900
Anal. Chern. 1904, 56,908-913
Newport News station, and were collected on different days over a period of 2 months during the summer of 1982. All samples were aspirated directly without any processing. The results obtained are summarized in Table V. Table V(a) also includes the data obtained with the colorimetric method for comparative purposes. In almost all cases, the DCP data are higher than the colorimetric data. This is due to the ability of the DCP to excite particulate and other forms of phosphorus and silica. The colorimetric method is only suitable for orthophosphate and reactive silica. This work demonstrates the suitability of DCP emission for atomic spectroscopic measurements of nonmetals and metalloids in complex sample media. The demonstrated element selectivity capability renders this approach suitable as a detector for various separation systems and, in particular, for element speciation studies.
ACKNOWLEDGMENT The author thanks Karen 0. Williams and Harold G. Boston for their assistance in portions of this work. Registry No. As, 7440-38-2; B, 7440-42-8; C, 7440-44-0; P, 7723-14-0; Se, 7782-49-2; Si, 7440-21-3; PO4, 14265-44-2; Pz07, 14000-31-8; HZO, 7732-18-5.
LITERATURE CITED Rippetoe, W. E.; Johnson, E. R.; Vickers, T. J. Anal. Chem. 1975, 47, 436. Urasa, I. T. Ph.D. Thesls, Colorado State University, Fort Coillns, CO, 1977. Skogerboe, R. K.; Urasa, I.T Appl. Spectrosc. 1978, 32, 527. Gilbert, T. R.; Stacey, G. M. I n “Applications of Plasma Emisslon Spectrochemistry”; Barnes, R. M., Ed.; Heyden: Philadelphia, PA, 1979. Bankston, D. C.; Humphrls, S. E.; Thompson, G. I n “Applications of Plasma Emission Spectrochamlstry”; Heyden: Philadelphia, PA, 1979; p 90.
Griffin, E.; Salvolainen, A. I n “Application of Plasma Emission Spectrochemistry“; Haydan: Philadelphia, PA, 1979; p 119. Wojciak, J.. Jr. I n “Application of Plasma Emission Spectrochemistry”; Heyden: Phlladelphia, PA, 1979; p 134. Smith, R. G. I n “Metallic Contaminants and Human Health”; Lee, D. K., Ed.; Academic Press: New York, 1972; p 158. Holak, W. Anal. Chem. 1989, 4 7 , 1712. Bejmuk, A. M.S. Thesis, Colorado State University, Fort Collins, CO, 1977. Robbins, W. B.; Caruso, J. A. Anal. Chem. 1979, 51, 889A. Woinik, K. A.; Fricke, R. L.; Hahn, M. G.; Caruso, J. A. Anal. Chem. 1981, 53,1030. Matsumoto, K.; Fuwa, K. Anal. Chem. 1982, 54, 2012. Dedina, J. Anal. Chem. 1982, 54, 2097. Van Loon, J. C. Anal. Chem. 1979, 51, 1139A. Chau, Y. K.; Wong, P. T. S.; Goulden, P. D. Anal. Chem. 1975, 47, 2279. Goulden, P. D. “Environmental Pollution Analysis”; Heyden: Philadeiphia, PA, 1978. Grabinski, A. A. Anal. Chem. 1981, 53,966. Iverson, D. G.; Anderson, M. A.; Holm, T. R.; Stanforth, R. R. Environ , Sci. Technol. 1979, 13, 1491. Riccl, 0. R.; Shepard, L. S.; Cobs, G.; Hester, N. E. Anal. Chem. 1981, 53,810. “Standard Methods for the Examlnation of Water and Wastewater”; 14th ed.; American Public Health Association: Washington, DC, 1975. Pau, J. C. M.; Pickatte, E. E.; Kolrtyohann, S. R. Analyst (London) 1972, 97, 860. Rossi, G.; Soldanl, G. Analyst (London) 1972, 97, 124. Vigler, M. S.;Strecker, A.; Varnes, A. Appl. Spectrosc. 1979, 32, 60. Prager. M. J.; Seitz, W. R. Anal. Chem. 1975, 47, 148. Uchida, H.; Shimoishl, Y.; Toei, K. Environ. Sci. Technol. 1980, 14, 541. “Tables of SpectraCLina Intensities”; U S . Department of Commerce, National Bureau of Standards: Washington, DC, 1975; NBS Monograph 145, Part I. “Massachusetts Institute of Technology Wavelength Tables”; The M.I.T. Press: Cambrldge, MA, 1969.
