Evaluation of inductively coupled plasma-ion trap mass spectrometry for lead isotopic measurements

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1 BUNSEKI KAGAKU Vol. 53, No. 6, pp. 527 _ The Japan Society for Analytical Chemistry 1 1 R 1 2 Evaluation of inductively coupled plasma-ion trap mass spectrometry for lead isotopic measurements Yasuhiro NISHIMURA 1, Masaki OHATA 1, Naoki FURUTA 1 and Takayuki NABESHIMA 2 1 Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, , Kasuga, Bunkyo-ku, Tokyo Hitati High-Technologies Corporation, , Nishishinbashi, Minato-ku, Tokyo (Received 14 January 2004, Accepted 10 March 2004) In this paper, an ICP coupled with a three dimensional quadrupole mass spectrometer (ICP-3DQMS) was evaluated for lead isotopic measurements. The 3DQMS is a type of an ion trap mass spectrometer. These days, ICP coupled with a quadrupole mass spectrometer (ICP-QMS) is widely used for its advantages of high sensitivities and capability of isotopic measurements. However, the obtained precision ( RSD) of the isotopic measurements is limited to about 0.3, because several isotopes are detected sequentially. On the other hand, because 3DQMS can trap several isotopes simultaneously, a precision of less than 0.1 (ca ) could be achieved for 207 Pb/ Pb and 208 Pb/ Pb in this study. One drawback of 3DQMS is that there is a limitation on the number of total ions, that can be trapped. It was found that the value of [trapping time (ms) concentration (ng/ml)] influences the accuracy and precision of isotopic measurements. Keywords : inductively coupled plasma ; ion trap ; lead isotopic measurements ; ICP-MS ; ICP-3DQMS Pb Pb 207 Pb 208 Pb 204 Pb Pb 207 Pb 238 U 235 U 208 Pb 232 Th U Th : : TIMS 1)2) TIMS TIMS 1 ICP- QMS TIMS ICP-QMS TIMS TIMS ICP-QMS

2 528 BUNSEKI KAGAKU Vol Fig. 1 Schematic diagram of ICP-3DQMS Fig. 2 Schematic diagram of 3DQMS ) ICP 4) 5) ICP-QMS ICP S/N 2 6) 8) 3DQMS P-5000 ICP- 3DQMS ICP-3DQMS 9) 13) ICP-3DQMS DQMS P-5000 Hitachi High-Technologies Co. 3DQMS Fig. 1 3DQMS 3 ICP DQMS Fig. 2 3DQMS 3DQMS 2 1 3DQMS He

3 : 529 Table 1 Typical operating conditions of ICP RF power 1100 W Plasma gas flow rate 14 l min 1 Carrier gas flow rate 1.3 l min 1 Auxiliary gas flow rate 1.0 l min 1 Up-take rate 0.4 ml min Pb NIST SRM M HNO ng/ ml 1 µg/ml 2 3 ICP Table 1 m/z 210 3DQMS Pb 3DQMS trapping time ICP-3DQMS 3DQMS CID collision induced dissociation m/z Pb Pb/ Pb 208 Pb/ Pb Pb 3DQMS Pb 3DQMS Fig ng/ml Pb 208 Pb 100 ms Fig. 3 Pb signal intensities observed by using a 100 ng/ml Pb standard solution as a function of trapping time of ICP-3DQMS The number of accumulation was 50 times. : Pb ; : 207 Pb ; : 208 Pb Fig. 4 Pb isotope ratios observed by using a 100 ng/ml Pb standard solution as a function of trapping time of ICP-3DQMS The number of accumulation was 50 times. : 207 Pb/ Pb ; : 208 Pb/ Pb Pb 207 Pb 300 ms 3DQMS 208 Pb Pb 207 Pb ms Pb 207 Pb 300 ms Fig Pb/ Pb 100 ms 208 Pb 100 ms 207 Pb/ Pb 750 ms Fig. 3 Pb 207 Pb 300 ms 300 ms Pb

