Maria Alexandra Barreiros

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.

Study of heavy metals in Madeira wine by total reflection X‐ray fluorescence analysis

The suitability and high sensitivity of total-reflection x-ray fluorescence analysis (TXRF) were used for multielement analysis of several species of Madeira wine taken directly from the usual glass bottles. In addition, the uptake of lead by Madeira wine kept in a crystal vessel (30% lead) as a function of time was also studied. The detection limits were in the range 0.001-0.10 mg l -1 and the precision was in the range 5-10%. The organic matrix of the wine was removed by wet digestion in nitric acid.

Application of different techniques to assess sediment quality and point source pollution in low-level contaminated estuarine recent sediments (Lisboa coast, Portugal)

Abstract Several X-ray techniques have been used in order to consider the chemical and mineralogical characterisation of recent superficial clay—silty sediments collected from the coastal shelf of the Atlantic Ocean, near Lisboa. Multi-element analyses have been carried out by means of total reflection X-ray fluorescence (TXRF) and radioisotope induced X-ray fluorescence (RIXRF). Mineralogical composition was determined using X-ray diffraction (XRD) methods. Particle size distribution was determined by means of a laser scattering technique. Statistical data treatment (correlation matrix, regression and factorial analysis) was used to identify elemental affinities and relationships among chemistry, mineralogy, texture and geographical distribution. The elements Ni, Cu, As and Pb show a marked relationship with clay minerals whose content is also correlated with the decreasing grain-size. Ti, Mn, Zr and V are grouped and may be related to the iron oxide content. Carbonates, Ca, Sr and quartz are correlated with the coarser grain-size fraction.

Application of Total Reflection XRF to Elemental Studies of Drinking Water

The aim of this work was to study the water quality, especially metallic pollution, at water treatment plants and inside buildings. The samples were collected in two regions of Portugal and in one of these regions water collection was also made inside houses chosen according to their type of plumbing, in order to compare its influence on metal concentrations in the drinking water. The analyses were carried out by total-reflection x-ray fluorescence without sample preconcentration. The detection limits were in the range 0.5-1.7 μg l -1 for Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Hg and Pb and 4.9-11 μg l -1 for K, Ca, V, Cd, Sb and Ba.

Quality assurance of X-ray spectrometry for chemical analysis

Abstract Three different techniques, energy dispersive X-ray fluorescence, total reflection X-ray fluorescence and particle induced X-ray emission were used to initiate an evaluation program on quality assurance (QA) procedures applied to X-ray spectrometry for chemical analysis. The use of standard methodologies to assure the statistical control of measurement data is the main objective of this work. Certified Reference Materials were used and up to 15 certified elements were analyzed to carry out the QA procedures. For the internal quality control, z -scores were calculated and control charts were produced. The plotted elemental data illustrate statistically controlled methodologies for the majority of the determinations. Even the cases where the control charts exhibit values out of control limits, the z -scores are below 3 in absolute value, indicating satisfactory results. Concerning external quality control the statistical methods applied showed that the results obtained for the three techniques are comparable, although some significant differences occur, mainly due to sample preparation. Therefore, the techniques are traceable to certified reference materials and the data gathered so far, enable to initiate a database for QA procedures.

Microprobe analysis of teeth by synchrotron radiation: environmental contamination

Abstract An X-ray fluorescence set-up with microprobe capabilities, installed at the Laboratoire pour l’Utilisation du Rayonnement Electromagnetique (LURE) synchrotron (France) was used for elemental determination in teeth. To evaluate the influence of living habits in dental elemental composition nine teeth collected post-mortem were analysed, five from a miner and four from a fisherman. All teeth from the fisherman were healthy. From the miner some teeth were carious and one of them was filled with metallic amalgam. Teeth were sliced under the vertical plane and each slice was scanned from the root to the enamel for elemental profile determination. The synchrotron microprobe resolution was of 100 μm and incident photons of 18 keV energy were used. The elemental concentration values found suggest heterogeneity of the teeth material. Moreover, the distinct profiles for Mn, Sr, Br and Pb were found when teeth from the miner and from the fisherman are compared which can be associated with dietary habits and environmental influence. Higher concentrations of Mn and Sr were found for the fisherman teeth. In addition, Br was only observed in this group of teeth. Pb levels are higher for the miner teeth in particular for dentine regions. The influence of amalgam, such as, increase of Zn and Hg contents in the teeth material, is only noticed for the immediate surroundings of the treated cavity.

