault, Spectrochim. Acta, Vol 40B, 1985, p 135 33. L.M. Faires, B.A. Palmer, R. Engleman, and T.M Niemczyk, Spectrochim. Acta, Vol 40B, 1985, P 545 34. E.A. Stubley and G. Horlick, Appl. Spectrosc., Vol 39, 1985, p 805 35. E.A. Stubley and G. Horlick, Appl. Spectrosc., Vol 39, 1985, p 811 36. L.M. Faires, Spectrochim. Acta, Vol 40B, 1985 37. L.M. Faires, Anal. Chem., Vol 58, 1986 38. G. Horlick, Appl. Spectrosc., Vol 22, 1968, p 617 39. E.A. Stubley and G. Horlick, Appl. Spectrosc., Vol 39, 1985, P 800 40. R.S. Houk, V.A. Fassel, G.D. Flesch, H.J. Svec, A.L. Gray, and C.E. Taylor, Anal. Chem., Vol 52, 1980, p 2283 41. A.R. Date and A.L. Gray, Analyst, Vol 106, 1981, p 1255 42. A.R. Date and A.L. Gray, Analyst, Vol 108, 1983, p 1033 43. R.J. Decker, Spectrochim. Acta, Vol 35B, 1980, p 19 44. P.N. Keliher and C.C. Wohlers, Anal. Chem., Vol 48, 1976, P 333A Inductively Coupled Plasma Atomic Emission Spectroscopy Lynda M. Faires, Analytical Chemistry Group, Los Alamos National Laboratory Selected References • R.M. Barnes, CRC Crit. Rev. Anal. Chem., 1978, p 203 • P.W.J.M. Boumans, Optica Pura Aplicada, Vol 11, 1978, p 143 • P.W.J.M. Boumans, Spectrochim. Acta, Vol 35B, 1980, p 57 • V.A. Fassel and R.N. Kniseley, Anal. Chem., Vol 46, 1974, p 1110A, 1155A • V.A. Fassel, Pure Appl. Chem., Vol 49, 1977, p 1533 • V.A. Fassel, Science, Vol 202, 1978, p 183 • S. Greenfield, Analyst, Vol 105, 1980, p 1032 • J.P. Robin, Prog. Anal. At. Spectrosc., Vol 5, 1982, p 79 • M. Thompson and J.N. Walsh, A Handbook of Inductively Coupled Plasma Spectrometry, Blackie and Son, 1983 Atomic Absorption Spectrometry Darryl D. Siemer, Westinghouse Idaho Nuclear Company General Use • Quantitative analyses of approximately 70 elements Examples of Applications • Trace impurities in alloys and process reagents • Water analysis • Direct air sampling/analysis • Direct solids analysis of ores and finished metals Samples • Form: Solids, solutions, and gaseous (mercury) • Size: Depends on technique used from a milligram (solids by graphite furnace atomic absorption spectrometry) to 10 mL of solution for conventional flame work • Preparation: Depends on the type of atomizer used; usually a solution must be prepared Limitations • Detection limits range from subparts per billion to parts per million • Cannot analyze directly for noble gases, halogens, sulfur, carbon, or nitrogen • Poorer sensitivity for refractory oxide or carbide-forming elements than plasma atomic emission spectrometry • Basically a single-element technique Estimated Analysis Time • Highly variable, depending on the type of atomizer and technique used • Sample dissolution may take 4 to 8 h or as little as 5 min • Typical analysis times range from approximately 1 min (flames) to several minutes (furnaces) Capabilities of Related Techniques • Inductively coupled plasma atomic emission spectrometry and direct current plasma atomic emission spectrometry are simultaneous multielement techniques with a wider dynamic analytical range and sensitivities complementing those of atomic absorption spectrometry. They cost considerably more to set up and require more expert attention to potential matrix interference (spectral) problems Atomic absorption spectrometry (AAS) originated in the 1850s and 1860s (Ref 1, 2). It was recognized that the positions (wavelengths) of the dark lines in the solar spectrum matched those of many of the bright (emission) lines seen in laboratory flames "salted" with pure compounds. It was deduced that the dark lines were caused by the extremely selective absorption of the bright continuum radiation emitted from the inner regions of the sun by free atoms in the cooler, less dense upper regions of the solar atmosphere. The qualitative spectral analysis technique that resulted from this research remains the most important tool for astrophysical research. However, as a routine chemical laboratory analysis technique, AAS was often overlooked in favor of atomic emission techniques until relatively recently. The first important use of AAS as a routine laboratory technique for quantitative analysis dates from a description of a mercury vapor detection instrument in 1939 (Ref 3). This development did not greatly affect the chemical analysis field, because the procedure was useful only for mercury, an element whose physical properties make it a special case. The potential value of AAS as a general-purpose metallic-element analysis method was not realized until 1955, when