Determination of Pt, Pd and Rh in biological samples by electrothermal atomic absorption spectrometry as compared with adsorptive cathodic stripping voltammetry and total-reflection X-ray fluorescence analysis

In the present study, we evaluated a microwave digestion procedure followed by electrothermal atomic absorption spectrometry (ET-AAS) for the determination of the platinum group metals (PGM) Pt, Pd and Rh in small amounts of animal tissue. Due to the lack of certified biological standard reference materials for PGM, we performed interlaboratory comparisons using adsorptive cathodic stripping voltammetry (ACSV) after digestion of the samples by high pressure ashing (HPA) for the determination of Pt and Rh and total-reflection X-ray fluorescence (TXRF) analysis after co-precipitation of Pd with mercury for the determination of Pd, as reference methods. Suitable sample materials were obtained from laboratory experiments with mussels exposed to PGM salts or ground automobile catalytic converter material. The 3 s detection limits for microwave digestion (MWA)/ET-AAS were 270 ng g-1 (Pt), 90 ng g-1 (Pd) and 13 ng g-1 (Rh), the precision was better than 10% and the recovery was >95%. The highest divergence between the MWA/AAS and HPA/ACSV/TXRF procedures was found for Pt with values of 48 and 26%. But, even though the Pt levels exceeded the detection limit, the concentrations were near to or below the limit of determination (three times the detection limit). In contrast to Pt, the results of the different analytical procedures for Pd and Rh were comparable (<20% deviation). The combination of MWA and ET-AAS is a very rapid and relatively cheap method for routine PGM analysis in large numbers of animal tissue samples with PGM concentrations exceeding the upper ng g-1 range as occur e.g. in experimental studies or in the medical sector after treatment with Pt-anti-cancer drugs