Pehuén (Araucaria araucana) seed residues are a valuable source of natural antioxidants with nutraceutical, chemoprotective and metal corrosion-inhibiting properties.

In the last decade, green chemistry has been attracting great interest in many contexts, including, among others, natural antioxidants. However, only a few works deal with natural residue extracts and biowaste, which could be an efficient, economical and environmentally friendly source for the production of useful compounds. In this study, we look for antioxidant activity in Araucaria araucana seeds, an iconic pine species of the Argentine and Chilean Patagonia commonly known as "pehuén". Piñones are the edible pehuén seeds, and it is estimated that approximately 40 tons of piñones are harvested annually in Argentina and Chile. The chemical composition, antioxidants, metal corrosion-inhibiting properties and biological activity of edible and discarded piñón tissues were determined. Acute toxicity was discarded by in vitro testing and double fluorescent staining. Biological activity was evaluated in vivo by determining redox markers in salivary glands from rats treated with Cyclophosphamide (an oncological drug). All piñón tissues had antioxidants and antioxidant activity, with the coats showing the highest levels (up to 404 µg ascorbic acid equivalent per mg). The coats, in particular, had high gallic acid, catechin, quercetin and tannin contents, and more antioxidant activity, polyphenols and flavonoids than berries from the region. Results by X-ray fluorescence spectrometry showed that Na, Mg, P, S, Cl, K, and Ca were majority elements in the coat, embryo and endosperm. Furthermore, coat extract also showed significant anti-corrosion activity and in vivo protection against oxidative damage. The results indicate that piñón biowaste is a low-cost attractive source of natural antioxidants with potential nutraceutical, medical and metal corrosion protection applications.

Simple and reliable determination of Zn and some additional elements in seminal plasma samples by using total reflection X-ray fluorescence spectroscopy.

Trace elements are essential for the normal spermatogenesis of mammals and play a critical role in sperm quality and pathological processes e.g. inflammation. Consequently, multi-elemental analysis of seminal plasma (SP) may provide significant information on physiological and pathophysiological processes occurring in the male reproductive tract. Therefore, the development of a simple, fast and reliable method for seminal plasma (SP) analysis by total reflection X-ray fluorescence spectrometry (TXRF) could be useful for both, scientific and clinical studies. In this study, a detailed assessment of the sample preparation parameters and measurement conditions, including analysis of the shape and element distribution of the deposited residue on the reflector by micro X-ray fluorescence spectrometry, was carried out. Using the best analytical conditions, limits of detection for trace elements were found to be in the range of 0.04-0.3 mg kg-1. Trueness and precision of the results, evaluated by spiked SP sample analysis, were in most cases acceptable with recovery values in the range of 87-109% and relative standard deviations 3-12% (n = 5). The developed TXRF method was applied for the analysis of several SP samples from patients with different diagnoses and the results were compared with those obtained by ICP-OES. Among the studied trace elements with a role in the antioxidant defence system only Zn could be quantified and some differences in Zn concentrations among studied groups were observed. However, further studies on a large number of samples are required to define the exact relationship between the element composition and semen quality.

Cellulose mini-membranes modified with TiO2 for separation, determination, and speciation of arsenates and selenites.

Sorptive and selective mini-membranes based on TiO2 directly synthesized onto cellulose filters (TiO2@cellulose) have been developed. The in situ synthesis of TiO2@cellulose applied is simple and economically advantageous. The obtained membranes can be useful for (1) separating arsenic(V) and selenium(IV) from other ions and organic matter, (2) speciation of arsenic and selenium, and (3) determining ulratraces of these ions in water samples. The membranes exhibit good stability and high maximum adsorption capacities for Se(IV) (71 mg g-1) and As(V) (41 mg g-1). A monolayer chemical adsorption of analytes on the membranes was confirmed. The structure of membranes was examined with scanning electron microscopy, x-ray diffractometry, and micro energy-dispersive x-ray fluorescence spectrometry (µ-EDXRF). The membranes were characterized by homogenous distribution of TiO2 onto cellulose. The TiO2@cellulose was used as a new sorbent in micro-solid phase extraction for determination of Se(IV) and As(V) by EDXRF. Using direct analysis of mini-membranes after sorption of analytes avoids the elution step. Thus, the proposed procedure is an attractive and solvent-free option for quantitative monitoring of Se(IV) and As(V) in different materials. Both analytes were quantitatively and simultaneously separated/determined from samples at pH 2 with very good recovery (close to 100%), precision (4.5%), and detection limits (0.4 ng mL-1 Se and 0.25 ng mL-1 As). TiO2@cellulose membranes were applied to water analysis. Graphical-abstract Effective method for determination of ultra trace arsenates and selenites using cellulose-based sorbent.

