M.L. Carvalho

Cathodic and anodic biofilms in single chamber microbial fuel cells

The oxygen reduction due to microaerophilic biofilms grown on graphite cathodes (biocathodes) in Single Chamber Microbial Fuel Cells (SCMFCs) is proved and analysed in this paper. Pt-free cathode performances are compared with those of different platinum-loaded cathodes, before and after the biofilm growth. Membraneless SCMFCs were operating in batch-mode, filled with wastewater. A substrate (fuel) of sodium acetate (0.03 M) was periodically added and the experiment lasted more than six months. A maximum of power densities, up to 0.5 W m(-2), were reached when biofilms developed on the electrodes and the cathodic potential decreased (open circuit potential of 50-200 mV vs. SHE). The power output was almost constant with an acetate concentration of 0.01-0.05 M and it fell down when the pH of the media exceeded 9.5, independently of the Pt-free/Pt-loading at the cathodes. Current densities varied in the range of 1-5 Am(-2) (cathode area of 5 cm(2)). Quasi-stationary polarization curves performed with a three-electrode configuration on cathodic and anodic electrodes showed that the anodic overpotential, more than the cathodic one, may limit the current density in the SCMFCs for a long-term operation.

Analysis of human teeth and bones from the chalcolithic period by X-ray spectrometry

Abstract Synchrotron microprobe and X-ray fluorescence spectrometry (XRFS) were used to analyse several teeth and pieces of bone, respectively, originating from subjects of the chalcolithic period. A synchrotron microprobe with 100 μm resolution and monochromatic photons of 18 keV were used to scan teeth from the root to the enamel. Bones were analysed by XRFS for their amount of trace elements, using a spectrometer based on a three-axial geometry and an incident beam of 17.4 keV. The detected elements for both analytical procedures were P, K, Ca, Mn, Fe, Cu, Zn, Br, Sr and Pb. The results show high concentrations of Mn, Fe and Cu for different tooth regions when compared with data from contemporary subjects. Moreover, the high levels of Br and Sr can be associated with environment influence and dietary habits rich in protein, especially seafood. It is remarkable that lead is always of the order of magnitude of the detection limit, which is 1–2 μg/g in all analysed teeth. Furthermore, the microprobe analysis of these samples showed that the highest concentration of the heavy metals increases from the outer enamel to the inner dentine root. For the analysed bone samples of women and men, the most important aspects concerning the elemental concentrations are the high levels of Mn and Br and the low concentrations of Pb, as found for teeth.

Heavy metals in soft tissues of Tursiops truncatus and Delphinus delphis from west Atlantic Ocean by X-ray spectrometry

In this work, the concentration of heavy metals in muscle, liver, fat tissue and skin is studied in 15 Delphinus delphis and two Tursiops truncatus dolphins, stranded along the Portuguese coast of the Atlantic Ocean. Sample collection was performed post-mortem and the tissues were kept frozen until analysed. Sample preparation included lyophilising and grounding in a Teflon mill to avoid contamination by metals. The obtained powder was prepared as pellets for each sample and analysed directly by X-ray fluorescence spectrometry. The concentrations of K, Ca, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Hg and Pb were obtained. Significant differences between the muscle, the skin and the fat tissues were detected. Cobalt concentrations were similar in liver, skin and muscle. The levels of Ni, Rb and Sr are at the level of the detection limit and whenever measurable are rather constant in all the analysed tissues. The results show that the highest concentrations of Mn, Cu and Hg are always in liver tissues. Zinc and Se concentrations are higher in skin and Pb is present in very low concentrations in all the analysed tissues except in skin; Fe and As are enhanced in muscle and liver. In general, the two studied species did not seem to differ significantly in their heavy metals concentration in a given tissue.

Noninvasive and nondestructive NMR, Raman and XRF analysis of a Blaeu coloured map from the seventeenth century

A complete multianalytical study of a hand-coloured map from the seventeenth century is presented. The pigments atacamite, massicot, minium, gypsum, carbon black and vermilion were determined by means of XRF and Raman spectroscopy. The state of conservation of the cellulosic support was monitored by means of unilateral NMR. The analysis was nondestructive and noninvasive, and thus several spectra were collected from the same areas, yielding more reliable results without damaging the artwork. The role of copper pigments in the oxidation processes observed in the cellulosic support is discussed, as well as the possible provenance of atacamite as a raw material instead of as a degradation product of malachite.