RECEIVED for review July 14,1983. Resubmitted January 23, 1984. Accepted February 6,1984. This work was supported by a grant from the US.Environmental Protection Agency: Grant Number R808676010.
Analysis of Iron-Base Alloys by Low-Wattage Glow Discharge Emission Spectrometry Kazuaki Wagatsuma and Kichinosuke Hirokawa*
The Research Institute for Iron, Steel, and Other Metals, Tohoku University, Sendai, Japan
Several Iron-base alloys were investigated by low-wattage glow dlscharge emisslon spectrometry. The emlsslon intensity principally depended on the sputtering parameters of constituent elements in the alloy. However, in the case of chromium, stable and firm oxldes formed on the surface influencing the yield of ejected atoms. This paper discusses the relatlon between the sputtering parameters In Fe-NI, Fe-Cr, and Fe-Co alloys and their relative emission intensities. Additlonaiiy, quantitative analysis was performed for some ternary iron-base alloys and commercial stainless steels with the callbratlon factors of binary alloy systems.
The states of real surfaces seriously influence the physical and/or chemical properties of materials such as corrosion, oxidation, friction, and so on. It is an important to determine the chemical compositions of the surfaces as accurately as possible.
Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), or secondary ion mass spectroscopy (SIMS) are useful tools for the study of surfaces. However, these methods need an ultrahigh vacuum system and their use presents some complex problems. Optical emission spectrometry by glow discharge lamp, suggested by Grimm (I,2), has some advantages for the research of real surfaces. It is an accurate and reliable analytical technique; in addition, glow discharge spectrometry (GDS) has the following features: (a) as the sample introduction into the plasma is based upon the cathode sputtering (3),the thermal effects resulting in melting or vaporization, which appear in the arc and spark spectrometric sources (41, are absent; (b) the emission lines are sharp and the self-absorption effect is small compared to the other light sources (5) because the GDS is operated under reduced pressures. By use of a sputtering mechanism, the surface analysis has been carried out in several earlier works of the GDS (6-8). However, as the cathode sputtering in an abnormal glow
0003-2700/84/0356-0908$01.50/00 1984 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 56, NO. 6, MAY 1984
Table I. Instrumentation and Operating Conditions spectrometer photomultiplier power supply spectral band-pass base pressure filled gas pressure
Model 808 (Hitachi, Ltd., Japan) R-446 (Hamamatsu Photonics, Ltd., Japan) Model PAD 1K-0.2L (Kikusui Electronics Corp., Japan) constant current mode 0.1 nm 4.0-1.3 Pa argon (special grade for vacuum spectrometry) 4.0 x 10' Pa
discharge region (9) is employed in these conventional studies, the sputtering rate is rather high (the population and the mean kinetic energy of primary ions are high). Accordingly, the resolving power in depth is limited, and much deposit is accumulated around the anode so that it is difficult to keep constant plasma conditions. On the other hand, mild sputtering conditions are provided in a low-wattage glow discharge even though the emission intensity is weak. We measured and analyzed the emission spectra of several iron-base alloy systems using the low power GDS. Applications of the GDS to the surface analysis of steels or iron-based alloys have been done by some investigators (10); however, in most cases, the analytical objects were limited only to thick layers such as coated films, galvanized films, etc. Our interests are focused onto the sputtering characteristics especially in Fe-Ni, Fe-Cr, and Fe-Co alloys. In this paper, the results on several iron-based binary and ternary alloys are reported and the quantitative analyses of alloyed elements in these samples are also discussed.
EXPERIMENTAL SECTION Our glow discharge lamp was made according to the original model reported by Grimm (1). The inner diameter of the hollow anode was 8.0 mm and the distance between the anode and cathode was adjusted to be 0.4-0.6 mm. The instruments for our experiment and their operating conditions are summarized in Table I. The series of iron-base alloys was received from the Iron and Steel Institute of Japan (standard samples for X-ray fluorescence analysis). The surfaces were polished with emery paper (no. 600 to no. 1500) and finished to mirror-faces with emery cloth and then predischarge for 3-5 min at about 550 V (20 W) was carried out to remove contaminations and initial surface oxides.
