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, ¹⁷⁹ Hf ¹⁶ O ⁺ on ¹⁹⁵ Pt, ⁴⁰ Ar ⁶⁵ Cu ⁺ and ⁸⁹ Y ¹⁶ O ⁺ on ¹⁰⁵ Pd and ⁴⁰ Ar ⁶³ Cu ⁺ , ⁸⁷ Rb ¹⁶ O ⁺ , ⁸⁷ Sr ¹⁶ O ⁺ and ²⁰⁶ Pb ²⁺ on ¹⁰³ Rh, 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.