SUMMARY OF APPLICATIONS The application of this spectrometric method for the quantitative determination of elemental carbon was in the previously cited ( l a ) analysis of marine sediments. The reproducibility of the method in this application is indicated by the duplicate analyses listed in Table 111. Some analyses of fly ash and atmospheric dust samples have shown that the method is applicable to a wide variety of natural materials. Further, separate experiments have shown that the sensitivity of the method can be significantly improved by employing the ordinate expansion mode of the infrared spectrophotometer.
LITERATURE CITED (1) (a) D. M. Smith, J. J. Griffin, and E. D. Goldberg, Nature (London). 241, 268 (1973); (b) A. M. Swain, Quart. Research, 3, 383 (1973). (2) F. T. Lindgren, G. R . Stevens. and L. C. Jensen, J. Amer. Oil Chem. Soc., 49, 208 (1972). (3) A. Steyermark, "Quantitative Organic Microanalysis," second ed., Academic Press, New York, N.Y.. 1961, p 151. (4) F. Saker, Microchem. J., 16, 145 (1971). (5) C. E. Childs and E. B. Henner, Microchem. J., 15, 590 (1970). (6)R . A. Friedel and L. J. E. Hofer, J. Phys. Chem., 74, 2921 (1970). (7) R . A. Friedel. "Applied Infrared Spectroscopy," D. N. Kendall. Ed., Reinhold, New York, N.Y., 1966, Chap. IO. (8) R. A. Friedel and H. L. Retcofsky, "proceedings of the 5th Carbon Conference," S. Mrozowski, Ed., Pergamon Press, New York. N.Y., 1963, pp 149-165. (9) R. A. Friedel and G. L. Carlson, Fuel, 51, 194 (1972). (10) R. A. Friedel and J. A. Queiser, Bu. Mines Bull., 632, 1966. (11) M. G. Pelipetz and R . A. Friedel. Fuel, 38, 8 (1959).
(12) R . A. Friedel. J. A. Queiser, and H. L. Retcofsky, J. Phys. Chem., 74, 908 (1970). (13) F. S. Karn, R. A. Friedel, and A. G. Sharkey, Jr., Fuel, 51, 113(1972). l i d ) R. A. Friedel and M. G. Pelipetz, J. Opt. SOC.Amer., 43, 1051 (1953). ' R . A. Friedei. "Proceedings of the 4th Carbon Conference," S. Mrozowski. Ed.. Peraamon Press. New York. N.Y.. 1960. DD 321-336. R. A. Friedel, R. A. Durie.'and Y. Shewchyk. Carbon, 5, 559 (1968). J. K. Brown, J. Chem. Soc., 744 (1955). R. A. Friedel, Appl. Opt., 2, 1109 (1963). R . A. Friedel and H. L. Retcofsky, "Spectrometry of Fuels,'' Plenum Press, New York, N.Y., 1970, Chap. 5. V. A. Garten and D. E. Weiss. Aust. J. Chem., 10, 295 (1957). V. A. Garten and D. E. Weiss, "Proceedings of the 3rd Carbon Conference," S. Mrozowski, Ed., Pergamon Press, New York, N.Y.. 1959, p 295. R. A. Friedel and G. L. Carlson, J. Phys. Chem., 75, 1149 (1971). J. S. Mattson and H. B. Mark, Jr., J. Colloid lnterface Sci.. 31, 131 (1969). J. S. Mattson, H. B. Mark, Jr.. M. D. Malbin. W. J. Weber, Jr., and J. C. Crittenden. J. Colloid lnterface Sci., 31, 116 (1969). J. S. Mattson, H. B. Mark, Jr , and W. J. Weber, Jr., Anal. Chern., 41, 355 (1969). F. Tuinstra and J. L. Koenig, J. Chem. Phys., 53, 1126 (1970). D. J. Palmer, J. Colloidlnterface Sci., 37, 132 (1971). H. Harker, J. B. Horsiey, and D. Robson, Carbon, 9, 1 (1971). V. I. Kasatochkin, 0. K. Bordovskiy, N. K. Larina, and K . T. Cherkinskaya, Dokl. Akad. Nauk SSR, 179,690 (1967). R. A. Friedel and A. J. Nawalk, Nature (London), 217, 345 (1968). F. J. Stevenson and K. M. Goh, Geochirn. Cosmochim. Acta, 35, 471 (1971).