Determination of gold leaf thickness using X-ray fluorescence spectrometry: Accuracy comparison using analytical methodology and Monte Carlo simulations.

In this work, we compared the accuracy of gold leaves thickness determination using X-ray Fluorescence (XRF) setups for different X-ray excitation sources. The sources used consisted on: a) direct Bremsstrahlung from an Amptek Mini-X X-ray tube with Rh target, b) partially monochromatized radiation of the same X-ray tube using combination of Al and Ag filters and, c) monochromatic radiation using secondary target, in a portable setup with triaxial geometry. The performance of the used setups was compared using model samples made with gold foil standard reference materials of known thicknesses (1, 2 and 2.5 µm). Thickness determination was based on the selective attenuation that the different energies of a given element of an under-layer undergo in the gilded layer. Ideally, as it can be expected from physics fundamentals, monochromatic radiation is needed for improved accuracy. However, considering the difficulties in using monochromatic radiation in portable instrumentation applicable in Cultural Heritage studies, filtered radiation can also be used for reliable results. Moreover, Monte Carlo simulations of the portable setup with conventional planar geometry were performed for comparison and for future application in more complex samples.

Interaction of silver nanoparticles with mediterranean agricultural soils: Lab-controlled adsorption and desorption studies.

The production of silver nanoparticles (AgNPs) has increased tremendously during recent years due to their antibacterial and physicochemical properties. As a consequence, these particles are released inevitably into the environment, with soil being the main sink of disposal. Soil interactions have an effect on AgNP mobility, transport and bioavailability. To understand AgNP adsorption processes, lab-controlled kinetic studies were performed. Batch tests performed with five different Mediterranean agricultural soils showed that cation exchange capacity and electrical conductivity are the main parameters controlling the adsorption processes. The adsorption kinetics of different sized (40, 75, 100 and 200 nm) and coated (citrate, polyvinylpyrrolidone and polyethyleneglycol (PEG)) AgNPs indicated that these nanoparticle properties have also an effect on the adsorption processes. To assess the mobility and bioavailability of AgNPs and to determine if their form is maintained during adsorption/desorption processes, loaded soils were submitted to leaching tests three weeks after batch adsorption studies. The DIN 38414-S4 extraction method indicated that AgNPs were strongly retained on soils, and single-particle inductively coupled plasma mass spectrometry confirmed that silver particles maintained their nanoform, except for 100 nm PEG-AgNPs and 40 nm citrate-coated AgNPs. The DTPA (diethylenetriaminepentaacetic acid) leaching test was more effective in extracting silver, but there was no presence of AgNPs in almost all of these leachates.

Comprehensive analysis of renal arsenic accumulation using images based on X-ray fluorescence at the tissue, cellular, and subcellular levels.

Exposure to arsenic (As) through drinking water results in accumulation of As and its methylated metabolites in several organs, promoting adverse health effects, particularly potential development of cancer. Arsenic toxicity is a serious global health concern since over 200 million people are chronically exposed worldwide. Abundant biochemical and epidemiological evidence indicates that the kidney is an important site of uptake and accumulation of As, and mitochondrial damage plays a crucial role in arsenic toxicity. However, non-destructive analyses and in situ images revealing As fate in renal cells and tissue are scarce or almost non-existent. In this work, kidney tissue from exposed rats was analyzed by EDXRF (Energy dispersive X-ray fluorescence), micro-SRXRF (micro X-ray Fluorescence using Synchrotron Radiation), SRTXRF (SRXRF in total reflection condition), SEM-EDX (Scanning Electron Microscope in combination with EDXRF) and SRXRF-XANES (SRXRF in combination with X-ray Absorption Near Edge Spectroscopy). Our results provide evidence of renal cortex distribution of As with periglomerular localization, co-localization of S, Cu and As in subcellular compartment of proximal tubule cells, mono-methylarsonous acid accumulation in renal cortex mitochondria, and altered subcellular concentration and distribution of other elements.

