Rh X-ray Tube Research Articles

Foliar analysis via portable X-ray fluorescence spectrometry: Experimental considerations

Portable X-ray fluorescence spectrometry (pXRF) is a well-known and accepted method for earth-materials analysis. It is also promising for analysis of plant tissues. However, some factors must be assessed in order to obtain a protocol for plants mainly for in-field measurements of intact and fresh leaves. This work defines an experimental approach for two distinct plant leaves (Spinach and Post Oak) considering water content (94% and 52% w/w, respectively) and anatomy. Using a commercial pXRF system equipped with a Rh X-ray tube, some conditions for in-situ and ex-situ analysis were assessed to obtain the concentrations of macro (P, K, Ca, Mg, and S) and micronutrients (Fe, Zn, Cu, and Mn). For in-situ applications, the penetration of X-rays through Pinus wood was evaluated. In this case, the goal was to propose a simple way to scan fresh and intact plant leaves in the field, using the wood as a background stage. Thus, the minimum wood thickness to avoid any influence of soil surface was investigated. Afterward, the following factors were assessed: i) the effect of water content; ii) the number of overlapped and pressed leaves on pXRF results; iii) the effect of adaxial or abaxial leaf surface. For ex-situ applications, the thickness of oven-dried and ground (< 0.6 mm) plant material packed into pXRF sample cup was tested. After pXRF analysis, the sum of all elements in the wood corresponded to only 0.91% having no significant influence on elemental composition of the leaves. In a qualitative manner, intact and fresh leaves can be placed on a 1-cm thick Pinus wood stage for analysis. Comparing fresh and dry leaves, water did have an effect on reported elemental concentrations, mainly for spinach leaves. For Post Oak leaves there was also an effect caused by water content but less than spinach, suggesting that for leaves with low water content (e.g., <50%) the effect of water content may be small. For both studied plant leaves there was no effect of adaxial or abaxial surface. For ex-situ analysis of oven-dried and ground plant material, the thickness in the sample cup must be strongly considered. This work suggests at least 1 cm thickness is required for accurate readings; thickness >1 cm is desirable. pXRF analysis of fresh and intact plant leaves in the field is possible in a qualitative manner.

FLUKA Simulations of Kβ/Kα Intensity Ratios of Copper in Ag-Cu Alloys.

The numerical simulations of Cu and Cu fluorescence lines induced by Rh X-ray tube and by monoenergetic radiation have been presented. The copper intensity ratios for pure elements as well as for Ag–Cu alloys have been modeled. The results obtained by use of the FLUKA code, based on the Monte-Carlo approach, have been compared to available experimental and theoretical values. A visible relationship was found between the simulated intensity ratios and the copper content of the Ag–Cu alloy: As the Cu content increases, the coefficient decreases. The results can play role in elemental material analysis, especially in archaeometry.

X-Ray fluorescence analysis of Mexican varieties of dried chili peppers

X-ray Fluorescence (XRF) was used to perform elemental analyses of samples of Mexican varieties of dried chili peppers. Specimens of nine varieties of Capsicum annuum L. (ancho, morita, chilpotle, guajillo, pasilla, mulato, piquín, puya, and árbol) were analyzed to determine the contents of 12 elements (P, S, Cl, K, Ca, Mn, Fe, Cu, Zn, Br, Rb, and Sr). There are mainly two types of samples: one bought as packaged chilies in markets and the second one as unpackaged products in street markets. The aim of this work to establish differences in the elemental concentrations of each category and compare with home-grown samples previously analyzed (varieties of Capsicum annuum L., Capsicum chinense, and Capsicum pubescens). The samples were freeze dried and deposited in plastic vials. XRF analyses were performed with a Rh X-ray tube spectrometer and a Si-PIN detector. The system detection calibration was achieved using NIST standard reference materials 1547 (peach leaves), 1574 (tomato leaves), and 1570A (spinach leaves), while analytical accuracy was verified with the standard reference material 1571 (orchard leaves). Measured elemental concentrations for each variety are presented and extract dissimilarities with Cluster Analysis plus Principal Component Analysis. The results showed mainly five groups, each one characterized by different elements.

Determination of the Kβ/Kα intensity ratios of silver in Ag-Cu alloys

The Ag-Kα and Ag-Kβ fluorescence lines induced by Rh X-ray tube have been observed. The Ag Kβ/Kα intensity ratios for pure Ag and for Ag-Cu alloys have been obtained. The results have been compared with multi-configuration Dirac-Hartree-Fock predictions and available experimental values. Strong dependence between measured Kβ1,3/Kα1,2 and Kβ1,2,3/Kα1,2 ratios and the composition of Ag-Cu alloy has been found out. For both ratios the same tendency is visible: decrease of the Kβ/Kα intensity ratios with increasing of Ag content.