RECEIVEDfor review June 7, 1974. Accepted October 7 , 1974. One of the authors (D.M.S.) acknowledges a leave granted by Hope College and the support of National Science Foundation in the form of a Science Faculty Fellowship. This research was supported by a grant from the Environmental Protection Agency.
Inductively Coupled Plasma-Optical Emission Analytical Spectrometry. A Study of Some lnterelement Effects George
F. Larson, Velmer
A. Fassel,' Robert H. Scott,* and Richard N. Kniseley
Ames Laboratory ERDA and Department of Chemistry, Iowa State University, Ames. Iowa 500 10
Investigations of the extent to which certain interelement or interference effects occur in an inductively-coupled plasma are reported. Under conditions normally employed for analytical purposes, it is shown that: a) two solute vaporization interferences often observed in flames are eliminated or reduced to negligible proportions in the plasma; b) increasing concentrations of an easily ionizable element (Na) up to concentrations of 6900 pg/ml exerted an unusually low influence on the observed emission intensities of three selected elements (Ca, Cr, and Cd) of widely differing degrees of ionization. The high degree of freedom from interelement effects of this analytical technique is further documented by the observation that a variety of matrices did not affect the emission intensity of Mo to a significant extent.
During the past decade, inductively-coupled plasmas have emerged as very promising excitation sources for the optical emission determination of trace elements in solution. The ultimate scope of application of this analytical T o w h o m requests for r e p r i n t s should h e directed. Present address, N a t i o n a l Physical Research Laboratory, C o u n c i l for Scientific a n d I n d u s t r i a l Research, Pretoria, S o u t h Africa. 2
238
ANALYTICAL CHEMISTRY, VOL. 47, NO. 2, FEBRUARY
approach will depend to a great extent on its degree of freedom from interelement interactions or interferences. Spectral interferences are not included in the present study, because these interferences are usually strongly dependent on the spectral bandwidth of the spectrometer and the spectral characteristics of the elements. These interferences, therefore, do not necessarily characterize the source alone. The remaining group of interferences may be classified according to several viewpoints ( I ): transport, solute vaporization, vapor-phase, and plasma geometry interferences; specific and nonspecific interferences; and physical and chemical interferences. These various types of interferences are not mutually exclusive in their actions or mechanisms. In this paper we show that: a) two solute vaporization interferences often observed in flames are eliminated or reduced to negligible proportions in the plasma; b) increasing concentrations of an easily ionizable element (Na) up to concentrations of 6900 pg/ml exerted an unusually low influence on the observed emission intensities of three selected elements (Ca, Cr, and Cd) of widely differing degrees of ionization. The high degree of freedom from interelement effects of this analytical technique is further documented by the observation that a variety of matrices did not affect the emission intensity of Mo to a significant extent. 1975
Plasma Properties and Interelement Effects. The presence and degree to which certain interelement effects are observed in inductively-coupled plasmas supported by Ar appear to be sensitively dependent on a number of plasma properties. For example, the two most commonly studied solute vaporization interferences-the depressing effect exerted by increasing concentrations of P043- or Al:’+ ions on calcium free-atom emission or absorption-have been investigated in the inductively-coupled plasma with quite a disparity of results. These variations have been discussed by Fassel ( 2 ) who suggested that differences in the plasma properties