RESULTS AND DISCUSSION Measurement by the GDS. As already discussed (111,the intensity ratio (I,/Ib) of resonance lines for two different elements (a and b) is given in eq 1 if the following major assumptions are satisfied (a) the energy levels of each excited state are approximately equal; (b) the degree of the self-absorption for one emission line is comparable to that for the other line
Ia/Ib = R(N,/Nb) R = constant (1) where N,/Nb is the atomic ratio for two different elements in the plasma. In the above assumptions, by selecting the proper pairs of emission lines which have almost the same excited levels, the first condition can be fulfilled; however, attention must be given to the second condition. In order to estimate the influence of the self-absorption, it is convenient to examine the intensity ratio of two lines of the same element. If the ratio of these intensities is independently constant of the input power, the self-absorption is not significant. In addition, it is a good method to study whether eq 1is realized over the wide concentration range or not. With these conditions satisfied, the intensity ratio is not influenced by the excitation temperature and is directly
909
Table 11. Selected Emission Lines of Each Element and Their Assignments
element
wavelength, nm
assignment lower level upper level
iron
344.1 344.099 (3.65 eV) 344.061 5P, (3.60 eV) nickel 339.3 3D, (3.67 eV) 3F,(3.66 eV) 341.5 2P,(3.54 eV) 352.5 chromium 360.5 7P, (3.44 eV) 359.3 'P, (3.45 eV) cobalt 340.5 4F,/z(4.07 eV) 345.5 345.52 ,D,l2 (3.81 eV) 345.35 ,D,i2 (4.02 eV) 4D7,, (3.63 eV) 341.2 molybdenum 379.8 'P,''(3:26 eV) tungsten 400.9 'P, (3.46 eV) manganese 403.1 6P,,2(3.08 eV) '
5D3(0.05 eV) 5D, (0.00 eV) 3D3(0.03 eV) 3D3(0.03 eV) 3D3(0.03 eV) 7 S , (0.00 eV) 7S, (0.00 eV) 4F,12(0.43 eV
4F312(0.22 eV ,FgI2(0.43 eV 4FOI,(0.00 eV 7S;((0.00 eV) 7S3(0.37 eV) 6 S 5 / 2(0.00 eV)
proportional to the atomic ratio. It is necessary to find a pair of emission lines so that their excited states may have almost the same energy levels in several iron-base alloys. Further, it is also significant to get rid of the influence of gas emission and overlaps among the analytical lines. In Fe-Ni, Fe-Cr, Fe-Co, Fe-Mo, Fe-W, and Fe-Mn systems, Fe I 344.1 nm is the most suitable resonance line for the above assumptions in the wavelength range of 300-400 nm. This iron line, whose intensity is the most intense in the low wattage glow discharge region (up to about 20 W), consists of Fe I 344.099 nm and Fe I 344.061 nm lines (12). When the Fe 1344.1 nm line is chosen as the internal standard line, the emission lines for the others can be decided as shown in Table
11. It is desirable to select neighboring lines as well as possible, so that the variation of the spectrometer sensitivity depending on the wavelengths can be canceled. Though the positions of the selected lines for molybdenum, tungsten, and manganese are away from that of the Fe I 344.1 nm line, more adequate lines do not exist. These lines are employed only for the calibration curves in the later section. Electric power supplied to the glow lamp is employed to control the plasma and sputtering conditions. The peak height of each emission line is normalized in accordance with I,/& + Ib) (where I , is the peak intensity of emission line a and Ib is the peak intensity of the Fe 1344.1 nm line in most cases). Effect of Self-Absorption. In order to estimate the degree of self-absorption, we can examine the intensity ratio of two different emission lines of the same element. In Fe-Ni alloys, the normalized intensities for two different resonance lines (Fe I 344.1 nm/Fe I 374.5 nm for iron and Ni I 341.5 nm/Ni 1352.5 nm for nickel) are constant over the power range of 4-14 W. Similar phenomena are observed in the case of F e C o or Fe-Cr alloys. Therefore, in the low-wattage GDS, if these emission lines are employed (see Table 11))the influence of self-absorption to the measured intensity ratio can be neglected. The investigation of the intensity ratio provides the information on the sputtered atom compositions on the basis of eq 1. Dependence of Normalized Intensity upon Input Power. Figure 1 indicates the relation between the normalized nickel intensities (Ni I 341.5 nm and Ni I 352.5 nm) and the input power in Fe-49.9 atom % Ni. Their intensities show that ambiguous tendencies increase below 8.0 W. As shown in Figure 2, in Fe-19.1 atom % Co, the cobalt intensities, which are obtained from three different emission lines (Co I 340.5 nm, 341.2 nm, and 345.5 nm), slightly increase with
ANALYTICAL CHEMISTRY, VOL. 56, NO. 6, MAY 1984
910
49 9
at
"I
% NI
0.81
r
I
I
I
I
;
0.6
W I-
I
I
I
31.6 at 70Cr
1
o o o o
f0 . 7
J
.J 0.4
Fe Ni
Fe
344.1nrn
Cr 0 3 6 r . 3
0 3 4 . 5
0 352.5 nrn
L
4
8
12
Watt
OS0.5nrn
L
4
8
POWER
"I
19.1 at%Co
nm) as a function of the input power in Fe-31.6 atom % Cr.
