L-shell x-ray fluorescence measurements of lead in bone: accuracy and precision

Abstract

This study aimed to quantify the accuracy and precision of a method for in vivo measurements of lead in bone using L-shell x-ray fluorescence (LXRF), the former via comparison with independent measurements of lead in bone obtained using electrothermal atomic absorption spectrometry (AAS) following acid digestion. Using LXRF. the lead content of adult human cadaver tibiae was measured, both as intact legs and as dissected tibiae with overlying tissue removed, the latter at several proximal-distal locations. After LXRF, each tibia was divided into nine cross-sectional segments, which were further separated into tibia core and surface samples for AAS measurement. The proximal-distal variability of AAS-measured core and surface tibia lead concentrations has been described elsewhere (the lead concentration was found to decrease towards both ends of the tibia). The subjects of this paper are the proximal-distal variability of the LXRF-measured lead concentrations, the measurement uncertainty and the statistical agreement between LXRF and AAS. There was no clear proximal-distal variability in the LXRF-measured concentrations; the degree of variability in actual tibia lead concentrations is far less than the LXRF measurement uncertainty. Measurement uncertainty was dominated by counting statistics and exceeded the estimate of lead concentration in most cases. The agreement between LXRF and AAS was reasonably good for bare bone measurements but poor for intact leg measurements. The variability of the LXRF measurements was large enough, for both bare bone and intact leg measurements, to yield grave concerns about the analytical use of the technique in vivo.

A Critical Review of Biomarkers Used for Monitoring Human Exposure to Lead: Advantages, Limitations, and Future Needs

“…The result is emission of X-ray photons that are characteristic of Pb. Measurements are performed by using one of four kinds of XRF: two involve fluorescence of the K-shell electrons of Pb (K-XRF), and the other two involve fluorescence of the L-shell electrons (L-XRF) (Todd et al 2002a). Several groups, mainly in North America, have reported the development of in vivo measurement systems; the majority have adopted the K-XRF approach based on excitation with a 109 Cd isotope and backscatter geometry because of its advantages: it provides a robust measurement with a better detection limit and a lower effective (radiation) dose (as compared to L-XRF) (Todd and Chettle 1994).…”

Atomic spectrometry and trends in clinical laboratory medicine

“…In this respect, the application of non-invasive techniques based on X-ray fluorescence (XRF) spectrometry has been shown to be particularly valuable in clinical studies, since in vivo measurements are feasible. However, most of these studies have been limited to the determination of Pb in bone using K-shell XRF [62][63][64]. While some uncertainties remain regarding the accuracy, repeatability, and traceability of bone Pb measurements by KXRF, these are expected to be resolved, as new matrix-based reference materials become available that are traceable to the fundamental SI unit of measurement.…”

A importância da análise de especiação do chumbo em plasma para a avaliação dos riscos à saúde

“…A concordância entre FRXL e ET AAS foi razoavelmente boa para o osso exposto, mas pobre para a perna ínte-gra. A variabilidade das medidas por FRXL foi grande para ambas as amostras, o que gera sérias suspeitas sobre o seu uso analítico in vivo 64 . A protoporfirina eritrocitária é uma parte das células vermelhas que aumenta quando a quantidade de chumbo no sangue é elevada.…”