may have been responsible. Whereas the plasmas used in the previous studies were similar in some respects-all were radiofrequency excited, inductively-coupled, and Ar supported-one of the notable differences was the plasma configuration. In this context, it is relevant to distinguish between the teardrop (3,4 ) and annular shaped plasmas (2, 5-9). ‘The annular plasma, which appears to be the more desirable analytical source, is readily formed if higher radiofrequencies and a more effective aerosol injection orifice are used than employed by Veillon and Margoshes ( 4 ). If the solution aerosol is efficiently injected into the annular “doughnut hole” shaped plasma, the particles experience a temperature o!’ >6000 K ( 1 0 ) which is about twice that encountered even in the hottest analytically useful combustion flames. This factor, plus the relatively long residence times of the particles in the axial channel (9), results in degrees of atomization that are believed to be exceptionally high for all elements. Once the free atoms are formed, they occur in a plasma whose properties are primarily determined by the Ar that isolates, stabilizes, and sustains the plasma. Since the free atoms reside a t very low concentrations in a chemically inert environment, they may be considered as independently emitting species. Preliminary experimental evidence has shown that the highest population density of analyte ground and excited states are observed along the axial channel. This confinement should lead to a decrease in interference effects produced by a different rate of diffusion of the analyte in the presence of a concomitant (11 ). In view of these desirable environmental conditions, solute vaporization and diffusion interferences should occur to a lower degree than in the commonly used combustion flames. However, changes in the radial distribution of the analyte within the axial channel will affect the measured emission intensities because of the presence of temperature gradients and the efficiency of transfer of the emitted radiat.ion to the detector. In contrast to the above mentioned desirable characteristics of the annular shaped plasma, the teardrop shaped plasma has a relatively poor sample heating efficiency. The expansion of the plasma gas in a direction perpendicular to the exterior surface of the plasma and the high temperature gradients near the surface develop an aerodynamic barrier to the injection of the sample into the plasma (12, 1 3 ) . Consequently, the sample particles will tend to reflect from or pass along the outer surface of the plasma (5, 6 i.
A further distinguishing factor between various inductively-coupled plasmas is the mode in which they are generated. For example, the plasma generator may be a selfexcited oscillator, with the plasma acting as part of the resonant circuit, as used by Boumans and de Boer ( 8 ) .Alternatively, the same type of generator may be used and coupled to the plasma uia an impedance matching network, as utilized in some of our earlier published work (5, 6 ) . A third alternative (91, used in the present study, is based on crystal control of the operating frequency and the use of a tuning-coupling circuit for impedance matching purposes. In this case, the plasma is a less active circuit element. A
relatively high degree of freedom from interference effects has also been observed with a generator of the second type discussed above (14). However, Boumans and de Boer ( 1 5 ) have reported quite different interference effects produced by easily ionizable elements with their facility. The extent to which various interelement effects occur may indeed be dependent on the method of plasma generation, but there are other factors that play a role as well. Thus, the power dissipated in the plasma, the flow velocity of the aerosol carrier gas, the height of observation, and the viewing field of the optical transfer system, all have an effect.