Critical evaluation of the use of total reflection X-ray fluorescence spectrometry for the analysis of whole blood samples: application to patients with thyroid gland diseases.

Multielemental analysis of whole blood can provide significant information for the evaluation of nutritional status and diagnosis of certain diseases as well as for the assessment of exposure to potentially toxic metals. However, the quantification of multiple elements in whole blood is not easy partly because of the wide variation in element concentrations (from ng L-1 to g L-1) and the complex matrix. The aim of this work was to develop a fast, sustainable, and reliable analytical method, in combination with low-power TXRF, for multielemental analysis of blood samples. Firstly, a set of experiments were carried out to select the best diluent type and dilution factor using the control material SeronormTM Trace Elements Whole Blood L-1. A critical evaluation of the parameters affecting the sample deposition on the reflector was also carried out including a study of the shape and element distribution of the deposited residue on the reflector by micro X-ray fluorescence spectrometry. Using the best analytical conditions, limits of detection estimated were in the low milligrams per kilogram range and similar to those obtained using more complex sample treatments such as digestion. Accuracy and precision of the results were in most cases acceptable (recoveries 89-102%, RSD 6-8%, n = 5). Only underestimated values were obtained for light elements such as potassium. To prove the applicability of the method, several blood samples from control and thyroid disease patients were analyzed. Despite the fact that more samples need to be analyzed, it seems that Zn and Br contents in some of the patients are significantly higher compared to control samples. Graphical abstract.

Determination and speciation of ultratrace arsenic and chromium species using aluminium oxide supported on graphene oxide.

Alumina supported on graphene oxide (Al2O3/GO) nanocomposite as new nanosorbent in dispersive micro-solid phase extraction (DMSPE) for As(V) and Cr(III) preconcentration is described. The crucial issue of the study is synthesis of novel nanocomposite suitable for sorption of selected species of arsenic and chromium. Al2O3/GO demonstrates selectivity toward arsenates in the presence of arsenites at pH 5 and chromium(III) ions in the presence of chromate anions at pH 6. The Al2O3/GO nanocomposite was characterized by scanning electron microscopy (SEM) transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and the Raman spectroscopy. The maximum adsorption capacity calculated based on the Langmuir adsorption model were 43.9 mg g-1 and 53.9 mg g-1 for As(V) and Cr(III), respectively. The nanocomposite was used as solid sorbent in preconcentration of As(V) and Cr(III)_ions from water samples and their determination using energy dispersive X-ray fluorescence spectrometry (EDXRF). The As(V) and Cr(III) ions can be quantitatively preconcentrated from 25 to 100 mL aqueous samples within 5 min using DMSPE procedure and 1 mg of Al2O3/GO. The nanocomposite was also used for preparation of Al2O3/GO membrane. Then, As(V) and Cr(III)_ions can be retained under flow condition by passing analyzed solution through Al2O3/GO membrane. Under the optimized conditions, As(V) and Cr(III) ions can be determined with very good recovery (92-108%), precision (RSD 2.7-4.0%) and excellent limit of detection (0.02 ng mL-1 As and 0.11 ng mL-1 Cr). The accuracy of the method was studied by analyzing certified reference materials (NIST 1640a) and spiked real water samples.

Ceria nanoparticles deposited on graphene nanosheets for adsorption of copper(II) and lead(II) ions and of anionic species of arsenic and selenium.

