An interlaboratory comparison of bone lead measurements via K-shell X-ray fluorescence spectrometry: validation against inductively coupled plasma mass spectrometry

作者：Bellis David J; Todd Andrew C; Parsons Patrick J^*

来源：Journal of Analytical Atomic Spectrometry, 2012, 27(4): 595-603.

DOI：10.1039/c2ja10369a

Cd-109-based K-shell X-ray fluorescence spectrometry (hereafter, for brevity, XRF) is used, often in epidemiological studies, to perform non-invasive, in vivo measurements of lead in bone. We conducted the first interlaboratory study of XRF via the circulation of nine goat tibiae in which the mean lead value ranged from 4.0 mu g g(-1) to 55.3 mu g g(-1) bone mineral. The test tibiae were subsequently analyzed via nitric acid digestion followed by lead determination by inductively coupled plasma mass spectrometry (ICPMS) - along with certified reference materials for bone lead - thus providing measurement traceability to SI units. Analysis of dried bone for lead via nitric acid digestion and ICP-MS yields mass fraction data in units of mu gZ g(-1) dry weight. The mean bone lead value based on ICP-MS analysis ranged from 1.8 mu g g(-1) to 35.8 mu g g(-1) dry weight. For comparison purposes, XRF-measured Pb values (mu g g(-1) bone mineral) were converted into the ICP-MS-measured units (mu g g(-1) dry weight bone) by multiplying the former by the average ash fraction from the nine tibiae. Eight of the XRF systems did not yield a significant bias for any of the nine tibiae; one system was biased for one of the tibiae; two systems were biased for two tibiae; one system was biased for four tibiae; two systems (813-1 and 804-2) were biased for five tibiae and one system (801-1) was biased for six of the nine tibiae. Average bias for the systems (under those particular operating conditions) that were biased for the majority of samples ranged from -2.6 mu g g(-1) (-15.7%) to 5.1 mu g g(-1) (30.7%) dry weight bone. All participants now have the ICP-MS data, allowing any corrective actions deemed necessary to be implemented. The ICP-MS data, however, indicated that the lead mass fraction varied considerably with the sampling location within the tibiae, to the extent of exceeding XRF variability for the higher lead values. Material heterogeneity is an unavoidable reality of measuring lead in bone.

• 出版日期2012