EXPERIMENTAL FACILITIES AND PROCEDURES R a d i o f r e q u e n c y G e n e r a t o r . T h e apparatus. except as modified for the present study, has been previously described ( 9 ) . A feedback circuit was added t o this facility t o maintain a constant forward power in the transmission line to t h e impedance matching network by controlling the screen voltage of t h e oscillator. T h e a d dition of this circuit was necessitated by changes in the radiofrequency power level produced by fluctuations in the mains voltage. T h e extent to which interelement effects occurred was not affected significantly by t h e presence or absence of the feedback circuit. T h e forward power in the transmission line was 1026 watts (or 1250 watts where indicatedj as measured by a Thruline LVattmeter (Model 43, 2500 H element, Bird Electronic Corp., Cleveland, Ohio). T h e measured reflected power was approximately 10 watts. G a s F l o w System. T h e gas flow system, except as modified for t h e present study, has been previously described (16).An additional pressure regulator (Model 93-250, Harris Calorific Co.. Cleveland, Ohio) was added on t h e Ar manifold. A flow controller (No. 8942, Brooks Instrument Div., Emerson Electric Co.. Hatfield, Pa. 1 was employed on the nebulizer flow only, and no filter was employed. .4 pressure gauge (0-100 psi) was added immediately upstream from t h e nebulizer t o monitor the pressure drop across the nebulizer orifice. Aerosol C h a m b e r . T h e dual tube aerosol chamber (9) was replaced by a simpler Teflon and glass chamber. T h e pneumatic nebulizer ( 1 6 ) was attached t o a 125-mm Teflon portion t h a t had an i.d. tapering from 28 t o 18 mm. T h e Teflon portion was connected tu a 18-mm i.d. glass tube about 126 m m long. T h e simpler chamber reduced the clean-out time between samples a n d also decreased the magnitude of several of the interferences (CJa--POIand Ca-AI) discussed later in this paper. T h e Ar flow rates were: 12 I./ min coolant and 1.0 I./min (or 1.3 l./min where indicated) aerosol carrier. O p t i c a l System. The emission from t h e plasma was focused by a 16-ern focal length X 5-cm diameter plano-convex, fused quartz iens positioned a t 30.2 em (twice t h e focal length a t 303.4 nm) from t h e slit. T h e center of t h e plasma was a t 60.4 cm from the slit. Fixed 15 M entrance and exit slits were employed. T h e entrance slit height was masked to 4 nim. P r e p a r a t i o n of Solutions. T h e Ca, Cr, Cd, and hlo analyte solutions were prepared by dissolving reagent grade CaCO:I, Cr metal, CdO, or ( N H d ) & f o O l in dilute HC1. T h e Na concomitant solution was prepared from NaC1. T e n volume percent of concentrated HC1 was added to all solutions so t h a t any acid effects would not bias t h e results. Phosphorous was added as reagent grade H:{POa iS5%) in the Ca-POd system. For t h e study of the Ca-AI system, AI(NO.{)i * 6H20 or AIC1,I was employed. For the studj- of the effect of various concomitants on Mo emission, the concomitants were added as solutions of reagent grade chlorides ( K , N a ) or as solutions of the metal (Al, Cu, Zn) in dilute HC‘1. R e l a t i v e I n t e n s i t y M e a s u r e m e n t s . Intensity d a t a were obtained by peaking the monochromator on t h e line and integrating t h e signal for 24 seconds. T h e signal from t h e blank was then subtracted to yield t h e net relative intensity. T h e concomitant blanks did not differ from the distilled water blank (within 1% of t h e background signal) except for t h e N a and AI which contained a measurable residue of Ca.
RESULTS A N D DISCUSSION The Ca-P04 and Ca-A1 Solute Vaporization Interference Systems. In view of the disparity of results so far
ANALYTICAL CHEMISTRY, VOL. 4 7 , N O . 2, FEBRUARY 1975
239
-> - t 3
x
CoI4227nn C a n 393 4nm
-t
8OL loo
MOLAR RATIO (H3W4/Co)
r-*-‘.-:
F
80,-
Figure 1. Effect of H3P04 on Ca emission intensity at 20 m m above load coil (0.5 pmol/ml Ca) 80
