Anal. Chem. 1991, 63, 2137-2140 Control Board, Los Angeles, CA; Southern California Coastal Water Research Probct: Long Beach, CA, Sept 1990; 34 pp. (22) Anderson, J. W.; Gossett, R. W. Polynuclear Aromatlc Hydrocarbon Contamhation in Sediments from Coastal Waters of southern California. Final Report to the California State Water Resources Control Board Southern California Coastal Water Research Project: Long Beach, CA, 1987; 51 pp. (23) BallschmRer, K.; Zeil, M. Fresenius' Z . Anel. Chem. 1980, 302,20. (24) Hu, T.C. L.; Gossett, R.; Young, D. Mass spectromtty confirmation of PCB and DDT analyses of fish. In: BiennislReport 1979-80: South-
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RECEIVED for review February 15,1991. Accepted June 28, lggl*This work was funded in part by the Regional Water Quality Control Board.
Determination of Rare-Earth Elements by Inductively Coupled Plasma Mass Spectrometry with Ion Chromatography K. Kawabata,* Y. Kishi, 0. Kawaguchi, Y. Watanabe, and Y. Inoue Analytical Instruments Division, Yokogawa Electric Corporation, Musashino-shi, Tokyo 180, Japan
Inductlvely coupled plasma mass spectrometry (ICPMS) has been used for analysis of trace rare-earth elements as Impurities that exlst In other rare-earth material. ICPMS attains the pg-mL-l level detection In sdutlon for ail of the rare-earth elements by means of a conventional introductlon system. On the other hand, an Interference problem due to polyatomic Ions Is well-known and is especially critical for determlnatlon of the rare-earth elements. I n order to solve thls problem, the ion chromatographlc analyzer was comblned with ICPMS. After separation from a maln materlal by Ion chromatography (IC), trace rare-earth elements were directly Introduced to ICPMS and analyzed. The detection limlts for 14 rare-earth elements were from 1 to 5 pg-mL-l in solution and ngeg-' in solid. The h e a r range was lo6, from 10 pg0mL-l to 10 pg. mL-l, and the repeatablilty was better than f l % of the relatlve standard deviatlon (RSD) for Lu.
INTRODUCTION Since the rare-earth elements (REE) were used in the optical glass industry, their application in other fields has been rapidly expanded. A presence of REE in high-purity metals, semiconductors, and glasses plays an important role in influencing electrical, magnetic, and optical properties. As the demand for purity of REE is increasing, development of new analytical procedures is expected, which is not only rapid and accurate but also offers high sensitivity. Since a paper on ICPMS was published by Houk et al. in 1980 (I), its analytical capabilities have been reported by many researchers. ICPMS has several attractive features compared with other analytical techniques including spectra are simple to interpret and mainly free from interelement interferences, isotopic information is inherent, multielemental capability allows higher sample throughput, detection limits are superior to most conventional techniques with wide dynamic range, and most of the elements in the periodic table can be detected. On the other hand, several problems were indicated by researchers (2-5). A principal problem is interferences due to polyatomic ions and isobars. For REE this problem can be more serious because lighter REE form their own polyatomic ions that interfere in the determination of heavier REE; e.g. GdO+ and GdOH+ overlap all the isotopes of Yb and Lu, and LaH+ hinders the most abundant and free isotope of Ce. 0003-2700/91/0363-2137$02.50/0
Table I. ICPMS Operating Conditions ICPMS instrument
Yokogawa PMS 200
forward power reflected power coolant gas flow auxiliary gas flow carrier gas flow distance from load coil to sampling orifice
1.4 kW
