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Trace elements are essential for life and their concentration in cells and tissues must be tightly maintained and controlled to avoid pathological conditions. Established methods to measure the concentration of trace elements in biological matrices often provide only single element information, are time-consuming, and require special sample preparation. Therefore, the development of straightforward and rapid analytical methods for enhanced, multi-trace element determination in biological samples is an important and raising field of trace element analysis. Herein, we report on the development and validation of a reliable method based on total reflection X-ray fluorescence (TXRF) analysis to precisely quantify iron and other trace metals in a variety of biological samples, such as the liver, parenchymal and non-parenchymal liver cells, and bone marrow–derived macrophages. We show that TXRF allows fast and simple one-point calibration by addition of an internal standard and has the potential of multi-element analysis in minute sample amounts. The method was validated for iron by recovery experiments in homogenates in a wide concentration range from 1 to 1600 μg/L applying well-established graphite furnace atomic absorption spectrometry (GFAAS) as a reference method. The recovery rate of 99.93 ± 0.14% reveals the absence of systematic errors. Furthermore, the standard reference material “bovine liver” (SRM 1577c, NIST) was investigated in order to validate the method for further biometals. Quantitative recoveries (92–106%) of copper, iron, zinc, and manganese prove the suitability of the developed method. The limits of detection for the minute sample amounts are in the low picogram range.

Trace elements are essential for the human body’s various physiological processes but if they are present in higher concentration, these elements turn to be toxic and cause adverse effect on physiological processes. Similarly, deficiency of these essential elements also affects physiological processes and leads to abnormal metabolic activities. There is a lot of interest in recent years to know the mystery behind the involvement of trace elements in the metabolic activities of autistic children suspecting that it may be a risk factor in the aetiology of autism. The present study aims to analyse the plasma trace elements in autistic children using the total reflection X-ray fluorescence (TXRF) technique. Plasma samples from 70 autistic children (mean age: 11.5 ± 3.1) were analysed with 70 age- and sex-matched healthy children as controls (mean age: 12 ± 2.5). TXRF analysis revealed the higher concentration of copper (1227.8 ± 17.8), chromium (7.1 ± 2.5), bromine (2695.1 ± 24) and arsenic (126.3 ± 10) and lower concentration of potassium (440.1 ± 25), iron (1039.6 ± 28), zinc (635.7 ± 21), selenium (52.3 ± 8.5), rubidium (1528.9 ± 28) and molybdenum (162,800.8 ± 14) elements in the plasma of autistic children in comparison to healthy controls. Findings of the first study from India suggest these altered concentrations in elements in autistic children over normal healthy children affect the physiological processes and metabolism. Further studies are needed to clarify the association between the altered element concentration and physiology of autism in the North Karnataka population in India.

We have developed an approach for joint determination of La, Fe, and Sr in solutions and suspensions of (La,Sr)FeO 3 composites by total reflection X-ray fluorescence (TXRF) spectroscopy with the aim of assessing the effect of strontium substitution for lanthanum on the gas-sensing properties of lanthanum ferrites. A gallium solution with a concentration of 50 mg/L was used as an internal standard for determination of the constituent elements. The adequacy of the results obtained was ascertained using inductively coupled plasma atomic emission spectroscopy (ICP AES) of solutions of the samples. According to the data we obtained, there were no interelement effects when La, Fe, and Sr were present together in solution. The reproducibility of the TXRF determination results ( S r ) was 0.04, 0.05, and 0.06 for La, Fe, and Sr, respectively. The reproducibility of the results for the suspensions was due to the small particle size (15–17 nm) and the uniform distribution of the internal standard in the aliquot in the sample preparation procedure chosen. All of the materials were shown to consist of a single phase, corresponding to pure lanthanum ferrite with an orthorhombic crystal lattice (ICDD card no. 37-1493). The absence of unindexed reflections in their X-ray diffraction patterns points to successful incorporation of Sr 2+ cations into the La 3+ site. Doping of lanthanum ferrite with strontium was shown to improve the sensitivity of the materials to CO, NH 3 , methanol, and acetone and reduce the optimal working temperature of the sensor by 50–150°C. The best gas-sensing properties were offered by the lanthanum ferrite nanofiber containing the lowest Sr concentration (0.01 at %). At the same time, the insensitivity of the materials to methane and benzene is the result of the higher stability of their molecules to acid–base active surface centers of La 1– x Me x FeO 3 .

This work aimed to evaluate the salivary concentration of chemical elements in patients undergoing orthodontic treatment with fixed orthodontic appliances and removable aligners. Twelve Angle Class I and II orthodontic patients undergoing treatment with conventional fixed appliances and 15 patients treated with removable aligners provided unstimulated whole saliva samples before treatment (pre) and after 3 months of treatment (post). The concentration and secretion rate of chemical elements in saliva were determined by total reflection X-ray fluorescence. Differences from pre to post and between groups were determined with the paired T test or Wilcoxon test, and two-way ANOVA, considering P < 0.05. The concentrations of S, Cl, and K decreased, while Zn increased significantly (P < 0.05) between pre and post treatment with the fixed appliance treatment. The salivary secretion rate of S was decreased from pre to post in the fixed appliance group. No differences in the concentration and secretion rate of chemical elements were detected from pre to post in the Invisalign group. Fe secretion rate presented an interaction between time and treatment, with lower secretion at post (P = 0.02) in the Invisalign group. Increased Br secretion rate and decreased Rb, Fe, P, and K in Invisalign patients suggested a better salivary electrolyte profile regarding periodontal bone remodeling. No significant alterations in ions associated with metal corrosion and inflammatory reactions were detected in orthodontic patients under dental plaque control.