Space-resolved determination of the mineral nutrient content in tree-rings by X-ray fluorescence

X-ray fluorescence spectroscopy (XRF) offers rapid, multi-elemental, low cost and non-destructive elemental analysis. Different studies have used this technique to investigate distribution and concentration of essential and deleterious elements in vegetation. Special emphasis has been recently placed on the key aspects concerning sampling processes, laboratory protocols and calibration methods for quantitative analysis. The aim of the present study was to develop a quantitative methodology to determine the nutrient content in Pinus taeda tree-rings by XRF. Using a 1 mm X-ray excitation beam from a Rh X-ray tube at 30 kV and 600 μA, and dwell time of 20 s, we present calibration curves for P, S, K, Ca, Mn and Fe based on multi-elemental standard addition using wood matrix of 17-year-old Pinus taeda trees. Satisfactory recoveries of our XRF approach for Ca, P, Mn, S and K (<115%), and tolerable for Fe (123%) were obtained compared to inductively coupled plasma optical emission spectrometry results. The non-destructive and quantitative XRF method allows assessing annual element concentrations of P. taeda trees, in order to provide tools for monitoring the nutrient dynamic in an experimental plantation. Furthermore, a method for elemental quantification based on multi-elemental standard addition using wood matrix is described as a useful procedure for future applications.

Simplifying Sample Preparation for Soil Fertility Analysis by X-ray Fluorescence Spectrometry.

Portable X-ray fluorescence (pXRF) sensors allow one to collect digital data in a practical and environmentally friendly way, as a complementary method to traditional laboratory analyses. This work aimed to assess the performance of a pXRF sensor to predict exchangeable nutrients in soil samples by using two contrasting strategies of sample preparation: pressed pellets and loose powder (<2 mm). Pellets were prepared using soil and a cellulose binder at 10% w w−1 followed by grinding for 20 min. Sample homogeneity was probed by X-ray fluorescence microanalysis. Exchangeable nutrients were assessed by pXRF furnished with a Rh X-ray tube and silicon drift detector. The calibration models were obtained using 58 soil samples and leave-one-out cross-validation. The predictive capabilities of the models were appropriate for both exchangeable K (ex-K) and Ca (ex-Ca) determinations with R2 ≥ 0.76 and RPIQ > 2.5. Although XRF analysis of pressed pellets allowed a slight gain in performance over loose powder samples for the prediction of ex-K and ex-Ca, satisfactory performances were also obtained with loose powders, which require minimal sample preparation. The prediction models with local samples showed promising results and encourage more detailed investigations for the application of pXRF in tropical soils.

Dual energy-band excitation from a low power Rh anode X-ray tube for the simultaneous determination of low Z and high Z elements (Na-U) using total-reflection X-ray fluorescence analysis (TXRF).

This article presents results from an experimental setup for a dual energy-band vacuum spectrometer for total-reflection X-ray fluorescence analysis allowing simultaneous efficient excitation of low, medium, and high Z elements. The spectrometer is equipped with an air-cooled 35 W low power Rh X-ray tube and a 17 mm2 silicon drift detector with a thin 8 µm beryllium window. A Pd/B4C multilayer monochromator is used at the same time as a Bragg reflector for Rh-Kα radiation and as a high-energy cut-off reflector above 5 keV, where the characteristic Rh-L radiation is totally reflected and present in the spectrum of the exciting radiation. This leaves one broad low energy band below 5 keV and one high energy band around the energy of Rh-Kα. As Rh-L radiation would be absorbed on its path through air, a new beam entrance system was designed in order to guide the Rh-L photons into the vacuum chamber for efficient excitation of low Z elements. With this setup, elements down to sodium (Z = 11, E = 1.04 keV) could be detected. First results are presented, and spectra obtained in air as well as in vacuum are compared and discussed. Detection limits in the range of 1000 µg/kg for Na and around 140 µg/kg for Mg were achieved using the NIST SRM 1640 (trace elements in water).

PIXE and XRF elemental analysis of breakfast cereals consumed in Mexico

Elemental concentrations in breakfast cereals consumed in Mexico were measured using Particle induced X-ray emission with 1.7 MeV protons and X-ray fluorescence with a Rh X-ray tube operating at 35 kV. The specimens, obtained from packages purchased in markets, were freeze dried, ground and pelletized. Standardization was done with tomato, spinach, peach, and orchid leaves NIST standard reference materials, and analytical accuracy verified with NIST 3233 standard reference material (fortified cereal). The concentrations of nine elements did not agree with values quoted in the packages. Therefore, there may be inaccurate official estimations of Mexican population nutrient intakes.

