A.G. Karydas

Determination of uranium in human urine by total reflection X-ray fluorescence

Abstract Uranium has been classified as a toxic chemical. It affects the kidneys, with nephritis being the primarily chemically-induced effect in animals and humans. Intermediate-term studies on animals indicate that increased uranium doses are positively correlated with various biochemical effects and histopathological changes. Since the kidneys efficiently excrete in urine the major portion of solubilized uranium circulating in blood, an increased urinary uranium excretion can provide a sensitive quantitative measure of exposure, especially in the case of acute exposure. In the present work a method was developed for the quantitative determination of uranium in human urine. It combines the chemical treatment of urine, which results in a significant pre-concentration of uranium, with its subsequent detection by means of total reflection X-ray fluorescence (TXRF). The method has been proven to be relatively fast, offering detection limits that allow for monitoring uranium intake above normal levels.

Applicability of direct total reflection X-ray fluorescence analysis in the case of human blood serum samples☆

Abstract Total Reflection X-Ray Fluorescence (TXRF) is a well-established method, mainly applied in the analysis of liquid samples, offering very low detection limits in most of the cases. Direct application of the TXRF method is not so efficient in blood serum analysis, since the high content of the organic matrix increases significantly the background due to Compton scattering. Chemical treatment of the blood serum samples and related preconcentration techniques have been suggested in the literature, but they are time consuming and increase the possibility of adding contaminants in the sample. In this paper, the applicability of direct TXRF analysis in blood serum samples is examined. The insertion of a Mo filter, after the cut-off reflector, has been found to improve significantly the peak-to-background ratio, especially for the elements of interest such as Cu, Zn, Se and Br. The influence of self-absorption phenomena in the quantification procedure was also investigated with respect to the internal standard used and the sample mass analyzed. Precision and accuracy in the analysis was found to be approximately 4% over the whole atomic number range.

Chemical state speciation by resonant Raman scattering

In the resonant Raman scattering (RRS) process the emitted photon exhibits a continuous energy distribution with a high energy cutoff limit. This cutoff energy depends on the chemical state of the element under examination. In the present work, the possibility of identifying the chemical state of V atoms by employing RRS spectroscopy with a semiconductor Si(Li) detector is investigated. A proton induced Cr Kα x-ray beam was used as the incident radiation, having a fixed energy lower than the V K-absorption edge. The net RRS distributions extracted from the energy dispersive spectra of metallic V and its compound targets were simulated by an appropriate theoretical model. The results showed the possibility of employing RRS spectroscopy with a semiconductor detector for chemical speciation studies.

Fluorine determination in human healthy and carious teeth using the PIGE technique

Abstract The purpose of this study is to determine and compare the fluorine concentration in human teeth from two different populations, living in the Portuguese quite isolated islands of Acores: S. Miguel and Terceira. Both populations have similar dietary habits, similar occupational activities, mostly rural, and the age of both populations is more or less the same, around 40 years. No chronic diseases were registered in any of the donors. The two groups are exposed to different levels of fluorine in drinking water. Terceira island has moderate fluorine concentration levels (1–2 μg g−1) while S. Miguel island is known for the high fluorine concentration levels in its water (>3 μg g −1 ), especially in one area known as Furnas. Thirty-three teeth, 17 healthy and 16 carious without restoration (14 incisors and canines, 7 premolars and 12 molars), were collected and analyzed for the determination of fluorine concentration in the dentine region, using the nuclear reaction 19 F ( p , αγ ) 16 O . The teeth were cross-sectioned along the vertical plane and polished, in order to obtain a smooth and plane surface of about 1 mm thickness. In this work an association between caries prevalence and fluorine content of drinking water is discussed and the variation of fluorine concentration among different types of teeth (canines and incisors, premolars, molars) and physical state (carious and non-carious) is examined.

Importance of in-situ EDXRF Measurements in the Preservation and Conservation of Material Culture

The paper presents a series of in-situ Energy Dispersive X-ray Fluorescence (EDXRF) measurements performed in Greece and Cyprus for the characterization and quantitative analysis of valuable archaeological and historical artifacts, such as pigments on wall paintings and ceramics as well as gold and bronze alloys on sculpture and jewelry. The various types of instrumentation and analytical procedures used for the quantification of in-situ XRF data will be discussed. The experience acquired from the above investigations will be critically reviewed in order to assess the importance, as well as the limitations of in-situ EDXRF analyses in the preservation and conservation of our cultural heritage.

Proton induced monochromatic X-ray beams: A versatile source for resonant Raman scattering studies

Resonant raman scattering (RRS) can contribute considerably, under specific experimental conditions, to the attenuation of X-rays in matter. The experimental study of the RRS can lead to a better assessment of this contribution. In this work low energy proton induced vanadium Kα X-rays have been utilized in two different X-ray production geometries for RRS studies. The KL-RRS cross-sections for titanium and vanadium and the LM-RRS for cesium and barium are measured respectively, while the importance of the technique in the systematic measurement of X-ray interaction cross-sections in matter is also discussed.

A systematic study of proton capture reactions in the SeSb region at energies relevant to the p process

Abstract A systematic investigation of (p,γ) cross sections of nuclei from Se to Sb is presented. In-beam cross section measurements were carried out at E p = 1.4–5 MeV by using an array of 4 HPGe detectors of 100% relative efficiency shielded with BGO crystals. The S factors obtained are compared with the predictions of the statistical model code MOST.