An approach to determining the composition of new biocompatible materials based on cerium-containing calcium phosphates using the TXRF method is proposed. The ranges of analyte contents in solutions were determined for the correct determination of Ca, P, and Ce using the external reference method. A systematic underestimation of the calcium signal was noted when its content in the analyzed composite sample was above 30 mg/L. In order to assess the compliance of the sample with the thin layer criterion, an analysis of the Compton scattering spectra for the ceramic sample solution was carried out; the maximum value was 16.8 keV (96°). According to the plot of the mass attenuation coefficient for a film of a given composition, the attenuation of the intensity of the calcium line perpendicular to the substrate is not associated with absorption of the sample. Internal reference samples (Gd and Cu) were selected and conditions were found for determining micro- and macrocomponents in solutions and suspensions of samples. It has been shown that, when the calcium content in the sample is up to 50 mg/L, it is possible to correctly determine Ca, P, and Ce using the TXRF method in solutions and suspensions with S r of 0.05 and 0.09, respectively. The convergence of the results obtained using the external and internal reference methods with appropriate dilutions of solutions and suspensions was noted.

The experimental electron density distributions in two coordination compounds – one with a central Cu(I) atom and the other with Cu(II), coordinated by the same biphenyldiimino dithioether ( bite ) type of ligand – have been obtained from high-resolution X-ray reflection data to model the possible electron predisposition for the redox reaction in blue copper proteins. The bite ligand has been adapted to the conformation required by the central atom.

AbstractThe crush-leach technique is a frequently used method to determine the bulk composition of fluid inclusions trapped in a range of geological samples. We present a modified crush-leach technique combining ion chromatography (IC) and total reflection X-ray fluorescence spectroscopy (TXRF) which allows to determine a range of major, minor and trace elements out of one leachate. To date, trace element detection by means of TXRF is barely used in geosciences, although it combines the advantages of low to very low detection limits (µg/L to ng/L range), small sample amount needed (µL-range) and a fast and inexpensive analytical procedure. Previously described problems of adsorption of polyvalent cations at sample surfaces have been overcome by using acidified water as a leachate. Instead, it has been demonstrated that, for example, the syringe filter type used for IC measurements influences contamination and/or adsorption for a number of elements. The proposed method combination was evaluated for accuracy, reproducibility and system blanks and subsequently applied to quartz samples from hydrothermal vein deposits of the Schwarzwald ore district, SW Germany.

An approach to TXRF determination of the composition of perovskite nanocomposites of the putative compositions CsPbBr 2 Cl and CsPbBr 2 I is proposed. Sample preparation consists in the treatment of hydrophobic samples with dimethylformamide (DMFA) and the subsequent dilution of the obtained solutions with water. When using a copper solution as an internal standard, the reproducibility of the results of TXRF determination of the elements is attained with S r no more than 0.05. The validity of the determination of Cs, Pb, Br, and I is confirmed by the results of their determination by ICP-MS in solutions after processing samples in DMFA followed by dilution with 2% HNO 3 for Cs, Pb, and Br or tetramethylammonium hydroxide (TMAH) for Cs, Pb, Br, and I, whereas the determination of chlorides is confirmed by the method of direct potentiometry in diluted solutions. It is shown that lead does not form insoluble chlorides in the TMAH solution and does not interfere with the determination. The effect of bromides on the determination of chlorides is characterized by a potentiometric coefficient of 10 –3 . The results obtained provide the determination of the stoichiometry of the synthesized compounds CsPbBr 2 Cl and CsPbBr 2.7 I 0.3 .

An approach to the simultaneous isolation of As(III) and Se(IV) from solutions on a new S,N-containing sorbent followed by determination of the analyte in the sorbent phase by total reflection X-ray fluorescence (TXRF) is proposed. To match the goal, a sorbent with a branched structure is synthesized on the basis of polyacrylamide modified with formaldehyde and hydrogen sulfide. This is a heteroatomic copolymer containing sulfide bridges and crosslinking by a tertiary amine in its chain. Conditions for the quantitative coextraction of As(III) and Se(IV), namely, sorption in 1 M solutions of HNO 3 in the presence of calcium ions, heating up to 60°C, and phase contact time of 1 h, are determined. The mechanism of sorption interaction of the analytes under specified conditions is discussed. It is found that 100-fold excesses of iron, zinc, and copper do not interfere with the extraction of the analytes; therefore, it is possible to apply the sorbent for the extraction of As(III) and Se(IV) from different types of raw materials and processed products. A procedure for the direct X-ray fluorescence quantification of arsenic and selenium with S r of 0.09 and 0.08, respectively, in the sorbent phase is developed. The correctness of the results is confirmed by ICP-MS upon the analysis of aqueous reference solutions after the dissolution of the sorbate in HNO 3 (1 : 1).

Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I1,1/I1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I1,1/I1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.