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Detection of lead in bone phantoms and arsenic in soft tissue phantoms using synchrotron radiation and a portable x-ray fluorescence system
Get PDFThe differences and commonalities between x-ray fluorescence results obtained using synchrotron radiation and a portable x-ray fluorescence device were examined using arsenic in soft tissue phantoms and lead in bone phantoms. A monochromatic beam energy of 15.8 keV was used with the synchrotron, while the portable device employed a rhodium anode x-ray tube operated at 40 kV. Bone phantoms, dosed with varying quantities of lead, were made of Plaster of Paris and placed underneath skin phantoms of either 3.1 mm or 3.9 mm thickness. These skin phantoms were constructed from polyester resin, and dosed with varying amounts of arsenic. Using an irradiation time of 120 seconds, arsenic Kα and Kβ, and lead Lα and Lβ characteristic x-ray peaks were analysed. This information was used to calculate calibration line slopes and minimum detection limits for each data set. As expected, minimum detection limits were much lower at the synchrotron for detecting arsenic and lead. Both approaches produced lower detection limits for arsenic in soft tissue than for lead in bone when simultaneous detection was attempted. Although arsenic Kα and lead Lα emissions share similar energies, it was possible to detect both elements in isolation by using the arsenic Kβ and lead Lβ characteristic x-rays. Greater thickness of soft tissue phantom reduced the ability to detect the underlying lead. Experiments with synchrotron radiation could help guide future efforts toward optimizing a portable x-ray fluorescence in vivo measurement device.This is the Accepted Manuscript version of an article accepted for publication in Physiological Measurement. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6579/aa513
Optimization of L-shell X-ray fluorescence detection of lead in bone phantoms using synchrotron radiation
No full textClosely-related toxicity and retention mechanisms of lead (Pb) in the human body involve the bone tissues where Pb can accumulate and reside on a time scale ranging from years to tens of years. In vivo measurements of bone Pb can, therefore, play an important role in a comprehensive health risk assessment of Pb exposure. In vivo L-shell X-ray fluorescence (LXRF) measurement of bone Pb was first demonstrated over four decades ago. Implementation of the method, however, encountered challenges associated with low sensitivity and calibration procedure. In this study the LXRF measurement was optimized by varying the incident photon energy and the excitation-detection geometry. The Canadian Light Source synchrotron radiation was used to compare two different excitation detection geometries of 90° and 135° using three different X-ray photon energies: 15.8, 16.6, and 17.5 keV. These energies optimized excitation of the L3 subshell of Pb and simulated the most intense K-shell emissions of zirconium, niobium, and molybdenum, respectively. Five rectangular plaster-of-Paris bone phantoms with Pb concentrations of 0, 7, 17, 26, and 34 μg⁄g and one rectangular 3.1 mm-thick resin phantom mimicked the X-ray attenuation properties of human bone and soft tissue, respectively. Optimal LXRF detection was obtained by the 15.8 keV energy and the 90° and 135° geometries for the bare bone and the bone and soft tissue phantoms, respectively.D. F. would like to acknowledge the financial support of the Natural Sciences and Engineering Research Council (NSERC) of Canada Discovery Grant 261523.This is the peer reviewed version of the following article: Gherase, M. R., Feng, R., & Fleming, D. E. B. (2017). Optimization of L-shell X-ray fluorescence detection of lead in bone phantoms using synchrotron radiation. X-Ray Spectrometry, 46(6), 537–547. https://doi.org/10.1002/xrs.2792 which has been published in final form at https://doi.org/10.1002/xrs.2792
This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited
Portable x-ray fluorescence for the analysis of chromium in nail and nail clippings
Get PDFAssessment of chromium content in human nail or nail clippings could serve as an effective biomarker of chromium status. The feasibility of a new portable x-ray fluorescence (XRF) approach to chromium measurement was investigated through analysis of nail and nail clipping phantoms. Five measurements of 180s (real time) duration were first performed on six whole nail phantoms having chromium concentrations of 0, 2, 5, 10, 15, and 20µg/g. Using nail clippers, these phantoms were then converted to nail clippings, and assembled into different mass groups of 20, 40, 60, 80, and 100mg for additional measurements. The amplitude of the chromium Kα characteristic x-ray energy peak was examined as a function of phantom concentration for all measurement conditions to create a series of calibration lines. The minimum detection limit (MDL) for chromium was also calculated for each case. The chromium MDL determined from the whole nail intact phantoms was 0.88±0.03µg/g. For the clipping phantoms, the MDL ranged from 1.2 to 3.3µg/g, depending on the mass group analyzed. For the 40mg clipping group, the MDL was 1.2±0.1µg/g, and higher mass collections did not improve upon this result. This MDL is comparable to chromium concentration levels seen in various studies involving human nail clippings. Further improvements to the portable XRF technique would be required to detect chromium levels expected from the lower end of a typical population.This work was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada. Equipment was partially funded through the New Brunswick Health Research Foundation.This is an accepted manuscript made available under a CC BY-NC-ND license. The published journal article is available at https://doi.org/10.1016/j.apradiso.2016.12.02
