Anal. Chem. 1983, 55, 1513-1516
1513
thetic Ocean mission Spectrometry
Determination of Trace Metals in Inductively Coupled Plasma with Electrothermal Carbon Cup Kin C. Ng and Joseph A. Caruso" Department of
Ch@mistry,University of Cincinnati,
Cincinnati, Ohio 4522 I
The Capability tor direct quantiflcatlon of trace elements In Table I. Compromise Operating Conditions high salt content water samples (as represented by the syncompromise thetic ocean water in this study) was explored. The ~ e t ~ ~ d condition parameter consists of drying and vaporlrlng samples electrothermally, plasma followed by plasma excitation of the vapor. No ashing step generator forward power 1000 was necessary, thus tho potential loss of ~~~~~~s In this step 0.999. Analyte concentrations >10 pprn were not investigated. Detection limits for the analytes in the 99% SW are defined as the net analyte emission intensities in 99% SW equivalent to 2 times the standard deviation of background emission intensity. For As, the detection limit is the lowest quantifiable level (0.62 mm on the tracing, expressed as intensity (14)). The detection limits are in the parts-per-billion levels with absolute detection limits in the subnanogram and picogram levels (Table III). To evaluate the accuracy of the system for the quantification of trace elements in SW, 0.97 ppm each of the elements was spiked in 97% SW and the recovery was performed by the method of standard additions. The general procedure and the signal response are illustrated in Figure 4 for Cd. The results of the recovery study are shown in Table IV. Acceptable recoveries are obtained in all cases. It should be noted that the recovery experiments (Table IV) were performed on different days and occasionally with different cups. Therefore,
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ANALYTICAL CHEMISTRY, VOL. 55, NO. 9, AUQUST 1983
precision, linearity, accuracy, and detection limits for the 5 fiL volume. The capability of the present system to handle high salt content solution can thus minimize or eliminate the potential contamination due to the dilution of samples. The operation of the system does not demand careful optimization. The severe matrix effect, however, requires that the method of standard additions or matrix matching with background correction be utilized. This technique should find applications in the direct analysis of many environmental, biolagical, and clinical samples where only small amounts of samples are available and high detectability is required. Registry No. As, 7440-38-2;Au, 7440-57-5;Cd, 7440-43-9;Li, 7439-93-2; Sn, 7440-31-5; Zn, 7440-66-6; water, 7732-18-5.
LITERATURE CITED (1) (2) (3) (4) (5)
1
a
1
2
3
C O N C E N T R A T I O N ADDED
(PPM)
Flgure 4. Recovery study of elements in synthetlc ocean water by using standard additions and Its emission response Illustrated by the cadmium (0.97 ppm, spiked concentration) in 97 % synthetic ocean water. -
Table IV. Spiked Recoveries Using Standard Additions of Six Trace Metals in 97%Synthetic Ocean Water spiked av concn concn, found, % recovery metal PPm PPm As a Au Cd: Li Sna Znb
0.97 0.97 0.97 0.97 0.97 0.97
0.93 0.87 0.90 0.97 1.04 0.99
96 i 4 89 i 3 92 + 4 100 10 107 i 4 102 * 4
*
Tantalum carbide pyrocoated carbon cup employed. Pyrocoated carbon cup employed.
a
the range of recovery values may represent uncertainties in reinitializating the system, in addition to the individual element response. This system has shown no memory in the consecutive determinations of high salt samples, while giving good signal
(6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19)
Fassei, V. A. Science 1978, 202, 183. Greenfield, S. Analyst (London) 1980, 705, 1032. Barnes, R. M. CRC Crit. Rev. Anal. Chem. 1978, 7 , 203. Meinhard, J. E. ICP I n f . News/. 1978, 2 , 163. Knlseley, R. N.; Amsnson, H.; Butler, C. C.; Fassel, V. A. Appl. Spectrosc. 1974, 2 8 , 285. Greenfleld, S.; McGeachln, H. McD.; Smith, P. B. Anal. Chim. Acta 1978,. 84,. 67. Gunn, A. M.; Millard, D. L.; Klrkbrlght, G. F. Analyst (London) 1978, 103, 1068. Kirkbright, G. F.; Snook, R. D. Anal. Chem. 1979, 57, 1938. Millard: D. L.; Shan, H. C.; Kirkbright, G. F. Analyst (London) 1980, 705, 502. Rlca, C. C.; Klrkbright, G. F.; Snook, R. D. At. Specrrosc. 1981, 2 , 172. Cope, M. J.; Kirkbrlght, Q. F.; Burr, P. M. Analyst(London) 1982, 707, 61 1. Azlz, A.; Broekaert, J. A. C.; Lels, F. Spectrochlm. Acta, Part6 1982, 376, 369. Crabi, G.; Cavalll, P.; Achllll, M.; Rossi, G.; Omenetto, N. At. Spectrosc 1982, 3 , 8 1. Ng, K. C.; Caruso, J. A. Anal. Chim. Acta 1982, 743, 209. Ng, K. C.; Caruso, J. A. Analyst (London), 1983, 108, 476. Huffman, H. L.; Caruso, J. A. Talanta 1975, 2 2 , 871. Issaq, H. J.; Morgenthaier, L. P. Anal. Chem. 1975, 4 7 , 1748. Blades, M. W.;Horilck, G. Spectrochlm. Acta, Part6 1981, 368, 881. Nygaard, D. D. Anal. Chem. 1979, 57, 881.
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RECEIVED for review December 27,1982. Accepted April 18, 1983. The authors are grateful for NIOSH support in the form of Grant No. OH 00739.
