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

Estudi del comportament de les nanopartícules de plata en sòls agrícoles

En aquest treball, s’han dut a terme estudis d’adsorció en discontinu i tests de lixiviació per a entendre els processos d’adsorció/desorció de les nanopartícules de plata (AgNP) en els sòls. S’ha observat que les AgNP presenten una retenció ràpida i una mobilitat baixa en els sòls i tenen un paper important la capacitat d’intercanvi catiònic i la conductivitat elèctrica del sòl, així com la càrrega superficial i la mida de les AgNP. Tres setmanes després d’estar en contacte amb el sòl, la majoria de les AgNP mantenen la seva nanoforma. L’aplicació de l’extracció en punt de núvol (cloud-point extraction) permet caracteritzar acuradament les AgNP en mostres que contenen plata iònica

Evaluation of different analytical approaches using total reflection X-ray fluorescence systems for multielemental analysis of human tissues with different adipose content

Publisher Copyright: © 2022 The AuthorsElemental content plays an important role in biological processes, and so, the multielemental analysis of human tissue samples is required in biomedical research. Still, the small amount of available biological samples and the adipose content of the samples can be major setbacks for the accurate determination of elemental content. In this study, we explored the potential of several analytical approaches combined with total reflection X-ray fluorescence spectrometry (TXRF) for multielemental analysis of human tissues with different adipose content (colon, heart, liver, lung, muscle, intestine, skin, stomach, uterus, bladder and aorta). The capabilities and limitations of different sample treatment procedures (suspension and acidic digestion) and two TXRF systems with different anode configurations (Mo and W X-ray tubes) have been evaluated for such purpose. Results showed that for tissues with a higher fat content (e.g., skin, and intestine) the best strategy was the acidic digestion of the sample before TXRF analysis. However, for other tissues, acceptable results were obtained by suspending 20 mg of powdered material in 1 mL of 2 M nitric acid. A further enhancement of the limits of detection and accuracy of the results was achieved if using Mo-TXRF systems, especially for the determination of low Z elements (e.g., K, and Ca) and of elements present at low concentrations (e.g., Cu) in the human tissues. Finally, results by TXRF analysis were compared with those obtained with μ-EDXRF and ICP-OES, and a good agreement was obtained.publishersversionpublishe

Estudi del comportament de les nanopartícules de plata en sòls agrícoles

En aquest treball, s'han dut a terme estudis d'adsorció en discontinu i tests de lixiviació per a entendre els processos d'adsorció/desorció de les nanopartícules de plata (AgNP) en els sòls. S'ha observat que les AgNP presenten una retenció ràpida i una mobilitat baixa en els sòls i tenen un paper important la capacitat d'intercanvi catiònic i la conductivitat elèctrica del sòl, així com la càrrega superficial i la mida de les AgNP. Tres setmanes després d'estar en contacte amb el sòl, la majoria de les AgNP mantenen la seva nanoforma. L'aplicació de l'extracció en punt de núvol (cloud-point extraction) permet caracteritzar acuradament les AgNP en mostres que contenen plata iònica.In this paper, batch adsorption studies and leaching tests have been performed to understand silver nanoparticle (AgNP) adsorption/desorption processes in soils. AgNPs show fast retention and low mobility in soils, with an important role being played by the cation exchange capacity and electrical conductivity of soils as well as by the surface charge and size of AgNPs. After three weeks of contact with soils, most AgNPs retain their nanoform. The application of cloud-point extraction allows an accurate AgNP characterization in samples containing ionic silver

Analytical methodologies based on X-Ray Fluorescence Spectrometry (XRF) and Inductively Couple Plasma Spectroscopy (ICP) for the assessment of metal dispersal around mining environments