*I
i
N
N
a
-I
3
B0
Fe
344 l n m
I
:..
Fe
8
12
I
1
- 19.7Ni -22.0019CCt
00 0 00
O O o o O o 0
00 8 O
0 0 0 0
80;
8 e 0
8;
0
0
a 0 0.3z
0 Nil 341.5nm 0 C r I 359.3nm
COO340 5 0341 2 0 345.5 nm
4
I
I
:**oo
n w
0
W
I
: 0.5
0.3
0.1.
wan
Flgure 3. Plot of the normalized Cr intensity (Cr I 359.3 and 360.5
I
z
'2
POWER
Figure 1. Plot of the normalized Ni intensity (Ni I 341.5 and 352.5 nm) as a function of the input power in Fe-49.9 atom % Ni.
P
344.1 nm
4
8
12
I
watt
watt
POWER Figure 2. Plot of the normalized Co Intensity (Co I 340.5, 341.2, and 345.5 nm) as a function of the input power in Fe-19.1 atom % Co.
an increase in the supplied power. However, their changes are very small in both cases. On the other hand, it is clearly recognized that the normalized chromium intensity decreases in proportion to the power up to 8.0 W as shown in Figure 3. If these results derive from the sputtering characteristics, they should be qualitatively explained by the sputtering yield (the number of sputtered atoms per a incident particle). The observed and theoretical sputtering yields of pure elements or several alloys have been reported (14, 15). According to the semitheoretical calculations of Andersen et al. (16),the sputtering yield for pure elements is 3.4 for iron, 3.5 for nickel, and 3.5 for chromium at 2.0 keV argon, respectively. Furthermore, the experimental yield obtained by Wehner et al. (17) is 1.26 for iron, 1.52 for nickel, 1.36 for cobalt, and 1.30 for chromium at 600 eV Ar+, respectively. As a result, it is concluded that the sputtering yields are almost
POWER Flgure 4. Relation between the input power and the normalized intensity for nlckel (Ni I 341.5 nm) or chromium (Cr I 359.3 nm) in Fe-19.7 Ni-22.0 atom % Cr ternary alloy.
the same among these four elements, independent of the kinetic energy of primary ions. In Fe-Ni and Fe-Co systems, our sputtering yield results are in qualitatively agreement with those of earlier works, but for Fe-Cr alloys, our results disagree. However, it is expected that a very stable and firm oxide film (Cr203)is formed on the surface with the impurities (water and oxygen) contained in argon gas. Because it is difficult to destroy the oxide film with a decrease in the input power, the normalized chromium intensity increases; that is, the primary ions collide with not the alloy surfaces but the chromium-rich oxide surfaces. In fact, the peak height of iron emission lines drops much more abruptly compared to the intensity decrease in chromium emission lines below 8.0 W. Figure 4 shows the normalized intensity-power curves for Fe-19.7 Ni-22.0 atom % Cr ternary alloy. In contrast to the
ANALYTICAL CHEMISTRY, VOL. 56, NO. 6, MAY 1984
ported from conventional studies; that is, the surfaces of stainless steels consist of the chromium-rich protective oxide films (18). Therefore, we interpret the observed dependence of the chromium intensities on the input power as arising from the chromium oxide prominently formed in very low wattage glow discharge regions. Influence of Alloy Composition on Sputtering. The results of several different concentrations in Fe-Ni alloy are shown in Figure 5. No peculiar composition dependence of the normalized nickel intensity on the supplied power is found; therefore, the sputtering yield ratios of each element in Fe-Ni are constant through all the compositions. Though no experiments are carried out over all the concentration range, the particular behavior resulting from the alloy compositions does not appear up to 31.6 atom % Cr in Fe-Cr alloy and up to 20.0 atom 70 Co in Fe-Co alloy, respectively.
