Study of Trace Element Concentrations in Human Tissues by EDXRF Spectrometry

Human tissues (bone, hair, liver and kidney) from 61 individuals, collected post-mortem, were analyzed by energy-dispersive x-ray fluorescence (EDXRF) spectrometry. All samples were analyzed without any chemical treatment. The soft tissues (liver and kidney) were lyophilized and ground in an agate mortar whereas the hard tissues (bone and hair), after being lyophilized, were dried in an oven for 24 h at 200 °C prior to grinding. The samples were prepared by pressing the powder into pellets 2.0 cm in diameter. To investigate any possible contamination in the grinding procedure or loss of some elements due to the drying process, a few samples were analyzed by total reflection x-ray fluorescence. Levels of contamination of 1% for Fe and 3% for Cu and a loss of 19% for Se were introduced. To establish the accuracy and reproducibility of the technique, five targets of a standard reference material, NBS 1577a Bovine Liver, were examined. Each sample was studied for its content of Mn, Fe, Cu, Zn, Se, As, Sr, Rb and Pb in order to determine possible correlations between these elements in the different tissues. Variations in the concentrations of these elements with age and sex were also investigated in hard tissues. The elemental concentrations obtained for the studied elements are in reasonable agreement with those reported in the literature. Correlations among the elements for the different tissues were examined. For hair, a significant difference between male and female was found only for Zn. The Pearson correlation matrix, calculated to investigate the correlation between elemental concentrations and the dependence of these concentrations on age, showed that there is a negative correlation with age for Cu and Sr, although very weak. No significant correlations exist among the studied elements in hair, except for Fe and Cu. For bone samples, Zn, Sr and Pb present a significant positive correlation with age. The correlation among elements in bone is significant only for Fe and Cu. The results of the Pearson correlation matrix coefficients for elemental concentrations in hair and bone showed a significant correlation for Fe. The Pearson correlation matrix for soft tissues showed a positive correlation between Fe and Pb and a negative correlation between Zn and Pb in liver samples. The same test showed a strong positive correlation between Fe and Zn and between Cu and Zn and a weak significant correlation between Mn and Cu and between Rb and Pb in kidney.