Multi-element characterization of estuarine sediments and waters

Trace elements were studied in the sediments and waters of the Atlantic Ocean, under the influence of Tagus river estuary, near Lisbon (Portugal). Elemental concentrations of Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Zr and Pb, were determined by total reflection X-ray fluorescence (TXRF), in surface recent sediments (fraction <63 μm) and bottom waters at 20 sampling sites. A comparison was made between the results obtained and the recommended values given in the literature for estuarine sediments and also for ocean waters and concentration factors (sediment/water elemental concentrations). This study showed high concentrations for As and Pb, in sediments and an enrichment for all the elements determined in waters, although the concentration factors were always below the recommended values, except for Fe and As.

Amalgam components drift in teeth-toxicity risks: A preliminary approach

Abstract The use of ion beam techniques applied to teeth studies have been extensive in what concerns the major elements distribution. However, it is not clarified whether amalgam components are absorbed and drifted through teeth material, although the toxicity of the elements used in amalgams, such as Hg, are well known. This work is an attempt to assess a possible teeth contamination originated by the amalgams. Therefore, teeth with metallic amalgam, as well as healthy ones, were studied. The teeth were longitudinally cut and each slice was scanned from the inner region to the surface enamel for elemental profiles determination purposes using Particle Induced X-ray Emission (PIXE) and Synchrotron Radiation X-ray Fluorescence (SRXRF) techniques. High levels of Zn, Ag, Sn, Hg and Pb were found along the scanned teeth restored with the metallic amalgam. The elemental distribution patterns suggest diffusion of these elements in the teeth material from amalgam constituents.

Biomarkers of Exposure to Metal Dust in Exhaled Breath Condensate: Methodology Optimization

ABSTRACT In occupational assessments where workers are exposed to metal dust, the liquid condensate of exhaled breath (EBC) may provide unique indication of pulmonary exposure. The main goal of this study was to demonstrate the quality of EBC to biological monitoring of human exposure. A pilot study was performed in a group of metal dust–exposed workers and a group of nonexposed individuals working in offices. Only metal dust–exposed workers were followed along the working week to determine the best time of collection. Metal analyses were performed with inductively coupled plasma mass spectrometry (ICP-MS). Analytical methodology was tested using an EBC sample pool for several occupationally exposed metals: potassium, chromium, manganese, copper, zinc, strontium, cadmium, antimony, and lead. Metal contents in EBC of exposed workers were higher than controls at the beginning of the shift and remained augmented throughout the working week. The results obtained support the establishment of EBC as an indicator of pulmonary exposure to metals.

Exhaled breath condensate as a biomonitor for metal exposure: a new analytical challenge

The study of exhaled breath condensate (EBC) obtained by cooling exhaled air under conditions of spontaneous breathing is considered one of the areas with higher interest in respiratory health research. The use of EBC for elemental determination in occupational exposure requires a standard methodological procedure to implement its practice in occupational studies. EBC is an inhomogeneous sample with organic and particulate matter in suspension, which may hamper analytical results reliability. Total reflection X-ray fluorescence and inductive coupled-plasma mass spectrometry (ICP-MS) techniques were chosen as both are multielemental, require small sample volumes and have appropriate detection limits. Estimation of the overall uncertainty in both techniques was carried out using a pool of EBC collected from a group of workers of a lead processing industry to perform precision and trueness studies for K, Mn, Cu, Cd, Sb and Pb. Precision was estimated in terms of repeatability using the native EBC sample pool and trueness in terms of recovery obtained from spiking aliquots of the EBC pool with K, Mn, Cu, Cd, Sb and Pb at different concentrations. Recovery was the most significant contribution to total uncertainty. The overall uncertainties obtained for ICP-MS enabled to discriminate between groups of individuals exposed to different levels of contaminants. Therefore EBC proved to be useful in human biomonitoring.