reported on the Ca-P04 and Ca-A1 solute vaporization interference systems, it is of interest to evaluate these interferences in a facility specifically assembled for analytical purposes (9) and operated under conditions used for analytical purposes. Ca-PO4 System. The Ca-P04 solute vaporization interference has been attributed to the formation of a refractory compound, e.g., CazPz07 or Ca3(P04)2, whose greater thermal stability leads to a reduced efficiency of free-atom formation (17-19). In the inductively-coupled plasma, Greenfield et al. ( 7 )reported an absence of the depression effect up to P043--/Ca2+molar ratios of 4. Wendt and Fassel (3) and Veillon and Margoshes ( 4 ) reported enhancements in free-atom absorption in teardrop shaped plasmas. Veillon and Margoshes ( 4 ) also reported an enhancement of about 100% in the calcium free-atom emission a t a P043-/Ca2+ molar ratio of one and even larger enhancements in the calcium ion emission, while Lie and Fassel ( 2 ) reported only small changes in free-atom emission in an annular shaped plasma. The results obtained for the calcium-phosphate system a t an observation height of 20 mm above the load coil with the present facility are shown in Figure 1. In this and in subsequent figures, the net emission intensities of a given species in the absence of an interferent are normalized to 100 arbitrary units a t each observation height. The results of this study are in general agreement with the observations of Greenfield et al. ( 7 ) and Fassel e t al. (2, 3 ) . The precipitous depression and the “knee” in the suppression curve observed in some combustion flames are not detectable, indicating the absence of the classical solute vaporization interference due to compound formation. The slight suppression that is observed a t P043-/Ca2+ approaching 1000 is probably attributable to a transport interference resulting from changes in the physical properties of the solutions. It is important to note that a P043--/Ca2+molar ratio of 1000 here is equivalent to approximately 5 wt % H3P04, which may be considered the analytical equivalent of determining Ca in H3P04. Similar interference curves were obtained at observation heights of 15 u5 mm above the load coil. Ca-AI System. The suppression of Ca free-atom formation in the presence of increasing concentrations of A1 has also been attributed to the formation of a refractory compound (CaA1204,Ca3Al206, etc.) and to the occlusion of Ca in a refractory aluminum oxide matrix (18, 2 0 ) . In combustion flames, with the A1 present in solution as AlCl:95%) in the absence of Al. These rationalizations would not harmonize with experimental observations on the effect of another easily ionizable element (Na) on Ca emission discussed below. Thus, unequivocal interpretations await a better understanding of the physical environment prevailing in the plasma. 1975
c P Ok 120
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Figure 3. Effect of AI on Ca emission intensity in the presence of Na at three heights of observation above load coil (0.5 y m o l / m l Ca; 4600 fig/ml Na)
20rnri
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Figure 5. Effect of Na on Cr emission intensity at three heights of observation above load coil (0.5 p m o l / m l Cr)
CaI4227nn CoG3934nm
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80
1 Na
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Figure 4. Effect of Na on Ca emission intensity at three heights of observation above load coil (0.5 wmol/ml Ca)
T o buffer whatever interactions are occurring through the presence of relatively high concentrations of easily ionizable elements, Na was added at a concentration of 4600 fig/ml (as NaNO3) to another set of otherwise identical solutions. The results obtained for these solutions are shown in Figure 3. The addition of this quantity of Na virtually eliminated the interference effects produced by up to 1350 fig/ml AI (molar ratio Na/A1 = 4). Although higher A1 concentrations produced depressions of both the Ca I and Ca I1 emission a t 15 mm, these depressions were essentially absent a t 20-mm observation height. Interference Effects Produced by Easily Ionizable Elements. Reports in the literature on the existence and degree to which interference effects may occur in the inductively-coupled plasma from changing concentrations of easily ionizable elements are rather limited, considering the possible severity of such effects and the great degree to which they have been observed in other electrically generated plasmas (24-30). Hoare and Mostyn (31) reported that 1000 fig/ml Na did not affect the emission intensity of B and that 10,000 pg/ml Li produced only slight enhancements of atomic lines and slight depressions of ionic lines for an annular shaped inductively-coupled plasma. Kirkbright and associates (32, 33) briefly reported that 50-fold weight excesses of K or Na
