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Certification of the mass fractions of Pt, Pd and Rh in a used car catalyst reference material
(2009)
The high economic value of catalysts containing the platinum group elements platinum, rhodium and palladium as active components causes the need to be able to measure the precious metal loading with small uncertainty and to have suitable certified reference materials fulfilling high demands on the quality of the certified values. In European Reference Material ERM®-EB504, a used cordierite-based car catalyst material, mass fractions of platinum, palladium and rhodium were certified. The raw material was milled, homogenised and annealed before analysis. Seventeen laboratories experienced in precious metals analysis participated in the certification interlaboratory comparison, most of them analysing with inductively coupled plasma optical emission spectrometry using different sample pretreatment techniques. Homogeneity testing was carried out using X-ray fluorescence spectrometry. The certified mass fractions of Pt, Pd and Rh and their expanded uncertainties (k = 2) in ERM®-EB504 are (1777 ± 15), (279 ± 6) and (338 ± 4) mg/kg respectively.
The EU RoHS Directive (2002/95/EC of the European Parliament and of the Council) bans the placing of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants on the EU market. It necessitates methods for the evaluation of RoHS compliance of assembled electronic equipment. In this study mounted printed circuit boards from personal computers were analyzed on their content of the three elements Cd, Pb and Hg which were limited by the EU RoHS directive. Main focus of the investigations was the influence of sample pre-treatment on the precision and reproducibility of the results. The sample preparation steps used were based on the guidelines given in EN 62321. Five different types of dissolution procedures were tested on different subsequent steps of sample treatment like cutting and milling. Elemental analysis was carried out using ICP–OES, XRF and CV–AFS (Hg). The results obtained showed that for decision-making with respect to RoHS compliance a size reduction of the material to be analyzed to particles ≤1.5 mm can already be sufficient. However, to ensure analytical results with relative standard deviations of less than 20%, as recommended by the EN 62321, a much larger effort for sample processing towards smaller particle sizes might be required which strongly depends on the mass fraction of the element under investigation.