A nanocomposite prepared from graphene nanosheets and cerium nanoparticles (G/CeO2) was applied to the extraction of Se(IV), As(V), As(III), Cu(II) and Pb(II). The structure of G/CeO2 was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The optimal pH values for extraction are 4.0 for As(V), 3.0 for Se(IV), and 6.0 for both Cu(II) and Pb(II). The maximum adsorption capacity of G/CeO2 (expressed as mg·g-1) were calculated by the Langmuir model and are found to be 8.4 for As(V), 14.1 for Se(IV), 50.0 for Cu(II) and 75.6 for Pb(II). The sorbent was applied to dispersive solid phase microextraction prior to direct quantitation by energy-dispersive X-ray fluorescence spectrometry without the need for prior elution. The limits of detection (in ng·mL-1 units) are 0.10 for As(V), 0.11 for Se(IV), 0.19 for Cu(II) and 0.21 for Pb(II). The precisions (RSDs) are <4.5%. The accuracy of the method (1 - 4%) was verified by analysis of the certified reference material (CRM 1640a - natural water). The method was successfully applied in ultratrace element determination and to the speciation of selenium in environmental waters. Graphical abstract The method gives possibility of simultaneous preconcentration and determination in environmental waters of both anionic (As(V) and Se(IV)) and cationic (Cu(II) and Pb(II)) forms of selected metals using graphene nanosheets and cerium nanoparticles. Se(IV) can be selective determined in the presence of Se(VI).

Usefulness of a Dual Macro- and Micro-Energy-Dispersive X-Ray Fluorescence Spectrometer to Develop Quantitative Methodologies for Historic Mortar and Related Materials Characterization.

Wavelength dispersive X-ray fluorescence (WD-XRF) spectrometry has been widely used for elemental quantification of mortars and cements. In this kind of instrument, samples are usually prepared as pellets or fused beads and the whole volume of sample is measured at once. In this work, the usefulness of a dual energy dispersive X-ray fluorescence spectrometer (ED-XRF), working at two lateral resolutions (1 mm and 25 µm) for macro and microanalysis respectively, to develop quantitative methods for the elemental characterization of mortars and concretes is demonstrated. A crucial step before developing any quantitative method with this kind of spectrometers is to verify the homogeneity of the standards at these two lateral resolutions. This new ED-XRF quantitative method also demonstrated the importance of matrix effects in the accuracy of the results being necessary to use Certified Reference Materials as standards. The results obtained with the ED-XRF quantitative method were compared with the ones obtained with two WD-XRF quantitative methods employing two different sample preparation strategies (pellets and fused beads). The selected ED-XRF and both WD-XRF quantitative methods were applied to the analysis of real mortars. The accuracy of the ED-XRF results turn out to be similar to the one achieved by WD-XRF, except for the lightest elements (Na and Mg). The results described in this work proved that µ-ED-XRF spectrometers can be used not only for acquiring high resolution elemental map distributions, but also to perform accurate quantitative studies avoiding the use of more sophisticated WD-XRF systems or the acid extraction/alkaline fusion required as destructive pretreatment in Inductively coupled plasma mass spectrometry based procedures.

Graphene Oxide Decorated with Cerium(IV) Oxide in Determination of Ultratrace Metal Ions and Speciation of Selenium.

Graphene oxide decorated with cerium(IV) oxide (GO/CeO2) was synthesized and applied in adsorption of several metal ions such as As(III), As(V), Se(IV), Cu(II), and Pb(II) from aqueous samples. The important feature of GO/CeO2 nanocomposite is also its selectivity toward selenite in the presence of selenate. The structure of GO/CeO2 has been proven by microscopic and spectroscopic techniques. The maximum adsorption capacities of GO/CeO2 calculated by Langmuir model toward arsenic, selenium, copper, and lead ions are between 6 and 30 mg g-1. An interesting feature of this adsorbent is its excellent dispersibility in water. Thus, GO/CeO2 nanocomposite is ideal for fast and simple determination of heavy metal ions using dispersive microsolid phase extraction (DMSPE). Moreover, coupling DMSPE with energy-dispersive X-ray fluorescence spectrometry (EDXRF) is extremely beneficial because it allows direct analysis of adsorbent. Thus, the analyte elution step, as needed in many analytical techniques, was obviated. The influence of sample volume and the sorption time as well as the influence of foreign ions and humic acid on the recovery of determined elements are discussed in the paper. The results showed that developed methodology provided low limits of detection (0.07-0.17 µg/L) and good precision (RSD < 4%). The GO/CeO2 nanocomposite was applied to analysis of real water samples and certified reference materials (CRM) groundwater (BCR-610) and pig kidney (ERM-BB186).

