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A highly sensitive, catalytic adsorptive stripping voltammetric procedure at the hanging mercury drop electrode for the simultaneous determination of ultratraces of platinum and rhodium in electrolyte solutions has been evaluated. Optimal conditions were found to be: first accumulation potential 0 V (vs. Ag/AgCl), second accumulation potential −0.8 V, first preconcentration time 90 s, second preconcentration time 120 s, scan rate 20 mV s−1. The response of the system was found to be linear in a range of platinum concentrations up to 6 ng l−1 and for rhodium up to 0.5 ng l−1. The detection limit was 21 pg l−1 for platinum and 5.6 pg l−1 for rhodium. The effect of various possible interferences from other metal ions was also studied. With the exception of zinc (whose influence was studied in more detail), no significant interferences were observed. The method was successfully applied to the determination of traces of Pt and Rh in real environmental samples (spruce shoots) after high pressure digestion.

Differential pulse cathodic stripping voltammetry (DPCSV) was used to determine ultra trace platinum in gasoline after Wickbold combustion and subsequent UV digestion. A commercially available Wickbold combustion apparatus was slightly modified and used to mineralize the gasoline samples. Because a sufficiently high chloride concentration is necessary to avoid Pt losses, the chloride concentration in the condensate was increased by adding HCl vapor to the oxygen stream. The sample solution obtained from the Wickbold combustion still contained some organic compounds which were eliminated using an UV digestion (T > 90 °C, t > 90 min) prior to the electrochemical determination. The recovery was > 87% Platinum concentrations in the order of 5 pg g−1 were found in the analyzed gasoline samples (unleaded Normal, Super and Super Plus). Inductively coupled plasma mass spectrometry was used for comparative measurements.