E.D. Greaves

Analysis of human blood serum and human brain samples by total reflection X-ray fluorescence spectrometry applying Compton peak standardization

Abstract The method of using the Compton peak as internal standard in total reflection X-ray fluorescence (TXRF) determination is established for trace element determination of Fe, Cu, Zn, Se and Pt in human serum and of Cu and Zn in homogenized brain samples. A new method of spectrometer sensitivity calibration using spiked matrices with known amounts of trace elements is tested against established methods of matrix matching as well as internal element addition. The analytical results with the proposed procedure are compared to a certified international standard and to values with Atomic Absorption Spectrometry (AAS) obtaining analytical results of comparable accuracy and precision. The method is adequate for routine clinical analysis as it has the advantages of requiring very small amounts of material and simple preparations, which avoids the chemical digestion stage.

Determination of calcium, potassium, manganese, iron, copper and zinc levels in representative samples of two onion cultivars using total reflection X-ray fluorescence and ultrasound extraction procedure ☆

Abstract The chemical characterization of onion cultivar samples is an important tool for the enhancement of their productivity due to the fact that chemical composition is closed related to the quality of the products. A new sample preparation procedure for elemental characterization is proposed, involving the acid extraction of the analytes from crude samples by means of an ultrasonic bath, avoiding the required digestion of samples in vegetable tissue analysis. The technique of total reflection X-ray fluorescence (TXRF) was successfully applied for the simultaneous determination of the elements Ca, K, Mn, Fe, Cu and Zn. The procedure was compared with the wet ashing and dry ashing procedures for all the elements using multivariate analysis and the Scheffe test. The technique of flame atomic absorption spectrometry (FAAS) was employed for comparison purposes and accuracy evaluation of the proposed analysis method. A good agreement between the two techniques was found when using the dry ashing and ultrasound leaching procedures. The levels of each element found for representative samples of two onion cultivars (Yellow Granex PRR 502 and 438 Granex) were also compared by the same method. Levels of K, Mn and Zn were significantly higher in the 438 Granex cultivar, while levels of Ca, Fe and Cu were significantly higher in the Yellow Granex PRR 502 cultivar.

Selenium, copper and zinc in seminal plasma of men with varicocele, relationship with seminal parameters.

Varicocele has been associated with decrease in seminal parameters. Selenium (Se), copper (Cu), and zinc (Zn) are trace elements essential for normal spermatogenesis of mammals and play a critical role as antioxidant defense system enzymes. Se, Cu, and Zn are associated with sperm quality in fertile and infertile men. However, there is little information about Se, Cu, and Zn concentrations in semen in patients with varicocele and its association with seminal parameters. The purpose of this study was to determine the concentrations of Se, Cu, and Zn in semen of patients with varicocele and the relationship with seminal parameters. Total Reflection X-Ray Fluorescence was used for the fist time in the seminal fluid analysis. The concentration of selenium in men with varicocele was smaller than the normozoospermic group, while no differences were observed for both concentrations of zinc and copper. A significant positive correlation between zinc and selenium concentration was observed. Selenium in seminal plasma correlates with a good spermatozoa concentrations, motility, and morphology. Additionally, a significant positive correlation was observed between zinc levels and sperm count. In conclusion, a decrease in selenium concentration was associated with detriment of seminal parameters. A study should be conducted to evaluate the benefits of both zinc and selenium supplementation to improve seminal parameters in patients with varicocele.

Determination of copper, iron and zinc in spirituous beverages by total reflection X-ray fluorescence spectrometry ☆

Abstract The concentration of copper in traditional homemade alcoholic distillates produced in Venezuela (Cocuy de Penca) were determined by total reflection X-ray fluorescence (TXRF) using vanadium as internal standard. The results were compared to those obtained by flame atomic absorption spectrometry (FAAS). Three preparative methods of addition of vanadium were compared: classical internal standard addition, ‘layer on layer’ internal standard addition and in situ addition of internal standard. The TXRF procedures were accurate and the precision was comparable to that obtained by the FAAS technique. Copper levels were above the maximum allowed limits for similar beverages. Zinc and iron in commercial and homemade distilled beverages were also analyzed by TXRF with in situ addition of internal standard demonstrating the usefulness of this technique for trace metal determination in distillates.