Holocene geochemical footprint from Semi-arid alpine wetlands in southern Spain.

Here we provide the geochemical dataset that our research group has collected after 10 years of investigation in the Sierra Nevada National Park in southern Spain. These data come from Holocene sedimentary records from four alpine sites (ranging from ∼2500 to ∼3000 masl): two peatlands and two shallow lakes. Different kinds of organic and inorganic analyses have been conducted. The organic matter in the bulk sediment was characterised using elemental measurements and isotope-ratio mass spectrometry (EA-IRMS). Leaf waxes in the sediment were investigated by means of chromatography with flame-ionization detection and mass spectrometry (GC-FID, GC-MS). Major, minor and trace elements of the sediments were analysed with atomic absorption (AAS), inductively coupled plasma mass spectrometry (ICP-MS), as well as X-ray scanning fluorescence. These data can be reused by environmental researchers and soil and land managers of the Sierra Nevada National Park and similar regions to identify the effect of natural climate change, overprinted by human impact, as well as to project new management policies in similar protected areas.

Alpine bogs of southern Spain show human-induced environmental change superimposed on long-term natural variations.

Recent studies have proved that high elevation environments, especially remote wetlands, are exceptional ecological sensors of global change. For example, European glaciers have retreated during the 20th century while the Sierra Nevada National Park in southern Spain witnessed the first complete disappearance of modern glaciers in Europe. Given that the effects of climatic fluctuations on local ecosystems are complex in these sensitive alpine areas, it is crucial to identify their long-term natural trends, ecological thresholds, and responses to human impact. In this study, the geochemical records from two adjacent alpine bogs in the protected Sierra Nevada National Park reveal different sensitivities and long-term environmental responses, despite similar natural forcings, such as solar radiation and the North Atlantic Oscillation, during the late Holocene. After the Industrial Revolution both bogs registered an independent, abrupt and enhanced response to the anthropogenic forcing, at the same time that the last glaciers disappeared. The different response recorded at each site suggests that the National Park and land managers of similar regions need to consider landscape and environmental evolution in addition to changing climate to fully understand implications of climate and human influence.

Atmospheric dust deposition on soils around an abandoned fluorite mine (Hammam Zriba, NE Tunisia).

The present study focuses on the eolian dispersion and dust deposition, of major and trace elements in soils in a semi-arid climate, around an old fluorite (CaF2) and barite (BaSO4) mine, located in Hammam Zriba in Northern Tunisia. Ore deposits from this site contain a high amount of metal sulphides constituting heavy metal pollution in the surrounding environment. Samples of waste from the surface of mine tailings and agricultural topsoil samples in the vicinity of the mine were collected. The soil samples and a control sample from unpolluted area, were taken in the direction of prevailing northwest and west winds. Chemical analysis of these solids was performed using both X-ray fluorescence and X-ray diffraction. To determine the transfer from mine wastes to the soils, soluble fraction was performed by inductively coupled plasma and ionic chromatography. The fine grained size fraction of the un-restored tailings, still contained significant levels of barium, strontium, sulphur, fluorine, zinc and lead with mean percentages (wt%) of 30 (calculated as BaO), 13 (as SrO), 10 (as SO3), 4 (F), 2 (Zn) and 1.2 (Pb). Also, high concentrations of cadmium (Cd), arsenic (As) and mercury (Hg) were found with an averages of 36, 24 and 1.2mgkg-1, respectively. As a result of the eolian erosion of the tailings and their subsequent wind transport, the concentrations of Ba, Sr, S, F, Zn and Pb were extremely high in the soils near to the tailings dumps, with 5%, 4%, 7%, 1%, 0.8% and 0.2%, respectively. Concentration of major pollutants decreases with distance, but they were high even in the farthest samples. Same spatial distribution was observed for Cd, As and Hg. While, the other elements follow different spatial patterns. The leaching test revealed that most elements in the mining wastes, except for the anions, had a low solubility despite their high bulk concentrations. According the 2003/33/CE Decision Threshold, some of these tailings samples were considered as hazardous. Furthermore, other waste samples, considered non hazardous, were not inert. In contrast, the SO42-, Ba, Pb and Sb leachable contents measured in most of the soil samples were relatively high, exceeding the inert threshold for landfill disposal of wastes.

