Pure and Applied Chemistry

Over the past decade, the increasing use of car catalytic converters based on platinum-group elements (PGEs) has been raising more and more concern. Human exposure to these metals occurs indirectly also through the diet. Thus, a pilot investigation was undertaken in order to ascertain the actual intake of PGEs through bread and cow milk. All manipulations were performed in a Class-100 clean room so as to minimize the risk of sample contamination. Digestion of samples was achieved by means of a mixture of HNO₃ and H₂O₂ with the assistance of microwave irradiation.

Determinations were performed by sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) to quantify Pd, Pt, and Rh. The isotopes ¹⁰⁵Pd⁺, ¹⁰³Rh⁺, and ¹⁹⁵Pt⁺ were used for the quantification. Major interferences were caused by ⁴⁰Ar⁶⁵Cu⁺ on ¹⁰⁵Pd⁺, ¹⁷⁹Hf¹⁶O⁺ on ¹⁹⁵Pt⁺, and ⁸⁷Rb¹⁶O⁺ and ⁸⁷Sr¹⁶O⁺ on ¹⁰³Rh⁺. Both physical and mathematical approaches for the interference correction were used. The mean values for PGEs were found to be as follows (in ng kg^-1): full-cream milk: Pd, 3790; Pt, 83.2; Rh, 1680; skim milk: Pd, 12 400; Pt, 83.6; Rh, 1090; wholemeal bread: Pd, 3210; Pt, 171; Rh, 139; white bread: Pd, 27 400; Pt, 257; Rh, 2230. The preliminary data obtained in this study are probative of the significant portion of the total exposure to PGEs, which is due to the diet.