Platinum-group element concentrations in BCR-723: a quantitative review of published analyses

BCR-723 is the only environmental certified reference material for platinum-group elements (PGEs) Pt, Pd and Rh. It has been an integral component of quality control/quality assurance procedures in environmental laboratories measuring PGEs, since 2001. Here, we present an extensive quantitative review of the published PGEs measured in BCR-723, since its introduction. A statistical examination of concentrations, measurement precision and accuracy for 25 studies is presented. Measurement typically starts with an aqua regia digestion, followed by some form of pre-concentration or separation procedure, and quantitation by ICP-MS. Use of a sample mass below the recommended value of 100 mg has been shown to produce biased results for acid-based digestions or with laser ablation. Platinum is the most precisely and accurately measured PGE in BCR-723, followed by Rh, and finally by Pd. Literature precision data for all autocatalyst PGEs did not differ significantly (alpha=0.05) from those obtained by the original laboratories used to certify BCR-723. Measurement accuracies for the literature tabulated PGE data did not differ significantly from zero, indicating an overall lack of directional bias. These results should be encouraging to the analytical community, but further advancements, especially for Pd quantification are required.