a more flexible technique was discovered (Ref 4). These instruments combined the two basic components found in most modern spectrometers: a simple flame atomizer to dissociate the sample solutions into free atoms and sealed atomic line source spectral lamps. Early papers stressed the theoretical advantages of absorption as compared to emission methods of spectrochemical analyses; that is, atomic absorption is independent of the excitation potential of the transition involved, and analytical methods based on absorption should be less subject to some types of interferences, making these techniques more rugged. The technique remained largely a laboratory curiosity for a few more years until instrument companies began to manufacture first-generation instruments for routine analytical work. By the early 1960s the practical analytical advantages of AAS over the other spectrochemical methods had become apparent, providing nonspecialists with a simple, reliable, and relatively inexpensive method for trace-metal analyses. Atomic absorption spectrometry is generally used for measuring relatively low concentrations of approximately 70 metallic or semimetallic elements in solution samples. The basic experimental equipment used is essentially the same as that of 30 years ago enhanced by modern electronics, background-correction schemes, and alternate types of atomizers. The predominance of AAS in general-purpose trace-metal analysis has recently been somewhat eclipsed by modern atomic emission spectrochemical methods designed to permit solution analysis. However, its ruggedness and relatively low equipment costs keep AAS competitive. Atomic absorption spectrometry performed using the graphite-tube furnace atomizer usually remains the method of choice for ultra-trace-level analysis. References 1. G. Kirchoff, Pogg. Ann., Vol 109, 1860, p 275 2. G. Kirchoff and R. Bunsen, Philos. Mag., Vol 22, 1861, p 329 3. T.T. Woodson, Rev. Sci. Instrum., Vol 10, 1939, p 308 4. A. Walsh, Spectrochim. Acta, Vol 7, 1955, p 108 Atomic Absorption Spectrometry Darryl D. Siemer, Westinghouse Idaho Nuclear Company Principles and Instrumentation Figures 1 and 2 show the relationship between the flame atomizer versions of AAS and the related techniques of atomic fluorescence spectrometry (AFS) and atomic emission spectrometry (AES). Several features are common to all three techniques. The first is a sample-introduction/atomization system consisting of a sample sprayer (referred to as the nebulizer) and the flame. The flame desolvates, vaporizes, then atomizes (dissociates to free atoms) the fine sample droplets produced by the nebulizer. Next is the monochromator, which isolates a wavelength of light characteristic of a particular quantized transition between electronic energy levels of the outer electrons of the selected analyte element. The third component is the light intensity-to-electrical signal transducer, usually a photomultiplier tube (PMT). Finally, an electronic data-reduction system converts this electrical signal to an analytical response proportional to the concentration of analyte in the sample solution. Fig. 1 Energy-level transitions of the atomic spec trometries. (a) Atomic emission spectrometry. (b) Atomic absorption spectrometry. (c) Atomic fluorescence spectrometry. N*, number of atoms in the excited state; N 0 , number of atoms in the ground state; l 0 , light intensity measured without the analyte present; l, light intensity measured with the analyte present Fig. 2 Comparison of (a) flame atomic emission spectrometry, (b) fl ame atomic absorption spectrometry, and (c) flame atomic fluorescence spectrometry. It should be noted that within typical atmospheric pressure atomizers, the intrinsic width of the absorption/emission lines of the elements are typically from 0.002 to 0.008 nm. A comparison of these linewidths with the approximately 600 nm- wide working range of the spectrometers normally used in atomic spectroscopy indicates that approximately 10 5 resolution elements are potentially available to determine the approximately 100 elements of the periodic table. The relatively high ratio of the number of possible resolution elements to the number of chemical elements (approximately 1000:1) explains why atomic spectroscopic methods tend to be more specific than most other analysis techniques. The ease of applying this intrinsic specificity in actual practice differs substantially among the three types of atomic