4 530 BUNSEKI KAGAKU Vol Fig. 5 ICP-3DQMS mass spectra for Pb observed by using a 100 ng/ml Pb standard solution for different trapping times The number of accumulation was 50 times. : trapping time 100 ms ; : trapping time 1000 ms Fig. 6 Pb isotope ratios observed for different concentrations as a function of [trapping time (ms) concentration (ng/ml)] The number of accumulation was 50 times. : 207 Pb/ Pb 10 ng/ml ; : 207 Pb/ Pb 50 ng/ml ; : 207 Pb/ Pb 100 ng/ml ; : 208 Pb/ Pb 10 ng/ml ; : 208 Pb/ Pb 50 ng/ml ; : 208 Pb/ Pb 100 ng/ml 207 Pb 207 Pb/ Pb NIST SRM Pb/ Pb DQMS Pb 207 Pb 208 Pb m/z m/z 3 m/z 207 Pb Pb 208 Pb Pb 208 Pb 207 Pb 207 Pb 207 Pb/ Pb NIST SRM ms Pb 208 Pb 100 ng/ml Pb 207 Pb 300 ng/ml 208 Pb/ Pb 100 ng/ml 207 Pb/ Pb 750 ng/ml Pb 3DQMS Fig ng/ml Pb 100 ms 1000 ms 100 ms 1000 ms 1000 ms 3DQMS 100 ms Pb 208 Pb Pb 3DQMS Pb 207 Pb 208 Pb Pb 208 Pb 3DQMS 208 Pb 3DQMS 0.25 m/z Pb 3DQMS ms ng/ml Fig ng/ml Pb

5 : 531 Fig. 7 RSD of Pb isotope ratio measurements obtained by ICP-3DQMS as a function of [trapping time (ms) concentration (ng/ml)] The number of accumulation was 100 times. : 207 Pb/ Pb ; : 208 Pb/ Pb 3DQMS ICP- 3DQMS 208 Pb/ Pb Pb/ Pb Fig Fig ng/ml 30 ms Fig. 8 RSD of Pb isotope ratio measurements obtained using a 30 ms trapping time and a 100 ng/ml Pb standard solution as a function of number of accumulation Results were compared to theoretical values which were calculated by assuming random statistics. : 207 Pb/ Pb measurement value ; : 207 Pb/ Pb theoretical value ; : 208 Pb/ Pb measurement value ; : 208 Pb/ Pb theoretical value 3DQMS Table Pb/ Pb 208 Pb/ Pb 0.08 ICP-QMS ICP-3DQMS CID

6 532 BUNSEKI KAGAKU Vol Table 2 Measurements Signal intensities of Pb isotopes (counts) and Pb isotope ratios obtained by ICP-3DQMS using a 100 ng/ml Pb standard solution (NIST SRM 981) Pb 207 Pb 208 Pb 207 Pb/ Pb 208 Pb/ Pb # # # # # Mean SD RSD NIST certified value Pb ng/ml 30 ms ),, :, 1479 (1982). 2) Y. Hirao, H. Mabuchi, E. Fukuda, H. Tanaka, T. Imamura, H. Todoroki, K. Kimura, E. Matsumoto : Geochemical J., 20, 1 (1986). 3) C. R. Quetel, B. Thomas, O. F. X. Donard, F. E. Grousset : Spectrochim. Acta, Part B, 52, 177 (1997). 4) N. Furuta : J. Anal. At. Spectrom., 6, 199 (1991). 5) D. J. Douglas : Fundamental Aspects of Inductively Coupled Plasma-Mass Spectrometry, in Inductively Coupled Plasmas in Analytical Atomic Apectrometry, 2nd ed., Edited by A. Montaser, D. W. Golightly, p. 613 (1992), (VCH, New York). 6) K. G. Heumann, S. M. Gallus, G. Radlinger, J. Vogl : J. Anal. At. Apectrom., 13, 1001 (1998). 7) A. J. Walder, N. Furuta : Anal. Sci., 9, 675 (1993). 8) A. R. Warren, L. A. Allen, H-M. Pang, R. S. Houk, M. Janghorbani : Appl. Spectrosc., 48, 1360 (1994). 9) D. W. Koppenaal, C. J. Barinaga, M. R. Smith : J. Anal. Atom. Spectrom., 9, 1053 (1994). 10) G. C. Eiden, C. J. Barinaga, D. W. Koppenaal : J. Am. Soc. Mass Spectrom., 7, 1161 (1996). 11) G. C. Eiden, C. J. Barinaga, D. W. Koppenaal : J. Anal. Atom. Spectrom., 11, 317 (1996). 12) C. J. Barinaga, D. W. Koppenaal : Rapid Comm. Mass Spctrom., 8, 71 (1994). 13) N. Furuta, A. Takeda, J. Zheng, T. Nabeshima : Evaluation of Inductively Coupled Plasma-Ion Trap Mass Spectrometry, in Plasma Source Mass Spectrometry, Edited by G. Holland, S. D. Tanner, p. 90 (2001), (Royal Society of Chemistry). 3DQMSICP -3DQMS QMS 0.3 ICP ICP-3DQMS DQMS