Atomic spectrometry update. X-ray fluorescence spectrometry

This annual review of X-ray fluorescence covers developments over the period 2006–2007 in instrumentation and detectors, matrix correction and spectrum analysis procedures, X-ray optics and micro-fluorescence, synchrotron XRF, TXRF, portable XRF and on-line applications as assessed from the published literature. The review also covers a survey of applications, including sample preparation, geological, environmental, archaeological, forensic, biological, clinical, thin films, chemical state and speciation studies. Interest continues in micro-analytical instrumentation with synchrotron-based systems benefiting from the availability of more intense beams and efficient focusing optics. Many authors have strengthened the influence of their work with data presented as elemental maps and, where appropriate, factor analysis continues to feature. In common with other analytical techniques, this review demonstrates the emerging field of metallomics to assist in the understanding of how metals and metalloids interact within cells and tissues. Progress continues to support legislation with further analytical methods and reference materials available for environmental and industrial applications. Improvements in detector resolution and excitation optics have helped to strengthen interest in EDXRF systems to meet the demands from society for a reduction in pollutants in ambient air. The writing team would welcome feedback from readers of this review and invite you to complete the Atomic Spectroscopy Updates questionnaire on www.asureviews.org

Aerosol particle chemical characteristics measured from aircraft in the lower troposphere during ACE-2

Tellus (ACE-2 Special Issue), 52B, 185-200.During the Aerosol Characterization Experiment (ACE-2), filter samples were collected aboard the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Pelican aircraft near Tenerife in June and July of 1997. The flights included constant altitude measurements in the boundary layer as well as profiles up to 3800 m providing detailed chemical information about the composition of the aerosol distribution in the lower troposphere. Three cases with different air mass origins — clean marine air, anthropogenically-influenced air from the European continent, and dust-laden air from the Sahara — were identified. The samples were analyzed by ion chromatography (IC) for ionic species, by combined thermal and optical analysis (TOA) for organic carbon, and by total reflection X-ray fluorescence (TXRF) for elemental composition. Particle composition and size distributions for the range of air masses encountered illustrate links in the chemical and microphysical characteristics of aerosol from different sources. Clean marine air masses were characterized by low particle number and mass concentrations with no detectable metals, while anthropogenically-influenced and dust-laden air had high number, mass, and trace metal concentrations. Anthropogenic sources were characterized by high concentrations of submicron particles and some Fe and Cu, whereas dust particle loadings included a significant mass of micron-sized particles and significant loadings of Fe, in addition to small amounts of Mn, Cu, and Ni. These results showed similar tracers for air mass origin as those found in other measurements of oceanic and continental air masses. Aerosol optical properties were estimated with a simplified model of the aerosol based on the measured compositions. The real and imaginary refractive indices and single scattering albedos differed significantly among the three types of aerosol measured, with clean marine aerosol properties showing the least absorption and dust-containing aerosols showing the most. There were only small differences in optical properties for the two different cases of clean marine aerosol, but some significant differences between the two dust cases. Since measurement uncertainties affect these calculations, we studied the type of mixing and the fraction of absorbing species and found the calculation was sensitive to these variations only for the dust-containing aerosol case, probably due to the small amount of water present. While the optical properties varied little with composition for clean marine and anthropogenically-influenced cases, they showed a strong dependence on variations in particle composition and mixing state for the dust-containing cases

Study of selenium sorption processes in volcanic ash using Total Reflection X-ray Fluorescence (TXRF)

International audienceSelenium (Se) cycling around volcanoes has implications for human health given the high population density close to volcanoes and the narrow range between essential and toxic Se intake. To study the Se mobility during interaction between volcanic derived acid rain and volcanic ash, new analytical approaches are required. This paper explores the Total Reflection X-Ray Fluorescence (TXRF) for Se determination using sorption processes on volcanic ash as a geochemical application. Our experiments reveal the importance of the anion content of the rainwater for Se mobility in volcanic ash samples. Desorption studies of a weathered volcanic soil using the application of a dispersive liquid-liquid microextraction procedure (DLLME) to isolate Se prior to TXRF analysis (LOD 0.7 mu g/L) revealed much higher level of released Se in sulfuric acid rain compared to hydrochloric acid rain. Additionally, the dominance of selenate in the leaching solution suggests adsorption competition with sulfate as a Se release mechanism. Kinetic adsorption experiments using direct TXRF with as little as 10 mu L. solution (LOD 0.4-8 mu g/L depending on the sample characteristics) showed that the anions present play a key role in the selenite adsorption on volcanic ash by competitive behavior and/or changes in the pH conditions promoted by glass dissolution processes. Our experiments show the high potential of TXRF in such applications. Similarly, TXRF can be used as an analytical tool to study the mobility of trace elements in other geochemical studies

Study of selenium sorption processes in volcanic ash using Total Reflection X-ray Fluorescence (TXRF)

Selenium (Se) cycling around volcanoes has implications for human health given the high population density close to volcanoes and the narrow range between essential and toxic Se intake. To study the Se mobility dur- ing interaction between volcanic derived acid rain and volcanic ash, new analytical approaches are required. This paper explores the Total Reflection X-Ray Fluorescence (TXRF) for Se determination using sorption pro- cesses on volcanic ash as a geochemical application. Our experiments reveal the importance of the anion con- tent of the rainwater for Se mobility in volcanic ash samples. Desorption studies of a weathered volcanic soil using the application of a dispersive liquid-liquid microextraction procedure (DLLME) to isolate Se prior to TXRF analysis (LOD 0.7μg/L) revealed much higher level of released Se in sulfuric acid rain compared to hydrochloric acid rain. Additionally, the dominance of selenate in the leaching solution suggests adsorption competition with sulfate as a Se release mechanism. Kinetic adsorption experiments using direct TXRF with as little as 10μL solution (LOD 0.4–8μg/L depending on the sample characteristics) showed that the an- ions present play a key role in the selenite adsorption on volcanic ash by competitive behavior and/or changes in the pH conditions promoted by glass dissolution processes. Our experiments show the high po- tential of TXRF in such applications. Similarly, TXRF can be used as an analytical tool to study the mobility of trace elements in other geochemical studiesThisworkwassupportedbytheEuropeanCommissionSixthFrame-work Programme (2002–2006) Research Training Network AquaTRAIN(ContractNo.MRTN-CT-2006-035420),theSpanish“Consolider Ingenio2010”Program (Project ref. SD2006-00044), the Spanish National Research Program (Project ref. CGL2007-66861-C4) and the proposer Integrated Activity of Excellence and Networking for Nano and Micro-Electronics Analysis (Project ref. ANNA_TA_UC7_RP003)Peer Reviewe

Atomic layer deposition to prevent metal transfer from implants: An X-ray fluorescence study

We show that Atomic Layer Deposition is a suitable coating technique to prevent metal diffusion from medical implants. The metal distribution in animal bone tissue with inserted bare and coated Co–Cr alloys was evaluated by means of micro X-ray fluorescence mapping. In the uncoated implant, the migration of Co and Cr particles from the bare alloy in the biological tissues is observed just after one month and the number of particles significantly increases after two months. In contrast, no metal diffusion was detected in the implant coated with TiO2. Instead, a gradient distribution of the metals was found, from the alloy surface going into the tissue. No significant change was detected after two months of aging. As expected, the thicker is the TiO2 layer, the lower is the metal migration