spectroscopy. In atomic emission spectrometry (Fig. 1a and 2a), the flame serves an additional function not required in AAS or AFS: excitation. To produce the desired signal, hot flame gases must thermally (collisionally) excite a significant fraction of the free atoms produced by dissociation in the atomizer from the relatively populous ground-state level to one or more electronically excited states. The excited atoms emit light at discrete wavelengths corresponding to these differences in energy levels when they spontaneously relax back to the lower states. That is, the instrument "sees" the excited-state population of analyte atoms, not the ground-state population. The ratio of the population of atoms in a thermally excited state to that in a lower energy state follows the Boltzmann distribution; that is, the logarithm of the ratio is directly proportional to the absolute temperature and inversely proportional to the difference in energy between the states. Therefore, the absolute magnitude of emission signals is temperature dependent. At typical atomizer temperatures, only a small fraction of atoms are excited to levels capable of emitting visible or ultraviolet radiation; most remain at or very near to the ground-state energy level. Because flames do not specifically excite only the element of interest, a monochromator able to resolve close lines while maintaining a reasonable light intensity through-put must be used to reduce the probability of spectral interferences. Additional broad band-like light emitted by similarly thermally excited molecular species, for example, OH or CH flame radicals or matrix-metal oxides, complicates isolation of the desired signal from the background. Atomic emission spectrometry usually necessitates scanning the monochromator completely over the analytical spectral line to obtain the background signal values necessary for the calculation of a correct analytical response. Reasonably inexpensive high-resolution monochromators capable of automatic correction of background emission using Snellemans's wavelength modulation system have become available only recently. In atomic absorption spectrometry (Fig. 1b and 2b), radiation from a lamp emitting a discrete wavelength of light having an energy corresponding to the difference in energies between the ground state and an excited state of the analyte element is passed through the atomizer. This light is generated by a low-pressure electrical discharge lamp containing a volatile form of the analyte element. Free analyte atoms within the atomizer absorb source-lamp light at wavelengths within their absorption profiles. The absorption lines have a bandwidth approximately twice as wide as the emission profiles of the same elements in the low-pressure source lamp. In contrast to AES, ground-state (not excited state) atomic populations are observed. The source light not absorbed in the atomizer passes through the monochromator to the light detector, and the data reduction/display system of the spectrometer outputs an absorbance response directly proportional to the concentration of analyte in the sample solution. Absorbance is the logarithm (base 10) of the ratio of the light intensities measured without (I 0 ) and with (I) the analyte atoms present in the light path (absorbance = log I 0 /I). In practice, the intensity of the source lamp is amplitude modulated at a specific frequency to permit subsequent electronic isolation of the "AC" light signal of the lamp from the "DC" light caused by the emission from species thermally excited by the atomizer. DC light is invariant relative to time. Only the relatively highly populated ground-state population of the same element in the atomizer that is in the source lamp can contribute to the signal. Therefore, the analytical response of atomic absorption spectrometers is element- selective and not as sensitive to atomizer temperature variations as that of atomic emission spectrometers. In addition, the electronic lamp modulation/signal demodulation system renders the spectrometer blind to extraneous light sources. The monochromator serves only to isolate the desired analytical line from other light emitted by the one-element source lamp. Consequently, a less sophisticated monochromator suffices in AAS than is usually required for general-purpose AES. The major error signal encountered in AAS is the nonselective absorption or scattering of source-lamp radiation by undissociated molecular