CCNLEhTRCT,ZN
Figure 6. Effect of Na on Cd emission intensity at three heights of observation above load coil (0.5 fimol/mi Cd)
did not affect the emission intensities from 100 bg/ml S, 100 figlml P, 100 fig/ml I, 10 fig/ml As, 10 pg/ml Se, and 10 fig/ml Hg in their annular shaped, inductively-coupled plasma. The results of the present study on the interference produced by up to 300 fimol/ml Na (6900 fig/ml) on the emission intensities of atomic and ionic lines of three selected elements of different ionization energies (Ca, Cr, and Cd) are presented in Figures 4-6. The ionization potentials of Ca, Cr, and Cd are 6.11, 6.76, and 8.99 eV ( 3 4 ) ,respectively (with no correction applied for temperature effects on the partition functions). Before attempting some rationalizations of the data plotted in Figures 4 to 6, it is appropriate to note that the additions of relatively high concentrations of Na to the nebulized solution affected the forward and reflected power levels to a very small extent, i.e., without the stabilizing feedback circuit, there was less than a five-watt change in forward power in the transmission line and only an approximate one-watt increase in the reflected power when the solution nebulized into the plasma was changed from deionized water to a solution containing 2.3 wt o/o Na. Under the conditions employed in this study, effective iron excitation temperatures were observed to change only -3 K/watt ( 1 0 ) . Thus, changes in power absorbed by the plasma do not appear to be responsible for the effects observed. As noted
ANALYTICAL CHEMISTRY, V O L . 47, NO. 2, FEBRUARY 1975
241
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2
io - *
HGRIZONTGL
CISPLGCEVENT FiiOhl
CENTER
it^ rn) Figure 7.
Effect of Na on analyte horizontal emission distribution
(Analyte concentration: 0.5 pmol/ml; height of observation: 20 mm above load coil). (-0-) no Na. (- - A - -)6900 pg/ml Na
atmve. the electrons released by the ionization of the increasing concentrations of a n easily ionizable element such as Na, may increase the number density of electrons t o a sufficient degree to suppress the ionization of the analyte species. The trends of the curves plotted in Figures 4 to 6 tend to support this interpretation; z e., for the more easily ionized Ca and Cr species, there is indeed a n enhancement in neutral atom line intensities with increasing concentrations of Na, especially a t a n observation height of 25 mm. If the analyte ionization suppression by the addition of large concentrations of Na were a dominant process, then for an analyte which is relatively easily ionizable (Ca), the large enhancements observed in the atomic lines should be accompanied by much smaller depressions in the ionic lines. For a species such as Cd, which is ionized to a much lesser degree. smaller enhancements in the atomic line and large depressions in the ionic lines would be observed with the suppression of ionization. The existence of some ionization suppression is suggested by the observation that the ionic lines are suppressed to a greater extent than the atomic lines in Figures 4--6 and that the enhancements of both Ca I and Cr I emission are observed high in the plasma (25 m m above the load coil). The combination of a low degree of ionization for Cd and the high excitation potential [5.47 eV ( 3 4 ) ] for the Cd I1 226.5-nm line compared to the relatively high degree of ionization for Ca and the low excitation potential [3.15 eV ( 3 4 ) ] of the Ca I1 393.4-nm line should lead to a much greater effect on the Cd I1 line if changes in effective excitation temperature were a dominant process. The similar behavior of Cd I1 226.5 nm and Ca I1 393.4 nm in Figures 4 and 6 suggests that changes in effective excitation temperatures do not appear to be a dominating factor. We should emphasize that the reported relative intensities in Figures 4-6 represent the effective values within the viewing field of the transfer optics. The importance of this factor is illustrated by the effective horizontal emission profiles a t 20 mm above the load coil plotted in Figure '7. 242
--. - --
i-2-
Figure 8.
:
-22
T-.
