Chapter 4 X-ray based methods of analysis

Zurbarán attribution hypothesis supported by pigment analysis and multiband images observation of four paintings by his workshop

Francisco de Zurbarán was one of the greatest painters of the Spanish Golden Age, with artworks scattered all over the world. Unfortunately, there are hardly any exhaustive studies on the pigments that he used. In this work, four canvas paintings attributed to the Zurbarán Workshop were studied. Each of them presents the figure of a different saint in a particular isolation scene: Saint Bruno, Saint Francis of Assisi, Saint Dominic of Guzman, and Saint Peter Martyr. Nevertheless, the painting of Saint Peter Martyr shows superior quality in both technique and colours, so it is not clear whether this canvas was also made by the Workshop or by Zurbarán himself, as some art historians claim. Coinciding with conservation and restoration works, the paintings were initially analysed with non-invasive techniques such as ultraviolet photography (UV), infrared reflectography (IRR) and X-ray fluorescence (XRF) to determine the characterization of the pigments. Those studies were complemented by stratigraphic analysis of some extracted samples with optical microscopy (OM) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Among a number of results obtained, we found significant differences between the pigment palette used in Saint Peter Martyr and the other paintings, supporting the hypothesis that this painting was done by Zurbarán himself instead of his workshop. These results could also help to distinguish other authentic paintings by the master's hand from very similar paintings by his workshop or by other artists.

Determination of La, Ce, Nd, Sm, and Gd in mineral waste from cassiterite beneficiation by wavelength-dispersive X-ray fluorescence spectrometry

The objective of this study was to establish the best parameters to correct for matrix effects in the chemical analysis of a siliceous geologic material rich in metallic elements of high economic value, such as La, Ce, Nd, Sm, and Gd (rare earth elements), using empirical influence coefficients applied to wavelength dispersive X-ray fluorescence (WDXRF). At present, this material is considered waste derived from the extraction of tin from cassiterite, a special ore from which niobium and tantalum are also processed. In this study, a reliable methodology for the analysis of rare earth elements in a siliceous matrix using the WDXRF technique was developed. This procedure may be useful in promoting industrial processes for chemical control in solid matrices, as the usual techniques are only possible in liquid media and require acid dissolution.

Textural and Mineralogical Analysis of Volcanic Rocks by µ-XRF Mapping

In this study, µ-XRF was applied as a novel surface technique for quick acquisition of elemental X-ray maps of rocks, image analysis of which provides quantitative information on texture and rock-forming minerals. Bench-top µ-XRF is cost-effective, fast, and non-destructive, can be applied to both large (up to a few tens of cm) and fragile samples, and yields major and trace element analysis with good sensitivity. Here, X-ray mapping was performed with a resolution of 103.5 µm and spot size of 30 µm over sample areas of about 5×4 cm of Euganean trachyte, a volcanic porphyritic rock from the Euganean Hills (NE Italy) traditionally used in cultural heritage. The relative abundance of phenocrysts and groundmass, as well as the size and shape of the various mineral phases, were obtained from image analysis of the elemental maps. The quantified petrographic features allowed identification of various extraction sites, revealing an objective method for archaeometric provenance studies exploiting µ-XRF imaging.

Effect of X-ray exposure on the pharmaceutical quality of drug tablets using X-ray inspection equipment

CONTEXT

X-ray inspection equipment is widely used to detect missing materials and defective goods in opaque containers. Its application has been expanded to the pharmaceutical industry to detect the presence of drug tablets in aluminum foil press-through packaging. However, the effect of X-rays on the pharmaceutical quality of drug tablets is not well known.

OBJECTIVE

In this study, the effect of X-rays on the pharmaceutical quality of drug tablets was investigated.

METHODS

Exposure of acetaminophen, loxoprofen and mefenamic acid tablets to X-ray doses of 0.34 mGy (thrice the dose by X-ray scanning) to 300 Gy (maximum dose from our X-ray equipment) was demonstrated, and the samples were evaluated by formulation tests.

RESULTS

Exposure to X-rays did not affect the pharmaceutical quality of the drug content. The samples exposed to X-rays exhibited almost the same profile in formulation tests (dissolution test, disintegrating test and hardness test) as control samples (0 Gy). The combination of X-ray exposure with accelerated temperature and humidity tests (six months) also did not affect the pharmaceutical quality. The color change of light-sensitive drugs (nifedipine and furosemide tablets) after X-ray exposure was negligible (< 1.0). In contrast, tablet color was remarkably changed by light from a D65 lamp.

CONCLUSION

The X-ray scanning and X-ray exposure under our experimental conditions did not affect the pharmaceutical quality of drug tablets.

Trace elements as tumor biomarkers and prognostic factors in breast cancer: a study through energy dispersive x-ray fluorescence

Background

The application and better understanding of traditional and new breast tumor biomarkers and prognostic factors are increasing due to the fact that they are able to identify individuals at high risk of breast cancer, who may benefit from preventive interventions. Also, biomarkers can make possible for physicians to design an individualized treatment for each patient. Previous studies showed that trace elements (TEs) determined by X-Ray Fluorescence (XRF) techniques are found in significantly higher concentrations in neoplastic breast tissues (malignant and benign) when compared with normal tissues. The aim of this work was to evaluate the potential of TEs, determined by the use of the Energy Dispersive X-Ray Fluorescence (EDXRF) technique, as biomarkers and prognostic factors in breast cancer.

Methods

By using EDXRF, we determined Ca, Fe, Cu, and Zn trace elements concentrations in 106 samples of normal and breast cancer tissues. Cut-off values for each TE were determined through Receiver Operating Characteristic (ROC) analysis from the TEs distributions. These values were used to set the positive or negative expression. This expression was subsequently correlated with clinical prognostic factors through Fisher’s exact test and chi-square test. Kaplan Meier survival curves were also evaluated to assess the effect of the expression of TEs in the overall patient survival.

Results

Concentrations of TEs are higher in neoplastic tissues (malignant and benign) when compared with normal tissues. Results from ROC analysis showed that TEs can be considered a tumor biomarker because, after establishing a cut-off value, it was possible to classify different tissues as normal or neoplastic, as well as different types of cancer.

The expression of TEs was found statistically correlated with age and menstrual status. The survival curves estimated by the Kaplan-Meier method showed that patients with positive expression for Cu presented a poor overall survival (p < 0.001).

Conclusions

This study suggests that TEs expression has a great potential of application as a tumor biomarker, once it was revealed to be an effective tool to distinguish different types of breast tissues and to identify the difference between malignant and benign tumors. The expressions of all TEs were found statistically correlated with well-known prognostic factors for breast cancer. The element copper also showed statistical correlation with overall survival.