X-Ray Fluorescence Analysis of Ground Coffee.

Coffee is becoming one of the most popular beverages in Mexico. In the present work, X-ray Fluorescence (XRF) was used to determine the contents of several elements (with atomic numbers between 11 and 38) in 11 samples of commercial ground coffee, comparing with another one of soluble coffee and two of used ground coffee. Samples were dried at room temperature and pelletized. XRF analyses were carried out using a spectrometer based on an Rh X-ray tube, registering the characteristic x-rays with a Silicon Drift Detector. The system detection calibration and accuracy check was performed through the analysis of NIST certified reference materials 1547 (peach leaves), 1570a (spinach leaves), 1573a (tomato leaves), and 1571 (orchid leaves). As a general rule, the elemental concentrations measured are similar in all samples of coffee, in values not exceeding toxic levels. However, the differences among the elemental concentrations are shown.

X-Ray Fluorescence Analysis of Fine Atmospheric Aerosols from a Site in Mexico City

A study was performed in the Winter of the year 2015 in a Southwestern site in the MAMC (Ciudad Universitaria), collecting PM2.5 samples with a Mini Vol. As a part of wider study focused to fully characterize aerosols at this site, an X-ray Fluorescence (XRF) spectrometer (based on an Rh X-ray tube) built to analyze environmental samples, was used to characterize the sample set. A total of 16 elements (Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb) were detected in most samples and mean concentrations were calculated. Cluster analysis was also applied to the elemental concentrations to find possible correlations among the elements.

Analysis of a Roman Centaurus from Canas de Senhorim (Portugal)-Comparative study using EDXRF and SXRF

A decoration figure of a ritual bronze vase from Canas de Senhorim (Portugal) was analysed by Energy Dispersive X-Ray Fluorescence (EDXRF) spectromttly and Synchrotron Inducted X-Ray Fluorescence (SXRF) microprobe spectrometry. This artefact, a CenSuas constitutesthe first evidencefor a possible Roman occupation of this region of central Portugal and it is also one of the very few artefacts of this type ever found. The determination of the Centaurus alloy composition will be important in the flurthercomprehension of the metallurgical technologies used by the Romans in this region. EDXRF analysis of the corroded surface were made using the monochromatic radiation emitted by Ag and Gd secondary targets excited by a Rh X-ray tube at 35kV and 57 kV, respectively. SXRF experiments were carried out both on the corroded surface and on a small clean area of the artefact, using both monochromatic and polychromaticexcitations with 32 key and 12 keV radiations. EDXRF results allowed the determination of the alloy bulk composition. The SXRF comparative analysis between the clean and corroded are evidences the surface enrichment in Sn and establishes the composition of the original alloy. The Cenlaurus alloy is a bronze with rather high Pb content, which is characteristic of the Roman decorative artefacts.

X-Ray Fluorescence Cross-Section Measurements in the Energy Range 4-18 keV

K, L and M shell x-ray fluorescence cross sections have been measured for elements 11 ≤, Z ≤, 92 at excitation energies corresponding to weighted average energies of K-lines of Ti-K (4.558 keV), Fe-K (6,480 keV), Ge-K (10.024 keV), Se-K (11.391 keV) and Mo-K (17.805 keV) . The measurements were performed with an energy-dispersive x-ray spectrometer in a vacuum chamber using thin ultra-pure targets. Rh x-ray tube and secondary targets were used for excitation of x-ray radiation. The measured x-ray fluorescence cross-sections have been compared to previously published experimental and theoretical results. Presented data can be used for determination of physical parameters such as photoionization cross-sections, fluorescence yields, x-ray emission rates, Coster-Kronig transition probabilities and jump ratios.

X-ray irradiation effects on ErBa2Cu3O7− x superconducting thin films

ErBa 2Cu 3O 7− x superconducting thin films prepared on MgO single-crystal substrates by RF magnetron sputtering were irradiated with X-rays emitted from an Rh X-ray tube for 100 h. The superconducting properties were damaged to disappear the zero-resistance state and then were recovered by oxygen annealing at 450°C. No change in the crystallinity causing the radiation damage was observed in the X-ray diffraction patterns. The X-ray photoemission spectra showed that the mean Cu valence was close to +1 after the irradiation and was increased to about +2 by the annealing. The X-ray irradiation must induce oxygen vacancies, which can be filled by the oxygen annealing.