In recent years the air quality in the vicinity of motorways has improved due to the distinct reduction of hazardous car emissions such as VOC, CO and NO_x thanks to the introduction of catalytic converters for exhaust gas. The investigation on the distribution and speciation o PGE (Platinum group elements) is of central interest, since the operation of any car equipped with catalytic converters lead to the emission of Pt, Pd and Rh in nanogram quantities per each km driven. The measurement of Pd in environmental samples by ICP-MS suffers from molecular interferences e.g. by Sr, Y, Mo and Zr with O and N. The new Varian 820 ICP-MS equipped with a CRI (collision reaction interface) allows reducing these sorts of interferences by two to three orders of magnitudes.
In the figure we see the dominant intensity of the interfering molecules in the regular measuring mode (blue) when the interfering elements are present in 100 fold higher concentrations than the elements of interest. When the collision cell is activated the isotopes of Pd (red) can be measured almost free of interferences despite the presence of disturbing elements. This can be seen best on mass 107 where we see no remaining signal, since Pd has no isotope of this mass.

This work was carried out by Kaizhen Li, Meena Zala and Christian Stenger in the group of Prof. Urs Krähenbühl.

References:

• For additional informations see:
  Varian ICP-MS Application Notes Number 28 / 29 / 30 / 31.