Table 111. Proportionality Factors for the Selected Emission Lines to the Iron Line of 344.1 nm emission line, nm
element nickel chromium cobalt molybdenum tungsten manganese
339.3 341.5 352.5 359.3 360.5 340.5 341.2 345.5 379.8 400.9 403.1
factor allowed contenta 0.735 1.88 2.63 2.12 1.78 0.778 1.07 1.64 2.63 1.68 3.72
911
0-80 atom % Ni
0-30 atom % Cr 0-20 atom % Co 0-5 atom % Mo 0-7 atom % W 0-10 atom % Mn
The concentration range in which the linearity of calibration curves is confirmed by our experiments.
Relation between Observed Intensity Ratio and Bulk Composition. The mean intensity ratios, which are calculated
increase in the nickel intensity, the chromium intensity clearly decreases with the supplied power. These results are sup-
from the average values of 10-20 points in the range of the
Table IV. Analytical Results of Several Iron-Base Ternary Alloys atomic ratioa sample
Ni/Fe
Cr/Fe
Co/Fe
Mo/Fe
W/Fe
FXS-424 0.337) (0.377) 0.328 i 0.011 0.376 i 0.017
FXS-468 1.667) (0.740) 1.607 I 0.068 0.666 i 0.019
Ni 341.5, Cr 360.5 nm Ni 362.5, Cr 359.3 nm
1.515 i. 0.072 0.710 i 0.025 (0.342) 0.345 i 0.020
Ni 339.3, Co 340.5 nm Co 345.5 nm
0.390 i 0.011 (0.363) (0.333) 0.352 f 0.021 0.338 I 0.015
FXS-437
0.390
FXS-425 (0.267) 0.265 i 0.010
i
Cr 360.5, Co 340.5 nm Co 345.5 nm
0.011
(0.025) 0.027 i 0.003
Ni 341.5, Mo 379.8 nm Ni 339.3 nm
0.261 i 0.012 FXS-4 33
(0.316) 0.347 f 0.017 0.377
i
(0.029) 0.033 i 0.004
Cr 360.5, Mo 379.8 nm Cr 345.5 nm
0.022
FXS-444
(0.259) (0.025) 0.254 I 0.015 0.027 i 0.002 0.251 i 0.010
FXS-430 (0.273) 0.318 i 0.008
(0.021) 0.018 i 0.001
0.294 f 0.010 FXS-438
FXS-414 (0.295) 0.283 f 0.011
(0.297) 0.277 f 0.015 0.279 i 0.024
analytical lines Ni 341.5, Cr 360.5 nm Ni 352.5, Cr 359.3 nm
0.323 i 0.009 0.393 f 0.019
FXS-429 (0.340) 0.331 i 0.013
Mn/Fe
(0.024) 0.023 i 0.002
Co 340.5, Mo 379.8 nm Co 345.5 nm
Ni 341.5, W 400.9 nm Ni 359.3 nm Cr 360.5, W 400.9 nm Cr 359.3 nm
(0.140) 0.153 + 0.009 N i 341.5, Mn 403.1 nm 0.291 I 0.012 Ni 352.5 nm FXS-415 (0.354) (0.160) 0.367 i 0.026 0.195 i 0.009 Cr 360.5, Mn 403.1 nm FXS-420 (0.243) (0.150) 0.235 I 0.021 0.187 f 0.007 Co 340.5, Mn 403.1 nm 0.277 i 0.022 Co 345.5 nm Certified atomic ratios are denoted in parentheses. Average and the standard deviation are based on 10-15 replicates.