Gross Alpha Radioactivity of Drinking Water in Venezuela

Bottled mineral water is consumed by a large population in Venezuela. The alpha emitters concentration was measured in samples of bottled water and water springs collected near the surface. Approximately 30% of the total mineral water suppliers was monitored. A database on natural and arttficial radioactivity in drinking water was produced. Results indicate that 54% of the waters sampled contain a total alpha radioactivity of less than 0.185 Bql-’ and only 12% above 0.37 Bq 1-t. Our results revealed a total annual dose of 2.3 mSv year-‘. 0 1997 Elsevier Science Limited. All rights reserved

Data processing technique for mercury determination by total-reflection X-ray fluorescence, using amalgamation with gold

We have developed a method to determine mercury concentrations using total-reflection X-ray fluorescence (TXRF) which leads to reliable results. The usual sample preparation procedure of TXRF is not applicable due to element loss by evaporation on account of its high vapor pressure. The method we developed consists of forming an amalgam on a thin layer of gold affixed in a specular-surface quartz reflector while it is in contact with a mercury ionic solution. Subsequently, a traditional TXRF analysis is performed. Since the mercury and gold peaks overlap, we have developed a data processing scheme to achieve the most precise results. Using a molybdenum anode X-ray tube at 40 kV and 20 mA, the limit of detection achieved for a 10-μl specimen with 2000 s counting time is 250 ppb.

Determination of Zn/Cu ratio and oligoelements in serum samples by total reflection X-ray fluorescence spectrometry for cancer diagnosis ☆

Abstract The method of quantification using the Compton peak as an internal standard, developed in a previous work, was applied to the routine determination of Fe, Cu, Zn and Se in serum samples from normal individuals and cancer patients by total reflection X-ray fluorescence spectrometry. Samples were classified according to age and sex of the donor, in order to determine reference values for normal individuals. Results indicate that the Zn/Cu ratio and the Cu concentration could prove to be useful tools for cancer diagnosis. Significant differences in these parameters between the normal and cancer group were found for all age ranges. The multielemental character of the technique, coupled with the small amounts of sample required and the short analysis time make it a valuable tool in clinical analysis.

SAX, software for the analysis of x‐ray fluorescence spectra

A program for chemical analysis by energy-dispersive x-ray spectrometry is described. Fluorescent multiplets are fitted to a high degree of accuracy by a method using an empirical energy-dependent peak-shape function derived from the spectrometer response to well resolved standard sample spectra. Elemental identification is accomplished via an interactive peak search and a complete K and L x-ray line library. Matrix correction routines for element quantification are provided for infinitely thick samples with fundamental parameters, including Compton correction, for thin samples and total reflection (TXRF) geometry and for semi-transparent light matrix pellets (emission-transmission method).

Trace element determination of mercury by total-reflection X-ray fluorescence

A rapid and simple method is presented for the determination of trace amounts of ionic mercury in solutions by total-reflection X-ray fluorescence. The method relies on the formation of a mercury amalgam on a 50 nm thick silver coating deposited on a specular-surface quartz reflector. Quantification of Hg in dilute HNO3 solutions is achieved, with a straight calibration line in the concentration range 50–350 ng ml−1. With excitation by a molybdenum anode X-ray tube at 40 kV and 20 mA, the limit of detection achieved for a 2 cm3 specimen with 1000 s counting time is 15 ng ml−1.

Comparison between proton-induced X-ray emission (PIXE) and total reflection X-ray fluorescence (TXRF) spectrometry for the elemental analysis of human amniotic fluid

A comparison between use of proton-induced x-ray emission (PIXE) and total reflection x-ray fluorescence (TXRF) techniques in relation to the elemental analysis of amniotic fluid (AF) was carried out by measuring the concentrations of Cl, K, Ca, Fe, Cu, Zn and Br. For 10 AF samples analyzed, the agreement between PIXE and a TXRF measurements was 100% for K, 60% for Cl and Ca, 80% for Fe and 50% for Cu. For Zn, although there was only a 20% agreement, the measured concentrations ranged between 0.1 and 1 μg/ml with a TXRF standard deviation as high as 0.070 μg/ml. For Br, a factor of 1.8±0.2 was obtained between TXRF and PIXE measurements, suggesting a systematic error between experiments. This work indicates that further investigation is required to determine the experimental conditions, e.g. sample preparation and irradiation, which lead to complete agreement between TXRF and PIXE when a complicated organic sample such as amniotic fluid is analyzed. Copyright