Development of X-ray Fluorescence Quantitative Methodologies To Analyze Aqueous and Acid Extracts from Building Materials Belonging to Cultural Heritage.

Energy dispersive X-ray fluorescence spectrometry (ED-XRF) is widely used in art and cultural heritage for direct measurements and elemental quantification of solid samples. However, in the literature there are not works dealing with the quantitative application of ED-XRF to liquid extracts coming from samples belonging to cultural heritage. In this work, a novel methodology based on the use of ED-XRF spectrometry after thin film deposition on special sample retainers and a subsequent evaporation was developed to quantify light elements (Z ≤ 20) in aqueous extracts and heavy elements (Z > 20) in acid extracts, coming from materials and degradation products belonging to built heritage (mortars, black crusts, and calcium carbonate formations). For this purpose, special sample retainers were used instead of more common adsorbent filter papers. Three different ED-XRF calibration methodologies were designed as elemental quantification tools and "green chemistry" alternatives to conventional techniques. On the one hand, the developed external ED-XRF calibration methodology for elements with Z ≤ 20 was proposed as an alternative to ion chromatography to obtain information about the degradation processes that the building materials suffered. On the other hand, the external ED-XRF calibration for elements with Z > 20 in acid extracts was optimized as a faster and cleaner quantification alternative to inductively coupled plasma mass spectrometry (ICPMS). Finally, with the aim to reduce the matrix effect and to improve the quantitative results for elements with Z > 20 in acid extracts, a novel ED-XRF calibration methodology based on standard additions was successfully designed and applied to real samples belonging to built heritage.

Immunotoxicological effects of arsenic bioaccumulation on spatial metallomics and cellular enzyme response in the spleen of male Wistar rats after oral intake.

Arsenic (As) is a worldwide environmental contaminant, which compromises immunity and causes various associated disorders. To further investigate its immunotoxicity, male Wistar rats were exposed to 100ppm of sodium arsenite (inorganic AsIII) in drinking water for 2 months. Given that metals are significant immune regulators, their content and distribution were analysed in spleen tissues, to then evaluate subsequent changes of redox enzyme responses in spleen parenchyma cells (splenocytes). X-ray fluorescence spectrometry demonstrated As accumulation in both white and red pulps (p<0.005), and As-related pulp-dependent modifications of the content of Cu, Ca, Zn and Fe (p<0.01). Correlational path analysis revealed direct effects of As on their spatial distribution (Cu: -0.76, Ca: -0.61, Zn: 0.38; p<0.02). As-exposed splenocytes showed ɣ-glutamyltranspeptidase inhibition, peroxidase induction, and variable responses of nitric oxide synthase (p<0.05). Concanavalin A-treated splenocytes (T cell mitogen) were more susceptible in vitro to these As-related enzymatic changes than those treated with lipopolysaccharide (B cell mitogen) (p<0.05). The study thus established the impact of As bioaccumulation on metallic spatial homeostasis in the spleen, and then identified enzymatic dysfunctions in splenocytes. This suggested that arsenic disrupts biometal-dependent immune pathways and redox homeostasis, with mitogen exposure modifying the toxicological response.

Bromine and bromide content in soils: Analytical approach from total reflection X-ray fluorescence spectrometry.

Monitoring total bromine and bromide concentrations in soils is significant in many environmental studies. Thus fast analytical methodologies that entail simple sample preparation and low-cost analyses are desired. In the present work, the possibilities and drawbacks of low-power total reflection X-ray fluorescence spectrometry (TXRF) for the determination of total bromine and bromide contents in soils were evaluated. The direct analysis of a solid suspension using 20 mg of fine ground soil (<63 µm) gave a 3.7 mg kg(-1) limit of detection for bromine which, in most cases, was suitable for monitoring total bromine content in soils (Br content range in soils = 5-40 mg kg(-1)). Information about bromide determination in soils is also possible by analyzing the Br content in water soil extracts. In this case, the TXRF analysis can be directly performed by depositing 10 µL of the internal standardized soil extract sample on a quartz glass reflector in a measuring time of 1500 s. The bromide limit of detection by this approach was 10 µg L(-1). Good agreement was obtained between the TXRF results for the total bromine and bromide determinations in soils and those obtained by other popular analytical techniques, e.g. energy dispersive X-ray fluorescence spectrometry (total bromine) and ionic chromatography (bromide). As a study case, the TXRF method was applied to study bromine accumulation in two agricultural soils fumigated with a methyl bromide pesticide and irrigated with regenerated waste water.

