DETERMINATION OF TRACE-METALS IN TEETH AND BONES BY SOLUTION NEBULIZATION ICP-MS

This paper presents analytical quality data for the determination of m etals in calcified tissues by solution ICP-MS. Because of the extremel y low levels of metals in teeth and bones, preferred sample digest con centrations for ICP-MS analysis are >0.5% (w/v). At these concentratio ns, hydroxy-apatite, the dominant constituent of teeth and bone, cause d significant signal suppression of most metals (41-75% at 1.2% w/v), increasing with mass number and sample weight. The signals of the two most abundant isotopes of Ni, however, were enhanced by hydroxyapatite at sample wts of 1-3%, probably due to the formation of polyatomic Ca oxide ions in the plasma. Analyses of bone reference material and of teeth from wild mammals indicated that isotope dilution produced more accurate and precise Cd data than other techniques. However, during mo derate to severe Ca buildup on sampler and skimmer cones, unpredictabl e variations occurred in the isotopic ratios of Cd. While the explanat ion for these variations is uncertain, they are a useful diagnostic of intra-instrument Ca buildup and of the need to reanalyze the samples in question. With bone matter, external calibration with internal stan dardization provided good quality data for Pb and Sr (based on accurac y and precision), and for other metals (based on precision alone), but not for Ni because of Ca related spectral interferences. External cal ibration alone is not recommended for elemental determinations in thes e types of matrices because of severe instrument drift related to the high solids concentrations in digests.