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

Abstract

109Cd-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 tibiæ in which the mean lead value ranged from 4.0 µg g−1 to 55.3 µg g−1 bone mineral. The test tibiæ were subsequently analyzed via nitric acid digestion followed by lead determination by inductively coupled plasma mass spectrometry (ICP-MS) – 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 µg g−1 dry weight. The mean bone lead value based on ICP-MS analysis ranged from 1.8 µg g−1 to 35.8 µg g−1 dry weight. For comparison purposes, XRF-measured Pb values (µg g−1 bone mineral) were converted into the ICP-MS-measured units (µg g−1dry weight bone) by multiplying the former by the average ash fraction from the nine tibiæ. Eight of the XRF systems did not yield a significant bias for any of the nine tibiæ; one system was biased for one of the tibiæ; two systems were biased for two tibiæ; one system was biased for four tibiæ; two systems (813-1 and 804-2) were biased for five tibiæ and one system (801-1) was biased for six of the nine tibiæ. Average bias for the systems (under those particular operating conditions) that were biased for the majority of samples ranged from −2.6 µg g−1 (−15.7%) to 5.1 µg 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 tibiæ, to the extent of exceeding XRF variability for the higher lead values. Material heterogeneity is an unavoidable reality of measuring lead in bone.

Prenatal lead exposure modifies the association of maternal self-esteem with child adaptive ability

“…We used reference materials of plaster-of-Paris phantoms as targets for inter-calibration standards (Aro et al, 1994; Nie et al, 2004). Previous studies had validated K-shell X-ray fluorescence bone lead measurements by inductively coupled plasma mass spectrometry (Aro et al, 2000; Bellis et al, 2012; Weisskopf et al, 2010). Before the 30-minute measurements, the bone sites were cleaned with a 50% solution of isopropyl alcohol.…”

A hydroxyapatite phantom material for the calibration of in vivo x-ray fluorescence systems of bone strontium and lead quantification

“…dation studies. 36,[39][40][41][42][43][44] As a result, it has become the standard calibration procedure within the calibration protocol of most IVXRF-based systems for quantifying bone uranium, 22,23 strontium, 26,[45][46][47][48] lead via L-IVXRF 24,25,49,50 and 57 Co-induced K-IVXRF. 51 For IVXRF bone strontium measurements, the coherent normalization procedure developed for the K-IVXRF bone lead system, has been largely adapted with modifications including the use of poP-based calibrators/phantoms.…”

Atomic spectrometry update. Clinical and biological materials, foods and beverages

“…In previous ASUs, we have referred to work for in vivo measurement of Pb in bone using XRF and have highlighted various analytical and calibration problems associated with what is still a developing technique. Bellis et al 20 from the New York State Department of Health initiated an interlaboratory comparison study using tibia from their Pb-dosed goats. Nine samples were distributed with concentrations of 1.8-35.8 mg g À1 dw (measured by ICP-MS).…”

“…Yet, in contrast with the enormous amount of effort expended in developing interlaboratory comparison and prociency testing schemes to improve the measurement of Pb in blood, this review reports on the rst publication of work to compare the performance of different laboratory systems undertaking in vivo bone Pb measurements using XRF. Bellis et al 20 circulated samples of 9 goat tibiae to 15 laboratories performing bone Pb measurements with XRF instruments and who had agreed to participate in the exercise. The bone samples had mean Pb concentrations ranging between 1.8 mg g À1 and 35.8 mg g À1 Pb dw, as determined by a reference method using ICP-MS.…”