La investigació que es presenta en aquesta tesi es centra en l'aplicació i millora de metodologies analítiques existents i el desenvolupament de nous procediments que poden ser utilitzats per a l'estudi dels efectes ambientals de la dispersió dels metalls entorn a les zones mineres abandonades.En primer lloc, es van aplicar diferents procediments d'extracció simple i seqüencial per a estudiar la mobilitat, perillositat i bio-disponibilitat dels metalls continguts en residus miners de característiques diferents. Per altra banda, per a estudiar les fonts potencials de Pb en la vegetació de les zones mineres d'estudi, una metodologia basada en la utilització de les relacions isotòpiques de Pb determinades mitjançant ICP-MS va ser avaluada. Finalment, tenint en compte l'elevat nombre de mostres analitzades per a avaluar l'impacte de les activitats mineres, es va considerar apropiat el desenvolupament de mètodes analítics d'elevada productivitat. En aquest sentit la implementació d'estratègies quantitatives així com l'aplicació de les millores instrumentals en els equips de XRF han estat avaluades per a aconseguir resultats analítics fiables en l'anàlisi de plantes. A més, alguns paràmetres de qualitat com la precisió, l'exactitud i els límits de detecció han estat curosament determinats en les diverses configuracions de espectròmetres de XRF utilitzats en el decurs d'aquest treball (EDXRF, WDXRF i EDPXRF) per a establir la capacitat de la tècnica de XRF com a tècnica alternativa a les clàssiques comunament aplicades en la determinació d'elements en mostres vegetals.The research presented in this thesis is based on the application and improvement of analytical existing methodologies and the development of novel procedures that can be used to assess the environmental effects on metal dispersal around abandoned mining activities. On the one hand, single and sequential extraction procedures were properly applied in order to study the potential mobility, risk and bioavailability of the metals contained in several mining wastes of different features. On the other hand, in an attempt to study the potential sources of the anomalous lead content in vegetation specimens growing on the waste and soils of abandoned mining areas, a methodology based on the use of stable lead isotope ratios using ICP-MS instrumentation was evaluated.Finally, in view of the considerable number of vegetation specimen analysis necessary to assess the impact of mining activities, the study of high productivity analytical methods for metal determination in this kind of matrices was considered appropriate. In this sense, the implementation of suitable quantitative strategies and the recent improvements in the XRF instrumentation have been evaluated to achieve reliable analytical results for plant analysis. Besides, analytical figures of merit such as precision, accuracy and limits of detection have been carefully determined in the diverse configurations of XRF spectrometers employed in the course of this work (EDXRF, WDXRF, EDPXRF) using different excitation sources in order to assess the capability of XRF as an alternative analytical tool to classical destructive methodologies, commonly applied for the determination of elements in vegetation matrices

Determination of cadmium at ultratrace levels in environmental water samples by means of total reflection X-ray spectrometry after dispersive liquid-liquid microextraction

Until now, the determination of Cd at trace levels in aqueous samples by TXRF has been restricted. When Mo-target X-ray tubes are used, low sensitivity and interferences with Cd L-lines used for quantification prevent trace analysis. Alternatively, when W-target X-ray tubes are used Cd excitation is limited. For this reason, a sample pretreatment is usually necessary to extract, isolate and concentrate Cd prior to TXRF analysis. In the present contribution, the feasibility of a dispersive liquid-liquid microextraction approach (DLLME) combined with TXRF for ultratrace Cd determination in different types of environmental waters is shown. Parameters affecting the extraction procedure and TXRF measurement conditions have been carefully evaluated to ensure the highest sensitivity for Cd determination. Using the best analytical conditions, it was found that the minimum cadmium content that could be detected in an aqueous solution was 0.04 μg L-1. This value is more than two orders of magnitude lower compared with the direct TXRF analysis of Cd in aqueous samples. The precision of the methodology was evaluated in terms of relative standard deviation (RSD) of six replicate analyses of a standard solution containing 3 μg L-1. The precision of the method was determined to be approximately 5% RSD. In order to test the suitability of the method when dealing with complex matrices as well as the influence of interfering ions, the determination of Cd in spiked water samples (sea water, estuarine water and river water) at the levels of 1 μg L-1 and 5 μg L-1 was undertaken and Cd added to the samples was quantitatively determined. Our results give insight into the possibilities of the combination of DLLME and TXRF for ultratrace Cd determination in different types of environmental waters. © 2013 The Royal Society of Chemistry.This work was supported by the Spanish National Research Progam (Project ref. CGL2010-22168-C03-01)Peer Reviewe

