Determination of platinum, rhodium and palladium in exhaust fumes

Abstract

With the introduction of catalytic converters for reducing emissions of CO, NO_x and HC, a higher concentration of Pt, Pd and Rh is being observed in environmental samples. These platinum group elements (PGE) are the main active components of catalytic converters and they are mainly released as a result of surface abrasion of the catalyst during car operation. The present work reports the procedure employed for sampling, mineralization and determination of PGE by quadrupole ICP-MS in three different types of catalysts. Whole raw exhaust fumes were collected directly from the end of the exhaust pipe following the 91441 extra urban drive cycle (EUDC) using a newly developed sampling device. The sampling procedure allows the further differentiation between a soluble and particulate (insoluble) sample fraction. The release of pollutants such as Hf, Cu, Y, Rb, Sr and Pb present in the catalyst washcoat or in the fuel was also monitored since these elements cause spectral interferences in the determination of PGE. These spectral interferences, ¹⁷⁹Hf¹⁶O⁺ on ¹⁹⁵Pt, ⁴⁰Ar⁶⁵Cu⁺ and ⁸⁹Y¹⁶O⁺ on ¹⁰⁵Pd and ⁴⁰Ar⁶³Cu⁺, ⁸⁷Rb¹⁶O⁺, ⁸⁷Sr¹⁶O⁺ and ²⁰⁶Pb²⁺ on ¹⁰³Rh, were considered and mathematically corrected. The sampling procedure was applied to quantify the PGE released from two different types of fresh gasoline catalyst (Pt/Pd/Rh and Pd/Rh), a diesel catalyst (Pt only) and a 18 000 km aged Pt/Pd/Rh gasoline catalyst. Most of the released PGE is in particulate form (Pt >95%, Pd >85% and Rh >90%). Release was found to vary from catalyst to catalyst and between samples of the same catalyst. The determination of PGE in the exhaust fumes shows that they are released at the ng km^–1 level.

References

1. L. A. Carol, N. E. Newman and G. S. Mann, SAE paper 892040, 1989.
2. J. C. Summers, W. B. Williamson and J. A. Scaparo, SAE paper 900495, 1990.
3. G. C. Koltsakis and A. M. Stamatelos, Prog. Energy Combust. Sci., 1997, 23, 1.
4. G. Rosner and R. Merget, in Allergenic Potential of Platinum Compounds. Immunotoxicity of Metals and Immunotoxicology, ed. A. Dayan, R. F. Hertel, E. Hesseltine, G. Kazautzis, E. H. Smith and M. T. Van der Venne, Plenum Press, New York, 1990, pp. 93.
5. R. Merget, G. Schultze-Werninghans, F. Bode, E. Bergmann, W. Zachgo and Y. Meier-Sydow, Br. J. Ind. Med., 1991, 48, 830.
6. D. P. Moon and J. R. Donald, UK Research Programme on the Characterisation of Vehicle Particulate Emissions—ETSU-R98, September 1997.
7. H. P. König, R. F. Hertel, W. Koch and G. Rosner, Atmos. Environ., 1992, 26A, 741.
8. S. Knobloch, H. König and G. Wünsch, in Application of Plasma Source Mass Spectrometry II, ed. G. Holland and A. N. Eaton, The Royal Society of Chemistry, Cambridge, 1993, pp. 108–114.
9. R. F. Hill and W. J. Mayer, TEEE Trans. Nucl. Sci., 1977, NS-24, 2549.
10. C. Lüdke, E. Hoffmann, J. Skole and S. Artelt, Fresenius' J. Anal. Chem., 1996, 355, 261.
11. E. Helmers, Environ. Sci. Poll ut. Res., 1997, 4(2), 100.
12. F. Zereini, F. Alt, K. Rankenburg, J. Beye and S. Artlet, Z. Umweltchem.Ökotox., 1997, 9, 193.
13. O. V. Borisov, D. M. Coleman and R. O. Carter III, J. Anal. J. Spectrom., 1997, 12, 231.
14. E. H. Evans and J. J. Giglio, J. Anal. J. Spectrom., 1993, 8, 1.
15. R. F. J. Dams, J. Goosens and L. Moens, Mikrochim. Acta, 1995, 119, 277.
16. FINNIGAN MAT GmbH, ICP-MS Interference Table, 1995.
17. M. Parent, H. Vanhoe, L. Moens and R. Dams, Talanta, 1997, 44, 221.