Improved Signal-to-noise Ratio in Glow Discharge Ion Trap Mass Spectrometryvia Pulsed Discharge Operation

Abstract

An improvement in the S/N ratio is reported for the analysis of trace elements in brass by glow discharge ion trap mass spectrometry. This was achieved by synchronizing the pulsed discharge voltage with the ion injection and acquisition events; ‘on’ during ion injection and ‘off’ during data acquisition. Two modes of operation were evaluated: (1) a high duty cycle pulse, which allowed a continuous injection over the duration of the pulse; and (2) a low duty cycle pulse with multiple data gates, which allowed gated injections of ions at selected regions of the pulse profile. The latter afforded a means of selective ion injection since discharge and residual gas species are formed at different times in the pulse event than analyte ions. Improvements in S/N ratios greater than 40-fold were observed, primarily due to a reduction in background and background noise after the discharge was extinguished. Evidence is presented which suggests that electrons emanating from the ion source are the precursors of most of the noise. Detection limits for various elements were 0.2–0.5 ppm.

References

1. N. A. Yates, M. M. Booth, J. L. Stephenson, Jr. and R. A. Yost, in Practical Aspects of Ion Trap Mass Spectrometry, Vol. 3, Chemical, Environmental, and Biomedical Applications, ed. March, R. E., and Todd, J. F. J., CRC Press, New York, 1995, ch. 4.
2. B. L. Kleintop, D. M. Eades, J. A. Jones and R. A. Yost, in Practical Aspects of Ion Trap Mass Spectrometry, Vol. 3, Chemical, Environmental, and Biomedical Applications, ed. March, R. E., and Todd, J. F. J., CRC Press, New York, 1995, ch. 5.
3. J. N. Louris, J. W. Amy, T. Y. Ridley and R. G. Cooks, Int. J. Mass Spectrom. Ion Processes, 1989, 88, 97.
4. C. G. Gill, B. Daigle and M. W. Blades, Spectrochim. Acta, Part B, 1991, 46, 1227.
5. C. G. Gill and M. W. Blades, J. Anal. At. Spectrom., 1993, 8, 261.
6. M. L. Alexander, P. H. Hemberger, M. E. Cisper and N. S. Nogar, Anal. Chem., 1993, 65, 1609.
7. A. W. Garrett, P. H. Hemberger and N. S. Nogar, Spectrochim. Acta, Part B, 1995, 50, 1889.
8. S. A. McLuckey, G. L. Glish, D. C. Duckworth and R. K. Marcus, Anal. Chem., 1992, 64, 1606.
9. D. C. Duckworth, C. M. Barshick, D. H. Smith and S. A. McLuckey, Anal. Chem., 1994, 66, 92.
10. A. D. Appelhans, G. S. Groenewold, J. C. Ingram, J. E. Delmore and D. A. Dahl, Secondary Ion Mass Spectrometry, SIMS X, Wiley, New York, 1996.
11. C. J. Barinaga and D. W. Koppenaal, Rapid Commun. Mass Spectrom., 1994, 8, 71.
12. D. W. Koppenaal, C. J. Barinaga and M. R. Smith, J. Anal. At. Spectrom., 1994, 9, 1053.
13. C. I. Frum, Presented at the 44th ASMS Conference on Mass Spectrometry and Allied Topics, Portland, OR, May 12–16, 1996.
14. J. A. Klingler, P. J. Savickas and W. W. Harrison, J. Am. Soc. Mass Spectrom., 1990, 1, 138.
15. J. A. Klingler, C. M. Barshick and W. W. Harrison, Anal. Chem., 1991, 63, 2571.
16. F. L. King and C. Pan, Anal. Chem., 1993, 65, 735.
17. C. Pan and F. L. King, J. Am. Soc. Mass Spectrom., 1993, 4, 727.
18. C. Pan and F. L. King, Anal. Chem., 1993, 65, 3187.
19. R. E. Steiner, C. L. Lewis and F. L. King, Proceedings of the 43rd ASMS Conference on Mass Spectrometry and Allied Topics, Atlanta, GA, May 21–26, 1995, p. 42.
20. D. C. Duckworth and R. K. Marcus, J. Anal. At. Spectrom., 1992, 7, 711.
21. S. A. McLuckey, G. L. Glish and K. G. Asano, Anal. Chim. Acta, 1989, 225, 25.
22. R. Hergerberg, M. T. Elford and H. R. Skullerud, J. Phys. B: At. Mol. Phys., 1982, 15, 797.
23. H. Helm, J. Phys. B: At. Mol. Phys., 1977, 10, 3683.
24. S. A. McLuckey, D. E. Goeringer and G. L. Glish, J. Am. Soc. Mass Spectrom., 1991, 2, 11.
25. R. K. Julian, K. A. Cox and R. G. Cooks, Anal. Chem., 1993, 65, 1827.
26. D. E. Goeringer, K. G. Asano, S. A. McLuckey, D. Hoekman and S. W. Stiller, Anal. Chem., 1994, 66, 313.
27. G. C. Eiden, C. J. Barinaga and D. W. Koppenaal, J. Anal. At. Spectrom., 1996, 11, 317.