Total Reflection X-Ray Fluorescence (TXRF) is a mature technique to evaluate quantitatively the elemental composition of liquid samples deposited on clean and well polished reflectors. In this paper ...the results of the first worldwide TXRF round-robin test of water samples, involving 18 laboratories in 10 countries are presented and discussed. The test was performed within the framework of the VAMAS project, interlaboratory comparison of TXRF spectroscopy for environmental analysis, whose aim is to develop guidelines and a standard methodology for biological and environmental analysis by means of the TXRF analytical technique.
•The discussion of the first worldwide TXRF round-robin test of water samples (18 laboratories of 10 countries) is reported.•Drinking, waste, and desalinated water samples were tested.•Data dispersion sources were identified: sample concentration, preparation, fitting procedure, and quantification.•The protocol for TXRF analysis of drinking water is proposed.
Selenium is essential for many aspects of human health and, thus, the object of intensive medical research. This demands the use of analytical techniques capable of analysing selenium at low ...concentrations with high accuracy in widespread matrices and sometimes smallest sample amounts.
In connection with the increasing importance of selenium, there is a need for rapid and simple on-site (or near-to-site) selenium analysis in food basics like wheat at processing and production sites, as well as for the analysis of this element in dietary supplements. Common analytical techniques like electrothermal atomic absorption spectroscopy (ETAAS) and inductively-coupled plasma mass spectrometry (ICP-MS) are capable of analysing selenium in medical samples with detection limits in the range from 0.02 to 0.7
μg/l. Since in many cases less complicated and expensive analytical techniques are required, TXRF has been tested regarding its suitability for selenium analysis in different medical, food basics and dietary supplement samples applying most simple sample preparation techniques.
The reported results indicate that the accurate analysis of selenium in all sample types is possible. The detection limits of TXRF are in the range from 7 to 12
μg/l for medical samples and 0.1 to 0.2
mg/kg for food basics and dietary supplements. Although this sensitivity is low compared to established techniques, it is sufficient for the physiological concentrations of selenium in the investigated samples.
Abstract
Exposure to toxic metals and metalloids is a significant public health concern and can seriously affect human health. The aim of this study was to establish the presence of toxic metals and ...metalloids in the urine of non‐professional sportsmen who participated in a mountain ultramarathon using a benchtop total reflection x‐ray fluorescence (TXRF) system. TXRF allows for easy and rapid sample preparation and is therefore a potential candidate for simple and cost‐effective analysis. In this work, the TXRF‐Mo system was used for multielement analysis of the urine samples of 21 non‐professional athletes who ran a 53 km mountain ultra‐marathon. Urine samples were collected at four time points, at the beginning of the race (pre‐race samples), immediately, and 12 and 24 h post‐race. Al, As, Ba, Ni, Pb, Rb, Sr, V, and Tl were detected in the collected urine samples. The accuracy and precision of the proposed methods were verified by the analysis of reference materials (Seronorm™ Trace Elements Urine Level 2). The TXRF results were in agreement with the reference values and no significant differences were observed at the 95% confidence level. The detection limits for the elements of interest were also reasonable considering their concentration ranges in real samples. Changes were observed over time with increasing average urinary metals and metalloids levels, but only two significant results, were an increase in As and Rb. The results indicate a high degree of inter‐subject variability. The results obtained show that the content of toxic metals and metalloids increases in the urine samples collected after the race, which could confirm the statement that physical activity can increase the excretion of toxic metals and metalloids from the body. The simplicity of the TXRF method as well as its fast performance make it suitable for routine analysis.
Daily nutrition varies considerably among individuals. The number of vegetarians is increasing continuously due to ethical, environmental, religious or other reasons. There is growing concern over ...their nutritional status with respect to micronutrient deficiencies. Among the essential trace elements, Se is of prime importance as it is part of the active site in selenoproteins. European soil and plants are relatively poor sources of Se, while farm animals are generally supplemented with Se in order to improve their health and avoid deficiency syndromes. We therefore wondered whether German vegetarians display a measurable Se deficiency. To this end, we compared young vegetarians (n 54) and omnivores (n 53). We assessed their Se status by measuring extracellular glutathione peroxidase 3 (GPX3) activity, and concentrations of total serum Se and circulating Se-transport protein selenoprotein P (SEPP). GPX3 activities were not different between the groups, whereas both total Se and SEPP concentrations were reduced to 79·5 and 71·2 % in vegetarians compared with omnivores. When splitting the group of vegetarians into vegans (n 26) and vegetarians consuming egg and milk products (n 28), analyses of the Se-dependent biomarkers did not reveal significant differences. We conclude that low serum Se is mirrored by circulating SEPP concentrations, but not by GPX3 activities in marginally supplied individuals. The specific dietary Se sources, divergent metabolic routes of selenomethionine v. selenocysteine and the different saturation kinetics of GPX3 and SEPP probably underlie our contradictory findings. Whether German vegetarians and vegans need to be considered as a Se-deficient group depends on the biomarker chosen.
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