Accurate and precise measurements of lead in bone using electrothermal atomic absorption spectrometry with Zeeman-effect background correction

Abstract

A simple method for measuring trace levels (µg g^–1) of Pb in bone by electrothermal atomic absorption spectrometry (ETAAS) is described. ETAAS instrumentation equipped with a transverse Zeeman-effect background correction system was used to investigate the effects of bone matrix on Pb atomization. It is shown that Pb can be accurately measured with good precision using aqueous Pb standards containing NH₄H₂PO₄ modifier and Ca(NO₃)₂. Alternatively, Mg(NO₃)₂ works as well as Ca(NO₃)₂. For rapid and contamination-free sample preparation, bone was digested in concentrated HNO₃ using a closed-vessel microwave digestion system. This approach was compared with digestion at room temperature over 48 h. The detection limit (3s) is 0.6 µg g^–1 dry mass. Typical day-to-day precision is < 5%. Method accuracy is established as better than 1% using NIST SRM 1400 Bone Ash and SRM 1486 Bone Meal, which are the only reference materials we have found for bone-Pb measurements. The method was used to analyse various bone specimens (e.g., tibia, femur, rib and skull) from Pb-dosed animals. Results indicate that Pb is heterogeneously distributed within bone.