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.

Analysis of a coloured Dutch map from the eighteenth century: the need for a multi-analytical spectroscopic approach using portable instrumentation.

A Dutch map from the eighteenth century was multi-analytically analysed making use of energy dispersive X-ray fluorescence (EDXRF), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), Raman and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS). The cellulosic support was characterised and its state of conservation was evaluated. Besides, paramagnetic impurities were detected together with copper metallic chips. The colours present in some areas of the map were also analysed. Vermilion, carbon black and organic pigments were found. Surprisingly, in the green areas, the rare presence of the mineral moolooite (copper oxalate) was detected. A possible biological attack is discussed in order to explain the presence of such compound. Almost all of the techniques used in the analysis were portable, non-destructive and non-invasive, which is very desirable when analysing objects belonging to Cultural Heritage. The need for a multi-analytical approach using portable instrumentation is also discussed.

Nutritional quality and safety of cooked edible crab (Cancer pagurus).

Edible crab (Cancer pagurus) is one of the most important crustaceans consumed in Southern European countries, either as boiled or steamed cooked product. So far, the majority of studies assessing health benefits and risks associated to seafood consumption have been carried out in raw products, despite being generally cooked before consumption, and mostly in muscle tissue. Therefore, the aim of this study was to assess the effect of steaming and boiling on the chemical safety and nutritional value of C. pagurus caught in spring and summer. Generally, chemical and elemental composition of brown meat (tissue in the body cavity comprising mainly gonads and hepatopancreas) differed significantly from muscle (white meat in claws and legs). Additionally, the same tissue revealed differences in chemical and elemental composition of raw and cooked C. pagurus, likely due to water leaching. In contrast, few variations between seasons were observed. The results revealed that the consumption of cooked edible crab muscle should be promoted, whereas brown meat ingestion should be done parsimoniously.

Elemental identification of document paper by X-ray fluorescence spectrometry

The use of the elemental composition, determined by energy dispersive X-ray fluorescence (EDXRF), to identify different sorts of paper is reported. The concentrations of K, Ca, Ti, Mn, Fe, Cu, Zn, Rb, Sr and Ba were determined in sheets of an Italian book from 1941 with 200 pages. A dendrogram based on the elemental composition of each sheet, demonstrated three major groups of paper. Each group is formed by more than one paper block. This information allowed the box plotting for the three clusters which demonstrate the different elemental composition between the clusters and the identification of each of them. Cluster 1 could be identified by any of the concentrations of Ca, Cu, Zn and Ti, cluster 3 was identified by the concentration of Ba and Sr, while cluster 2 could be identified by considering all the elements together. These statistical results allowed us to conclude that this document was manufactured with three different kinds of paper. Applying Spearman coefficient correlations, strong positive correlations were found between K–Ca, Ti–Ca, Mn–Fe and Sr–Ba in the paper of cluster 1. For cluster 2 high positive correlation was observed between Ca–Fe and strong negative correlations were obtained between Ca–Sr and Fe–Sr. For the third cluster only a positive correlation was observed between Sr–Ba. Applying the Spearman coefficient correlations to the whole book, no correlations were observed. These results confirm the assumption that papers can be characterized using trace elemental concentration.

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.

Characterisation of foxing stains in eighteenth to nineteenth century drawings using non-destructive techniques

The reddish-brown, brown or yellowish stains of circular or irregular shape known as foxing spots have been fully described in conservation literature but still, this phenomenon does not find any scientific agreement since many hypotheses have been raised concerning their origin. In this work a contribution to foxing definition not only focussed on its appearance but also reported on its chemical information. For this purpose foxing stains present in drawings from two Portuguese artists dated from the eighteenth to nineteenth centuries were observed under ultra-violet light and optical microscope and analysed by three non-invasive spectroscopy techniques. The observations carried out on the stains provided information on their surface morphology. The use of energy-dispersive X-ray fluorescence revealed a variation on the elemental content between foxing and paper region. Although the results from X-ray diffraction analysis showed no signs of cellulose degradation in foxing stains, Fourier-transformed infrared analysis revealed the presence of oxide groups. Both the information on the chemical nature and surface morphology of the stains achieved in this study will contribute to increase foxing formation information and develop future protocols for conservation purposes.