912
ANALYTICAL CHEMISTRY, VOL. 56, NO. 6, MAY 1984
--~-_____--
-__
Table V. Analytical Results of Commercial Stainless Steels sample
Si/Fe
SUS 410L
(0.010)
Mn/Fe (0.010) 0.014
SUS 430
SUS 304 SUS 304 SUS 304 SUS 304L SUS 321
SUS 316
(0.009) (0.025) (0.019) (0.027) (0.027) (0.019) (0.014)
SUS 316
(0.018)
SUS 316L
(0.027)
SUS 31651
(0.028)
SUS 309s
(0.023)
SUS 3105
(0.025)
F
0.001
Ni/Fe
atomic ratioa Cr/Fe
(0.001) N.D.
(0.010)
(0.005)
0.015 I 0.002 (0.029) 0.031 F 0.001 (0.025) 0.026 F 0.003 (0.027) 0.027 t 0.002 (0.025) 0.026 t 0.002 (0.024) 0.024 'i 0.002 (0 022) 0.018 i 0.001 (0.029) 0.028 i 0.002 (0.027) 0.024 i 0.003 (0.025) 0.925 i. 0.001 (0.030) 0 . 0 3 6 ~0.003 (0.036) 0.040 i 0.002
N.D. (0.249) 0.242 f (0.127) 0.119 i (0.134) 0.125 i (0.156) 0.149 i (0.140) 0.133 t (0.161) 0.154 i (0.151) 0.138 i (0.222) 0.209 I (0.194) 0.176 i (0.236) 0.220 i (0.379) 0.354 i
0.012 0.008 0.005 0.007
0.008 0.007
0.008 0.007 0.009
0.011 0.015
-
-
Mo/Fe
Cu/Fe
(0.001) N.D. (0.001) N.D.
(0.163) 0.179 t 0.008 (0.230) 0.254 i 0.012 (0.342) 0.353 2 0.013 (0.304) 0.315 t 0.020 (0.285) 0.308 I0.017 (0.306) 0.319 I 0.019 (0.279) 0.307 F 0.017 (0.290) 0.279 i 0.016 (0.269) 0.283 i 0.016 (0.300) 0.319 I 0.019 (0.314) 0.339 i 0.017 (0.426) 0.467 t 0.029 (0.543) 0.609 i 0.032
(0.001)
N.D. (0.001) N.D.
(0.035)
(0.003)
N.D.
N.D.
(0.002)
(0.002)
N.D.
N.D.
(0.003)
(0.002)
N.D.
N.D.
(0.002)
(0.002)
N.D.
N.D.
(0.002)
(0,001)
N.D.
N.D.
(0.020) 0.024 F (0.023) 0.028 i (0.024) 0.031 t (0.024) 0.032 F (0.002)
(0.003) 0.002
N.D. (0.003) N.D.
0.004
N.D.
0.002
(0.017) 0.019 t 0.005 (0.002)
0.002
(0.004)
N.D.
N.D.
(0.002)
(0.002)
N.D.
N.D.
a Standard atomic ratios are denoted in parentheses. N.D., not detected. Analytical lines: Mn, 403.1 nm; Ni, 341.5 nm; Cr, 360.5 nm; Mo, 379.8 nm; Cu, 327.4 nm. Proportionality factor: 1.6 for copper 327.4 nm (calculated from the intensity ratio in Fe-1.0 atom % Cu alloy). Average and the standard deviation are based on 10-15 replicates.
