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J. Anal. At. Spectrom., 2008, 23, 298 - 308, DOI: 10.1039/b710808g

Characterization of candidate reference materials for bone lead via interlaboratory study and double isotope dilution mass spectrometry

David J. Bellis, Katherine M. Hetter, Mary Frances Verostek and Patrick J. Parsons

Four candidate ground bone reference materials (NYS RMs 05-01 through 04), were produced from lead-dosed bovine and caprine sources, and characterized by interlaboratory study. The consensus value (X) and expanded standard uncertainty (UX) were determined from the robust average and standard deviation of the participants data for each NYS RM 05-01 through 04. The values were 1.08 ± 0.04, 15.3 ± 0.5, 12.4 ± 0.5, and 29.9 ± 1.1 µg g-1 Pb, respectively. Youden plots of z-scores showed a statistically significant correlation between the results for pairs of NYS RM 05-02 through 04, indicating common sources of between-laboratory variation affecting reproducibility. NYS RM 05-01 exhibited more random variability, affecting repeatability at low concentration. Some participants using electrothermal atomic absorption spectrometry (ETAAS) exhibited a negative bias compared to the all-method consensus value. Other methods used included inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution (ID-) ICP-MS, and ICP atomic (optical) emission spectroscopy (-OES). The NYS RMs 05-01 through 04 were subsequently re-analyzed in house using double ID-ICP-MS to assign certified reference values (C) and expanded uncertainty (UC) of 1.09 ± 0.03, 16.1 ± 0.3, 13.2 ± 0.3 and 31.5 ± 0.7, respectively, indicating a low bias in the interlaboratory data. SRM 1486 Bone Meal was analyzed for measurement quality assessment, obtaining results in agreement with the certified values within the stated uncertainty. Analysis using a primary reference method based on ID-ICP-MS with full quantification of uncertainty calculated according to ISO guidelines provided traceability to SI units.

Graphical abstract image for this article (ID: b710808g)