Green approach for ultratrace determination of divalent metal ions and arsenic species using total-reflection X-ray fluorescence spectrometry and mercapto-modified graphene oxide nanosheets as a novel adsorbent.

A new method based on dispersive microsolid phase extraction (DMSPE) and total-reflection X-ray fluorescence spectrometry (TXRF) is proposed for multielemental ultratrace determination of heavy metal ions and arsenic species. In the developed methodology, the crucial issue is a novel adsorbent synthesized by grafting 3-mercaptopropyl trimethoxysilane on a graphene oxide (GO) surface. Mercapto-modified graphene oxide (GO-SH) can be applied in quantitative adsorption of cobalt, nickel, copper, cadmium, and lead ions. Moreover, GO-SH demonstrates selectivity toward arsenite in the presence of arsenate. Due to such features of GO-SH nanosheets as wrinkled structure and excellent dispersibility in water, GO-SH seems to be ideal for fast and simple preconcentration and determination of heavy metal ions using methodology based on DMSPE and TXRF measurement. The suspension of GO-SH was injected into an analyzed water sample; after filtration, the GO-SH nanosheets with adsorbed metal ions were redispersed in a small volume of internal standard solution and deposited onto a quartz reflector. The high enrichment factor of 150 allows obtaining detection limits of 0.11, 0.078, 0.079, 0.064, 0.054, and 0.083 ng mL(-1) for Co(II), Ni(II), Cu(II), As(III), Cd(II), and Pb(II), respectively. Such low detection limits can be obtained using a benchtop TXRF system without cooling media and gas consumption. The method is suitable for the analysis of water, including high salinity samples difficult to analyze using other spectroscopy techniques. Moreover, GO-SH can be applied to the arsenic speciation due to its selectivity toward arsenite.

Total reflection X-ray spectrometry (TXRF) for trace elements assessment in edible clams.

The present contribution presents a preliminary investigation of the chemical composition with respect to major, minor, trace, and ultratrace elements in several clam species that are frequently used for human consumption in Portuguese markets and worldwide. In order to use a simple and rapid analytical methodology for clam analysis, energy dispersive X-ray fluorescence (EDXRF) spectrometry and total reflection X-ray fluorescence (TXRF) spectrometry were selected as analytical techniques. The analytical capabilities of TXRF spectrometry were evaluated for the determination of minor and trace elements in commercial edible clams. We compared the direct analysis of powdered suspensions (using different sample amounts and dispersant agents) with the analysis of the digested samples for trace element determination. Inductively coupled plasma mass spectrometry analysis of clam digests was also performed to evaluate the analytical possibilities of TXRF spectrometry for trace and ultratrace analysis.

Liquid phase microextraction strategies combined with total reflection X-ray spectrometry for the determination of low amounts of inorganic antimony species in waters.

In the present study, and taking into account the microanalytical capability of total reflection X-ray spectrometry (TXRF), we explored the possibilities of hollow fibre liquid-phase microextraction (HF-LPME) and dispersive liquid-liquid microextraction (DLLME) combined with TXRF for the determination of low amounts of inorganic Sb species in waters. For each of the LPME configurations aforementioned, experimental parameters affecting Sb extraction but specially the proper sample preparation process (deposition volume on the reflective carrier and drying mode) and measurement conditions for subsequent TXRF analysis have been carefully evaluated. The best analytical strategy for the determination of Sb(III) and Sb(V) in the low µg L(-1) range was found to be the application of the DLLME mode before TXRF analysis. The developed methodology was successfully applied to the determination of inorganic Sb speciation in different types of spiked water samples.