Variation of effect of Na on analyte emission intensity
Net intensities of a given species in the absence of Na are normalized to 100 arbitrary units at each height power, and flow rate (Analyte concentration 0 5 pmol/ml Na concentration 6900 wg/ml) (0)1025 watts, 1 0 I /min aero. sol carrier gas (A) 1250 watts 1 0 I /min aerosol carrier gas (0) 1025 watts, 1 3 I /min aerosol carrier gas
The profiles were obtained with the optical transfer system described in Reference 10 and no Abel inversion has been applied. It is seen that the Ca I emission is greatly enhanced by the addition of Na a t a distance of approximately 4 mm from the central axis of the plasma, while the Ca I1 emission is only very slightly enhanced by Na in this region. The Cd I emission is also slightly enhanced off axis by the addition of Na while the Cd I1 emission is not significantly affected in this region. It is quite certain that other factors play a role in the trends of the interference effects plotted in Figures 4 to 6. For example, the concentration of Na employed may have been great enough to produce a transport interference caused by changes in the physical properties of the nebulized solutions. An increase in the forward power to 1250 W had little influence on the interference effects produced by 6900 fig/ml Na on the ionic lines of Ca and Cr and the Cd lines as shown in Figure 8. The enhancements of Ca I and Cr I observed a t 25 mm above the load coil with a forward power of 1025 W were significantly reduced a t the higher power. The effects of increasing the aerosol carrier gas flow to 1.3 l./min on the interference produced by 6900 pg/ml Na are also shown in Figure 8. Rather surprising enhancements for all species are observed a t this flow rate at 15 m m above the load coil. At 20 and 25 mm, the concomitant Na produces enhancements of the atomic lines and depressions of the ionic lines at the higher flow rate. These observations indicate that this variable should be carefully controlled in practice. A definitive interpretation of the magnitude and trend of the analyte line behaviors plotted in Figures 4 t o 8 requires a far more detailed knowledge than is now available of the spatial distributions of analyte free atoms and temperature, of the ionization equilibria prevailing, and on the role played by the Ar sustaining gas. Our present inability to interpret these results in a more definitive manner should
A N A L Y T I C A L CHEMISTRY, VOL. 47, NO. 2 , F E B R U A R Y 1975
Table I. Effect of Concomitants on Emission of 2.5 pg/ml Mo Hrig!it above londrail I m m 15
25
2 rJ
X2O-C2li2
( I f ) , lit0 I
C o n r o n i i t a n t , 2500 c0;m1
A!" I
A k [Ih
\lo I
Ll" Ii
Lla 1
hlo iI
None K Na A1
100
100
100
100
100
100
100
102 107 102"
99
102
97
117
96
105
94 97c
30 30
100
102
98
Zn
100
94 95' 100 100
119 llgc
cu
95 97' 100 100
104
98
* Mo 1390.296 nm. Mo I1 281.615 n m .
D a t a corrected for
103' 100 101
flame
150 150 120
emission by concomitant.
not detract from the fact that at the height of observation (-20 mm) and flow rate (1.0 l./min) selected for excellent powers of detection for a majority of elements, these interferences are small or insignificant for reasonable changes in the concentrations of easily ionizable elements. Effect of Matrix Changes on Analyte Emission. The experimental results summarized above suggest the interesting and potentially very valuable possibility of establishing single analytical curves for the determination of an analyte in a variety of matrices. Documentary evidence that this excitation source, operated under the conditions described in this paper, offers this promise is shown in Table I. These data show that a complete change in the matrix in solution induced a maximum change in signal of only -6% (Na matrix). In contrast, in a high temperature N20-CzH2 flame, the matrix effects ranged from -70 to +50% ( I 1 ). LITERATURE CITED (1) IUPAC Information Bulletin: Appendices on Tentative Nomenclature, Symbols, Units, and Standards-No. 27, Nomenclature, Symbols, Units, and their Usage in Spectrochemical Analysis-ill. Analytical Flame Spectroscopy and Associated Procedures, November, 1972. (2) V. A. Fassel, Proc. 16th Colloq. Spectrosc. lnt., Heidelberg, 1971, Adam Hiiger, London (1972). (3) R. H. Wendt and V. A. Fassel, Anal. Chem., 38, 337 (1966). (4) C. Veillon and M. Margoshes, Spectrochim. Acta, Part E, 23, 503 (1968). (5) G. W. Dickinson, Ph.D. Thesis, Iowa State University, Ames, Iowa, 1969. (6) G. W. Dickinson and V. A. Fassel, Anal. Chem., 41, 1021 (1969). (7) S. Greenfield, I. L. Jones, and C. T. Berry, Analyst (London). 89, 713 (1964). ( 8 ) P. W. J. M. Boumans and F. J. de Boer, Spectrochim. Acta, Part B, 27, 391 (1972). (9) R. H. Scott, V. A. Fassel, R. N. Kniseiey, and D. E. Nixon, Anal. Cbem., 46, 75 (1973).
