Characterization of calcified reference materials for assessing the reliability of manganese determinations in teeth and bone

Abstract

As interest increases in human biomonitoring for exposure to manganese (Mn) via analysis of bone and teeth, there is a growing need for calcified reference materials (RMs) certified for Mn content. Here, several existing calcified RMs and synthesized hydroxyapatite (HA) RMs were digested with acid and subsequently analyzed for Mn by graphite furnace atomic absorption spectrometry (GFAAS) and dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS). Based on GFAAS and DRC-ICP-MS results, mean values and expanded uncertainties were assigned to four New York State (NYS) Bone RMs (05-01 through 05-04), and six synthesized HA standards. Consensus values and expanded uncertainties for Mn content were assigned to NIST SRM 1400 Bone Ash (16.5 ± 2.3 μg g⁻¹) and NIST SRM 1486 Bone Meal (1.1 ± 0.5 μg g⁻¹) by combining GFAAS and DRC-ICP-MS results with literature values. These powdered RMs were also prepared for solid sampling techniques by pressing them into pellets for subsequent analysis by laser ablation (LA-) ICP-MS. The “dilution” effect from adding a chemical binder to the pellets was quantified by both GFAAS and DRC-ICP-MS, and the decrease in Mn mass fraction was found to be proportional to the amount of binder added. The distribution of Mn across the RM pellets was determined by LA-ICP-MS to assess homogeneity and suitability for use as solid standards. The bone RMs were more heterogeneous than the synthesized HA RMs, but the latter may be a less optimal matrix-match due to the absence of organic material.