X-ray fluorescence for multi-elemental analysis of vegetation samples

Presently, the development of analytical methods to determine elemental composition of vegetation samples is of significance in many different fields. This chapter discusses the details and potentials of different X-ray fluorescence (XRF) configurations in the field of multi-elemental analysis of vegetation samples. Most commonly used sample treatment procedures are also described. The chapter includes some of the many interesting applications of XRF in environmental and agronomic studies dealing with the analysis of vegetation samples. Some of the main advantages of XRF in the field of vegetation sample analysis over other atomic spectroscopic techniques include the simplicity of sample preparation and the possibility to determine elements such as P, S, Cl, and Br which can be of significance in biological processes.Peer reviewe

Dispersive micro solid-phase extraction using multiwalled carbon nanotubes for simultaneous determination of trace metal ions by energy-dispersive x-ray fluorescence spectrometry

A methodology based on dispersive micro solid-phase extraction (DMSPE) using multiwalled carbon nanotubes (MWCNTs) as solid sorbent prior to measurement with energy-dispersive X-ray fluorescence (EDXRF) spectrometry is proposed. The procedure consists of chelating of nickel, cobalt, copper, and lead ions with ammonium pyrrolidinedi-thiocarbamate (APDC) and posterior adsorption of metal chelates on MWCNTs (1 mg) dispersed in the aqueous samples (100 mL). DMSPE promotes immediate interaction between the metal chelates and MWCNTs and shortens time of sample preparation in comparison with classical solid-phase extraction. After microextraction process, MWCNTs are collected onto filter and directly measured by EDXRF. With this technique, the direct quantification of metal species held in solid materials is possible and, therefore, the elution step can be avoided. The effects of various experimental parameters such as pH of the solution, amounts of MWCNTs and APDC, sample volume, and time of stirring were investigated. With the best analytical conditions (1 mg of MWCNTs, 2 mg of APDC, 100 mL sample volume, pH = 7, and 5 min time of stirring), Co(II), Ni(II), Cu(II), and Pb(II) can be simultaneously determined with very good recoveries (101%, 98%, 96%, 99%, respectively) and detection limits (0.43, 0.11, 0.46, 0.15 ng mL>1, respectively). The method was applied in determination of trace metal ions in tap water and wastewater samples. © 2013 Society for Applied Spectroscopy.This work was supported by the Spanish National Research Program (Project ref. CGL2010-22168-C03-01).Peer Reviewe

Application of X-ray fluorescence spectrometry to determination and quantitation of metals in vegetal material

Determination of the chemical composition of vegetal matrices in the environmental and industrial fields has been increasing in the past few years. For analysis of vegetal specimens, X-ray fluorescence (XRF) spectrometry provides the desired features, including multi-element capability, simple sample preparation, wide dynamic range, high throughput and low cost per determination. This article gives an overview of the state of the art of XRF spectrometry for elemental determination and quantitation in vegetal samples. We give a brief description of sample-preparation procedures and then discuss physical and chemical effects of matrices involved when dealing with vegetal materials. We give special attention to current instrumentation, and we highlight advantages and limitations of each configuration. We comment on trends and the future outlook for XRF spectrometry in this application.This work was supported by the Spanish National Research Program (Project CGL2007-66861-C4). E. Marguí gratefully acknowledges the research contract from the Spanish Council for Scientific research (CSIC, JAE-Doc Program).Peer reviewe