supplied power from 10 to 15 W, are directly proportional to the bulk compositions for almost all pairs of emission lines. The proportionality factors are obtained from the slopes of these resulting straight calibration curves as arranged in Table
r
I
I
I
I
I
I
I
111. On the basis of these factors, it is possible to estimate the alloy concentration with the assumption that the calibration curves for binary alloys can be applied to the multicomponent iron-base alloy. Some iron-base ternary alloys and commercial stainless steels are quantitatively analyzed in the next section. Quantitative Analysis by the GDS. Twelve iron-base ternary standard samples are analyzed by the GDS. Table IV shows the atomic ratios of these alloys certified by the Iron and Steel Institute of Japan: In binary alloys, all the emission lines listed in Table I11 are employed; however, in ternary alloys, available lines are restricted due to the overlapping of the emission lines among alloyed elements. For example, it is impossible to select Ni 1341.5 nm, Ni 1352.5 nm, and Cr 1359.3 nm in the case of cobalt-containing alloys. With these interferences considered the analytical lines for each alloy are decided as shown in Table IV. Table IV also shows the observed atomic ratios and the standard deviations (standard error of the mean) computed from the proportionality factors for each emission line and from the average intensity ratios of 10-15 measurements in the power range 10-15 W. The average error of 7.1% is calculated from all the results and the related certified values in Table IV. Finally, this method is applied to the investigation of some major elements in commercial stainless steels. It is possible to estimate simultaneously the content of the major elements containing more than 1.0 atom % in a sample except for silicon (no suitable emission line exists for Si). Analytical results are summarized with the standard values in Table V. This method cannot be applied to the analysis of minor elements and impurities in a sample because the emission intensity is relatively weak. However, as the linearity of calibration curves is maintained over the wide concentration
0.71
o.2t
I
.L, >
4
8
'2
Watt
POWER Flgure 5. Influence of the alloy concentration on the normalized Ni intensity in Fe-Ni over the power range from 4.0 to 15.0 W.
range, the quantification by the low-power GDS is suited to the study of major elements. Furthermore, this method has the following merits: (a) constant experimental conditions are easily kept for a long time because accumulated deposit around the anDde is less compared to the high-power glow discharge; (b) troublesome sampling procedures and elemental preseparations are not required; (c) the calibration curves for binary alloys examine the multielement samples within an error of ca. 20%. On the other hand, when the more accurate analytical results are needed, a more sensitive or complicated measuring method should be required.
Anal. Chem. 1984, 56, 913-918
Registry No. Ni, 7440-02-0;Cr, 7440-47-3; Co, 7440-48-4;Mo, 7439-98-7; W, 7440-33-7; Mn, 7439-96-5; Si, 7440-21-3; Cu, 7440-50-8;F e N i alloy, 11148-11-1;Fe-Cr alloy, 11101-78-3;Fe-Co alloy, 12638-90-3;chromium-nickel-iron-base alloy, 12619-49-7; cobalt-nickel-iron-base alloy, 39437-22-4; chromium-cobaltiron-base alloy, 39437-18-8;chromium-molybdenum-iron-base alloy, 62963-49-9;molybdenum-nickel-iron-base alloy, 12727-80-9; cobalt-molybdenum-iron-base alloy, 39446-85-0; nickel-tungsten-iron-base alloy, 39437-54-2; chromium-tungsten-iron-base alloy, 51614-33-6; chromium-manganese-iron-base alloy, 1264866-7; cobalt-manganese-iron-base alloy, 39437-21-3; manganese-nickel-iron-base alloy, 11135-35-6. LITERATURE CITED Grimm, W. Naturwissenschaften 1967, 54, 588. Grlmm, W. Spectrocbim. Acta, Part B 1988, 2 3 8 , 443. Boumans, P. W. J. M. Anal. Chem. 1972, 4 4 , 1219. Hirokawa, K. Bunko Kenky#l872, 22, 317. West, C. D.; Human, H. G. Spectrochim. Acta, Part B 1976, 318, 81. Berneron, R.; Charbonnler, J. C. S I A , Surf. Interface Anal. 1981, 3 , 134.
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(7) Yamada, T.; Kashima, J.; Naganuma, K. Anal. Cbim. Acta 1981, 124, 275. (8) Ohashi, Y.; Yamamoto, Y.; Tsunoyama, K.; Kishidaka, H. SIA , Surf. Interface Anal.,#l979, 1 , 53. (9) von Engei, A. Ionized Gases"; Oxford University Press: Oxford, 1965. (10) Waitievertch, M. E.; Hurwitz, J. K. Appl. Spectrosc. 1978, 30, 510. (11) Wagatsuma, K.; Hirokawa, K. Anal. Cbem. 1984, 5 6 , 412. (12) Zaidel, A. N.; Prokof'ev, V. K.; Raiskii, S. M. "Spektraitabellen"; VEB Verlag Technik: Berlin, 1961. (13) Moore, C. E. "Atomic Energy Levels"; Natl. Bur. Stand. ( U . S . ) ,Circ. 1849, No. 467. (14) Behrisch, R., Ed. "Sputtering by Particle Bombardment I"; SpringerVerlag: Berlin, 1981; Chapter 4. (15) Betz, G. Surf. Sci. 1980, 92, 283. (16) Laeareid. N.: Wehner. G. K. J. A m / . Phys. 1961, 32, 365. i17) A n d k e n , H. H.; Bay, H. L. ffadiit. Eff. 1972, 13, 67. (18) Kubaschewski, 0.; Hopkins, B. E. "Oxidation of Metals and Alloys"; Butterworth: London, 1962; Chapter 4.