or particulate species within the atomizer. Several different types of background correction systems will be discussed later in this article. Atomic fluorescence spectrometry (Fig. 1c and 2c), an emission technique, relies on an external light beam to excite analyte atoms radiatively. The absorption of light from the light source creates a higher population of excited-state atoms in the atomizer than that predicted by the Boltzmann equation at that temperature. Consequently, the absolute sizes of the atomic emission signals detected are larger than those seen in AES experiments performed with the same concentration of analyte atoms within the atomizer. A source-lamp modulation/signal demodulation scheme similar to that applied in atomic absorption spectrometers isolates the atomic fluorescence response from that emitted by thermally excited analyte, flame, or matrix species. Atomic fluorescence spectrometry spectra tend to be much simpler than AES spectra. This is true even when bright continuum light sources, such as xenon-arc lamps, are used instead of line sources for excitation, because only those atomic emission lines originating from energy levels whose populations are enhanced by the initial atomic absorption step can contribute to an AFS response. When line-source excitation lamps are used, this initial excitation step is very selective, and the AFS spectrum becomes extremely simple. Monochromators are often not used; the only concession to spectral isolation is the use of a photomultiplier insensitive to room light (Ref 5). Atomic fluorescence spectrometry has two major sources of error. The first is chemical scavenging or de-excitation (termed quenching) of the nonequilibrium excited-state analyte atom population (that in excess of the thermally excited population) before a useful light signal can be emitted. The magnitude of this error signal depends on the concentration of the quenchers in the gas phase, which depends on the chemical makeup of the sample matrix accompanying the analyte element. Consequently, quenching introduces a potential source for matrix effects in AFS not found in AAS. The second source of error is scatter of the exciting radiation by particulate matter within the atomizer. Some refractory metals, such as zirconium and uranium, if present in high concentrations in the sample, are apt to be incompletely dissociated or even gassified in conventional atomizers. This scatter signal is sometimes compounded with molecular fluorescence emission signals from naturally present gaseous flame species, a condition especially troublesome when continuum-type excitation sources are used. Advantages of Atomic Absorption Spectrometry. During the past 25 years, AAS has been one of the most widely used trace element analysis techniques, largely because of the degree of specificity provided by the use of an analyte-line light source. This reduces the probability of "false positives" caused by matrix concomitants and serves to enhance greatly the reliability of AAS determinations performed on "unknown" samples. A background-corrected atomic absorption instrument is also one of the most reliable, albeit slow, tools available for qualitative analysis. The need for simple monochromators has maintained the cost of AAS equipment well below that of AES instrumentation having similar capabilities. Line-excited AFS has the specificity of AAS as well as other desirable characteristics, such as a greater dynamic range and potentially better detection limits. However, obtaining appreciable improvement over AAS detection capabilities with AFS usually requires more attention to optimizing the optics, atomizer, and electronics of the system. In addition, because correction for "scatter" signals is fundamentally more important and more difficult to accomplish than is background absorption correction in AAS, no flame- or furnace atomizer-based AFS unit is commercially available. Atomic emission spectrometry has found limited acceptance in the instrument market-place. Although most of the better atomic absorption instruments sold during the 1960s and 1970s could be used for flame-excited AES, the instrument requirements for the two techniques are so different that the results achieved using these spectrometers did not reflect the true potential of the method. Only the recent introduction of electrical plasma emission sources, such as inductively coupled plasma (ICP) or direct current plasma (DCP), designed