Modulated Glow Discharge Source With Supplementary Microwave Excitation

Abstract

Spectral interferences occurring in a microwave-boosted glow discharge source due to emission lines of the carrier gas and to band systems of molecular species were investigated. A method is described which greatly reduces such interferences. It is shown that analytical lines are strongly dependent on the current in the dc discharge whereas Ar I lines are scarcely influenced and OH bands are influenced to only a small extent. By modulating the dc current with the microwave discharge running continuously and using a lock-in amplifier, selective amplification of analyte atomic lines is achieved. In this way, spectral interferences by Ar I lines on Fe I lines and interferences by lines in OH bands on the Bi I 306.771 nm and Al I 308.216 and 309.271 nm analytical lines, which occur even when using a high resolution monochromator, are greatly reduced.

References

1. W. Grimm, Naturwissenschaften, 1967, 54, 588.
2. W. Grimm, Spectrochim. Acta, Part B, 1968, 23, 443.
3. F. Leis and E. B. M. Steers, Spectrochim. Acta, Part B, 1994, 49, 289.
4. M. Dogan and A. Ülgen, Fresenius' J. Anal. Chem., 1996, 355, 651.
5. K. Wagatsuma and K. Hirokawa, Anal. Sci., 1991, 7, 289.
6. A. Ülgen, M. Dogan, A. Gökmen and S. Yalcin, Spectrochim. Acta, Part B, 1993, 48, 65.
7. K. Wagatsuma and K. Hirokawa, Anal. Chem., 1984, 56, 2732.
8. K. Wagatsuma and K. Hirokawa, Spectrochim. Acta, Part B, 1988, 43, 831.
9. M. Outred, M. H. Rümmeli and E. B. M. Steers, J. Anal. At. Spectrom., 1994, 9, 381.
10. F. Leis, J. A. C. Broekaert and K. Laqua, Spectrochim. Acta, Part B, 1987, 42, 1169.
11. R. C. M. Learner, A. P. Thorne, I. Wynne-Jones, J. W. Brault and M. C. Abrams, J. Opt. Soc. Am., A: Opt. Image Sci., 1995, A12, 2165 and references cited therein.
12. M. Dogan, K. Laqua and H. Massmann, Spectrochim. Acta, Part B, 1972, 27, 65.