RECEIVED for review November 28,1983. Accepted February 26, 1984' We are grateful to Nissan Science Fundation for the financial support of our work.
Total Solid-Surface Room-Temperature Luminescence for Analysis of Mixtures V. P. Senthilnathan and R. J. Hurtubise*
Department of Chemistry, The University of Wyoming, Laramie, Wyoming 82071
Nltrogen heterocycles and one poiycycllc aromatic hydrocarbon were combined to form varlous blnary and ternary mixtures of the compounds. The components were determined at the nanogram level by a comblnation of room-temperature fluorescence and room-temperature phosphorescence with selective excitation and emission. Wlth fiuorescence and phosphorescence calibration curves, It was posslble to determine ail components in a glven mlxture without Isolation of the components. For the mixtures Investigated, the smallest amount of materlal that could be determined accurately was about 2.5 ng.
Solid-surface luminescence analysis is generally considered to involve the use of either fluorescence or phosphorescence from organic compounds adsorbed on surfaces for organic trace analysis. Hurtubise (I) has given a detailed survey of theory, instrumentation, and applications in solid-surface luminescence analysis. Parker et al. have recently reviewed the analytical considerations of room-temperature phosphorescence (RTP) (2) and have also surveyed the aspects dealing with the physical nature of RTP (3). Fluorodensitometry has long been used in organic trace analysis. One particularly important use of this technique is in the determination of mycotoxins (4).In the 1960s, Sawicki and co-workers pioneered in the development and application of room-temperature solid-surface fluorescence analysis and low-temperature solid surface phosphorescence analysis in air pollution research. Sawicki (5) and Sawicki and Sawicki (6) have reviewed several aspects of luminescence analysis in air pollution research. Vo-Dinh and co-workers (7-10)have successfully applied synchronous fluorescence spectroscopy and the RTP technique to the analysis of polycyclic aromatic hydrocarbons in coal liquid samples or samples originating from coal con0003-2700/84/0356-09 13$01.50/0
version processes. In the synchronous fluorescence work, solutions were used while with the RTP work filter paper was used to induce R T P signals. Ford and Hurtubise (1I) employed both solid-surface fluorescence and phosphorescence at room temperature to characterize 5,6-benzoquinoline and phenanthridine in shale oil. It appears that there have been no previous reports of the combined use of solid-surface fluorescence and phosphorescence at room temperature for quantitative analysis. This is not surprising because RTP analysis is a recent development in organic trace analysis. By use of both the fluorescence and phosphorescence signals at room temperature from various compounds in a mixture adsorbed on a surface, certain distinct analytical advantages are obtained. In this work, both luminescence phenomena were used for the quantitative analysis of mixtures of compounds a t the nanogram level without prior separation. This new approach is called total solid-surface luminescence analysis (TSSLA).
EXPERIMENTAL SECTION Apparatus. All RTP intensity data were obtained with a Schoeffel SD 3000 spectrodensitometer equipped with a SDC 300 density computer (Schoeffel Instruments, Westwood, NJ) and a phosphoroscope assembly. Details of the instrumental setup were discussed previously (12). Relative RTP signals were measured with the spectrodensitometer with the inlet and exit slits set at 2 mm and 3 mm, respectively. A 200-W Xe-Hg lamp (Conrad Hanovia Inc., Newark, NJ) and R928 photomultiplier tube (Hamamatsu Corp., Middlesex, NJ) were employed in the spectrodensitometer. Room-temperaturefluorescence (RTF) data were obtained without the phosphoroscope assembly. Fluorescence and phosphorescence excitation and emission spectra were obtained with a Farrand MK-2 spectrofluorimeter. The Farrand MK-2 phosphorescence rotary chopper was activated for the phosphorescence spectra. Metal slits giving a bandwidth of 10 nm were used at the entrance and exit positions of both the excitation and emission monochromators for RTP measurements, 0 1984 American Chemical Society