Diboron(4) compounds: From structural curiosity to synthetic workhorse
Get PDFAlthough known for over 90 years, only in the past two decades has the chemistry of diboron(4) compounds been extensively explored. Many interesting structural features and reaction patterns have emerged, and more importantly, these compounds now feature prominently in both metal-catalyzed and metal-free methodologies for the formation of B-C bonds and other processes.This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes
Assessing arsenic and selenium in a single nail clipping using portable X-ray fluorescence
Get PDFThe feasibility of measuring arsenic and selenium contents in a single nail clipping was investigated using a small-focus portable X-ray fluorescence (XRF) instrument with monochromatic excitation beams. Nail clipping phantoms supplemented with arsenic and selenium to produce materials with 0, 5, 10, 15, and 20 μg/g were used for calibration purposes. In total, 10 different clippings were analyzed at two different measurement positions. Energy spectra were fit with detection peaks for arsenic Kα, selenium Kα, arsenic Kβ, selenium Kβ, and bromine Kα characteristic X-rays. Data analysis was performed under two distinct conditions of fitting constraint. Calibration lines were established from the amplitude of each of the arsenic and selenium peaks as a function of the elemental contents in the clippings. The slopes of the four calibration lines were consistent between the two conditions of analysis. The calculated minimum detection limit (MDL) of the method, when considering the Kα peak only, ranged from 0.210 ± 0.002 μg/g selenium under one condition of analysis to 0.777 ± 0.009 μg/g selenium under another. Compared with previous portable XRF nail clipping studies, MDLs were substantially improved for both arsenic and selenium. The new measurement technique had the additional benefits of being short in duration (~3 minutes) and requiring only a single nail clipping. The mass of the individual clipping used did not appear to play a major role in signal strength, but positioning of the clipping is important.This work was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada.This is an accepted manuscript made available under CC BY-NC-ND. The published journal article is available at https://doi.org/10.1016/j.apradiso.2016.11.01
Short-term response of a downstream marine system to opening a tidal-river causeway
Get PDFThe spill gates of the causeway on the Petitcodiac River in New Brunswick, Canada, were permanently opened in April 2010. We examined the short-term effect this had on downstream intertidal mudflats of the upper Bay of Fundy. Specifically, a before-after-control-impact design was used to determine if the causeway opening affected the invertebrate community (crustaceans, polychaetes, and molluscs), abiotic sediment conditions (sediment water content, mean particle size, penetrability, and aRPD depth), or resource availability (sediment chlorophyll a concentration, and organic matter content) of 5 intertidal mudflats (2 impacted sites, 3 reference sites) up to 5 months post-opening. We detected no biologically or statistically meaningful differences between impacted and reference sites for any of the measured variables. This suggests that opening the causeway did not have an impact on these intertidal mudflats, at least within half a year of the opening. We speculate that this is likely a result of the macrotidal nature of the Bay of Fundy, that overwhelmed any changes to hydrodynamics and sedimentation which occurred after the opening of the causeway.This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s12237-016-0173-
Diet reconstruction using next-generation sequencing increases the known ecosystem usage by a shorebird
Get PDFMolecular scatology and next-generation sequencing identified previously unknown linkages among ecosystems in the diet of Semipalmated Sandpipers (Calidris pusilla) in the Bay of Fundy, Canada. During their annual migratory stopover, sandpipers consumed a wider range of prey items than previously thought, suggesting that they are not selecting for the amphipod Corophium volutator, and are acting as generalist foragers. Our analysis identified several novel prey items – arachnids, crabs, bivalves, several terrestrial and freshwater insect species, ctenophores, cnidarians, and fish (likely eggs or juveniles) – indicating that sandpipers consume prey from marine, freshwater, and terrestrial ecosystems. Connections between sandpipers and freshwater as well as terrestrial ecosystems were previously unknown in the Bay of Fundy. Current conservation efforts directed towards sandpipers focus on beach and intertidal habitats; however, we may also need to consider the surrounding freshwater and terrestrial habitat.This is a pre-copyedited, author-produced version of an article accepted for publication in The Auk following peer review. The version of record is available online at: https://academic.oup.com/auk/article/133/2/168/514915
Comparing different types of phytoplankton community measurements to develop an optimal harmful algae monitoring strategy
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