(10) D. J. Kalnicky. R. N. Kniseley, and V. A. Fassel. submitted to Spectrocbim. Acta, Part B. 11) A. C. West, V . A. Fassel, and R. N. Kniseley, Anal. Chem., 45, 1586 (1973). 12) M. Riemann in "Emissionspektroskopie," R. Ritschl and G. Holdt, Ed., Akademie-Verlag, Berlin, Germany, 1964, p 173. 13) R. Woodriff. Appl. Spectrosc., 22, 207 (1968). 14) R. K. Winge, V. A. Fassel, R. N. Kniseley, and W. L. Sutheriand, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, March 1974, No. 433. 15) P. W. J. M. Boumans and F. J. de Boer, submitted to Spectrochim. Acta, Part B. (16) R. N. Kniseley, H. Amenson. C. C. Butler, and V. A. Fassel, Appl. Spectrosc., 28, 285 (1974). (17) V. A. Fassel and D. A. Becker, Anal. Chem., 41, 1522 (1969). (18) R. Herrmann, C. Th. J. Alkemade, and P. T. Gilbert, "Chemical Analysis by Flame Photometry." Interscience. New York, N.Y., 1963. (19) S. Fukushima, Mkrochim. Acta, 1959, 596. (20) C. Th. J. Alkemade, Anal. Cbem., 38, 1252 (1966). (21) M. Servigne and M. Guerin de Montgareuil, Chim. Anal., 36, 115 (1954). (22) R. E. Popham and W. G. Schrenk, "Developments in Applied Spectroscopy," E. L. Grove and A. J. Perkins, Ed., Plenum Press, New York, N.Y., Vol. 7A, 1969, p 189. (23) C. Th. J. Alkemade and M. H. Voorhuis, Z.Anal. Chem., 163, 91 (1968). (24) K. Kitagawa and T. Takeuchi, Anal. Chim. Acta, 60, 309 (1972). (25) S. Murayama, H. Matsuno, and M. Yamamoto, Spectrochim. Acta, Part B, 23, 513 (1968). (26) S. Murayama, Spectrochim. Acta, Part E, 25, 191 (1970). (27) W. Tappe and J. van Calker, Z. Anal. Cbem., 198, 13 (1963). (28) H. Kawaguchi, M. Hasegawa. and A. Mizuike, Spectrochim. Acta, Part E, 27, 205 (1972). (29) S. E. Valente and W. G. Schrenk, Appl. Spectrosc., 24, 197 (1970). (30) H. Schirrmeister, Spectrochim. Acta., Part E, 23, 709 (1968). (31) H. C. Hoare and R. A. Mostyn, Anal. Chem., 39, 1153 (1967). (32) G. F. Kirkbright, A. F. Ward, and T. S. West, Anal. Chim. Acta, 62, 241 (1972). (33) G. F. Kirkbright, A. F. Ward, and T. S. West, Anal. Chim. Acta, 64, 353 (1973). (34) W. F. Meggers, C. H. Corliss, and B. F. Scribner, "Table of SpectralLine Intensities," Part 1, NBS Monograph 32, Washington, D.C., 1961.
RECEIVEDfor review April 11, 1974. Accepted October 23, 1974.
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