for the routine analyses of solution samples has prompted commercial production of fairly inexpensive and compact spectrometers optimized for AES (see the article "Inductively Coupled Plasma Atomic Emission Spectrometry" in this Volume). However, these instruments remain considerably more expensive than basic atomic absorption spectrometers. Atomic Absorption Spectrometry Sensitivities. The periodic table shown in Fig. 3 lists typical analytical sensitivities obtained using representative atomic absorption spectrometers with either a flame or the more sensitive graphite furnace atomizer. The entries in Fig. 3 represent the magnitude of the atomic absorbance signal expected when a 1-ppm solution of the element is continuously aspirated into a flame atomizer or introduced as a discrete 25-μL aliquot into a graphite furnace. Fig. 3 Typical analytical sensitivities obtained using flame or graphite furnace atomic abs orption spectrometry. (a) Results obtained by Varian Techtron Ltd., Melbourne, Australia. (b) Results obtained by Allied Analytical Systems, Waltham, MA In practice, the performance of reliable analysis requires signal magnitudes ranging from 0.01 to 1.0 absorbance unit. This is a consequence of the signal-to-noise considerations involved in measuring small differences in two relatively large light signals. This rather limited dynamic analytical range often necessitates the concentration or dilution of sample solutions before analysis. The reasons for the extreme differences in AAS sensitivities noted in Fig. 3 can be divided into three basic categories, the first two of which affect AAS, AFS, and AES nearly equally. First, because the number of atoms within the light path at a given time fundamentally determines the instantaneous signal, the mass-based sensitivities in Fig. 3 are biased in favor of the lighter elements. Second, a substantial number of elements do not possess ground-state lines in a region of the spectrum that is accessible with normal spectrometers and to which the gases present within normal atomizers are transparent. Less sensitive alternative analytical lines may sometimes be used, for example, with mercury and phosphorus; for other elements (most of the fixed gases), no good lines are available. Further, many elements possess a multitude of atomic energy states near the absolute ground-state level. These low-lying levels are thermally populated to some degree at the working temperature of the atomizer, which tends to reduce the fraction of analyte atoms available at any one energy level to absorb a specific wavelength of light emitted by the source lamp. This reduces the sensitivity achievable by any atomic spectroscopic technique for many of the transition, lanthanide, and actinide elements. Lastly, none of the atomizers commonly used in atomic absorption spectrometers provides conditions capable of substantially dissociating some of the more commonly encountered forms of some chemically reactive analyte elements. For example, boron forms stable nitrides, oxides, and carbides. No practical adjustment of the operating conditions of any of the conventional atomic absorption atomizers can provide an environment that is simultaneously sufficiently free of nitrogen, oxygen, and carbon to give a favorable degree of boron dissociation. However, the combination of the much higher temperatures and inert gas environments found in electrical plasma AES sources makes boron one of the most sensitive elements determined by modem AES instruments. Reference cited in this section 5. J.D. Winefordner and R. Elser, Anal. Chem., Vol 43 (No. 4), 1971, p 24A Atomic Absorption Spectrometry Darryl D. Siemer, Westinghouse Idaho Nuclear Company Atomizers The sensitivity of AAS determinations is determined almost wholly by the characteristics of the light source and the atomizer, not by the optics or electronics of the spectrometer. Simple, inexpensive AAS instruments have the same sensitivity as more sophisticated models. Because the line-source lamps used in AAS have essentially the same line widths, most of the sensitivity differences noted between instruments can be attributed to differences in the atomizers. Table 1 lists the more important characteristics of the three most common AAS atomizers. The values listed for the dilution factor (Df) represent an estimate of the degree to which an original liquid sample is diluted (or lost) by the time it passes through the optical path of the