An interlaboratory comparison of bone lead measurements via K-shell x-ray fluorescence

Bone lead measurements assess chronic exposure and can be obtained via a noninvasive analytical technique based on K-she 11 x-ray fluorescence (KXRF) spectrometry. While KXRF has been practiced by a number of laboratories around the world, this technique has not, until now, undergone an assessment of interlaboratory agreement. The study described here provides such an assessment via circulation of nine bare tibiae selected from a repository of bones that were derived from lead-dosed goats. Fifteen KXRF systems were used by ten participating laboratories, to make five measurements on each of the nine caprine tibiae. Reported bone lead concentrations ranged from the KXRF detection limit to 63 μg g^-1 bone mineral. None of the data from the ten participant laboratories was found to be a statistical outlier. However for each of the nine tibiae, differences between the 15 reported bone lead concentrations were statistically significant. The standard deviations of the five replicate KXRF-measured concentrations ranged, across all laboratories and all tibiae, from 0.5 to 6.5 μg g^_1, bone mineral.