spectrometer. Furnaces are more sensitive than flame atomizers primarily because the volatilized analyte is diluted with far less extraneous gas. Because the magnitude of an atomic absorption signal is proportional to the number of atoms present within a unit cross section of the light path at a given instant, the product of the dilution factor and the path length of the atomizer (Df × L) provides the best indication of the relative analytical sensitivities expected for elements atomized with equal efficiencies. Table 1 Atomizer characteristics Atomizer Temperature, K Sample volumes, mL Atomizer path length, cm Dilution factor (a) Atomizer path length × dilution factor Air-acetylene flame 2500 0.1-2 10 2 × 10 6 2 × 10 5 Nitrous oxide-acetylene flame 3000 0.1-2 5 1.7 × 10 6 8.5 × 10 6 Graphite furnace 300-3000 0.001-0.05 2.5 0.02 0.05 Quartz tube (hydride generator) 800-1400 1-40 15 0.007 0.1 (a) Dilution factor (Df) assumptions: Flames 20 L/min of fuel/oxidant, 7 mL/min sample aspiration rate (5% actually introduced); furnace maximum furnace diameter of 0.6 cm (0.25 in.), gaseous analyte atom containment efficiency of 30%, 50- L sample aliquot; quartz tube 20- ml. sample, a gas/liquid separation efficiency giving 10% of analyte in the light path within 2 s at signal maximum, 1200 K When the sensitivity figures listed in Fig. 3 are combined with the dilution factor estimates of Table 1 to estimate molar extinction coefficients of gas phase atoms, figures of approximately 10 8 (in the usual units of liters per mole per centimeter) are typical. In conventional spectrophotometry of dissolved molecular species, extinction coefficients for strong absorbers are at best three orders of magnitude lower. This extremely high absorption coefficient enables AAS performed using atomizers with high Df factors to have sensitivities competitive with other analytical techniques. Flame atomizers are usually used with a pneumatic nebulizer and a premix chamber (Fig. 4). The fuel/oxidant/sample droplet mixtures are burned in long, narrow slot burners to maximize the length of the atomization zone within the light path of the spectrometer. The premix chamber is designed to discard the sample droplets produced by the sprayer, which are larger than a certain cutoff size, and to mix the remaining droplets with the fuel and oxidant gases before they reach the burner. [...]... nm Bandpass, nm Flame(d) Aluminum 2 200 309.3 0 .2 N Cobalt 0.5 50 24 0.7 0.1 AO Chromium 0.5 50 357.9 0 .2 N Copper 0 .2 20 324 .7 0 .2 A Magnesium 0 .2 2 28 5 .2 0.5 N Manganese 0 .2 20 27 9.5 0 .2 AO Molybdenum 0.5 50 313.3 0 .2 N Nickel 0.6 60 3 52. 4 0 .2 AO Lead 0.4 40 28 3.3 0 .2 AO Tin 0.8 80 28 6.3 0 .2 N Titanium 2. 5 25 0 364.3 0 .2 N Vanadium 1 100 318.4 0.1 N Tungsten(a) 4 400 25 5.1 0.1 N (a) Samples containing... nm Bandpass, nm Flame(d) Aluminum 2 200 309.3 0 .2 N Cobalt 0.5 50 24 0.7 0.1 AO Chromium 0.5 50 357.9 0 .2 N Copper 0 .2 20 324 .7 0 .2 A Magnesium 0 .2 2 28 5 .2 0.5 N Manganese 0 .2 20 27 9.5 0 .2 AO Molybdenum 0.5 50 313.3 0 .2 N Nickel 0.6 60 3 52. 4 0 .2 AO Lead 0.4 40 28 3.3 0 .2 AO Tin 0.8 80 28 6.3 0 .2 N Titanium 2. 5 25 0 364.3 0 .2 N Vanadium 1 100 318.4 0.1 N Tungsten(a) 4 400 25 5.1 0.1 N (a) Samples containing... trace-element content in H2O2 Element Integration Sample decomposition Delay, s Deposition, s Replicates Mode Integration time, s Tin 5 20 2 Peak height Element Temperature program(a), °C (°F), s 1.5 Spectrometer conditions Step 1 2 3 4 5 6 Wavelength, nm Bandpass, nm Slit width, nm Chromium 100 (21 2) 10 125 (25 5) 15 800 (1470) 15 900 (1650) 10 21 00 (3 810) 0 21 00 (3 810) 10 357.9 1 320 Tin 75 (165) 100 ... 1 320 Tin 75 (165) 100 (21 2) 450 (840) 800 (1470) 21 00 (3 810) 21 00 (3 810) 23 5.5 0.5 160 (a) The time stated for the temperature program indicates the time to ramp to the stated temperature (0 s indicates a rapid temperature increase in . Sample volumes, mL Atomizer path length, cm Dilution factor (a) Atomizer path length × dilution factor Air-acetylene flame 25 00 0. 1 -2 10 2 × 10 6 2 × 10 5 Nitrous oxide-acetylene. oxide-acetylene flame 3000 0. 1 -2 5 1.7 × 10 6 8.5 × 10 6 Graphite furnace 30 0-3 000 0.00 1-0 .05 2. 5 0. 02 0.05 Quartz tube (hydride generator) 80 0-1 400 1-4 0 15 0.007 0.1 (a) Dilution. Vol 36, 19 82, p 1 02 23 . S. Greenfield and D.T. Bums, Anal. Chim. Acta, Vol 113, 1980, p 20 5 24 . A. Montaser, V.A. Fassel, and J. Zalewski, Appl. Spectrosc., Vol 35, 1981, p 29 2 25 . M.H. Abdallah