Photon Induced X-ray Fluorescence Research Articles

미국 서부 해안 IMPROVE 측정소에 대한 대기 중 PM2.5의 오염원 기여도 추정

In this study, the chemical compositions of samples collected at the Redwood National Park IMPROVE site in California from March 1988 to May 2004 were analyzed to provide source identification and apportionment. A total of 1,640 samples were collected and 33 chemical species were analyzed by particle induced X-ray emission, proton elastic scattering analysis, photon induced X-ray fluorescence, ion chromatography, and thermal optical reflectance methods. Positive matrix factorization (PMF) was used to develop source profiles and to estimate their mass contributions. The PMF modeling identified five sources and the average mass was apportioned to motor vehicle (35.8%, ), aged sea salt (23.2%, ), fresh sea salt (21.4%, ), wood/field burning (16.1%, ), and airborne soil (3.5%, ), respectively. To analyze local source impacts from various wind directions, the CPF and NPR analyses were performed using source contribution results with the wind direction values measured at the site. These results suggested that sources of are also sources of visibility degradation and then source apportionment studies derived for are also used for understanding visibility problem.

Estimation of source apportionment and potential source locations of PM 2.5 at a west coastal IMPROVE site

Particle composition data for PM 2.5 samples collected at Kalmiopsis Interagency Monitoring of Protected Visual Environments (IMPROVE) site in southwestern Oregon from March 2000 to May 2004 were analyzed to provide source identification and apportionment. A total of 493 samples were collected and 32 species were analyzed by particle induced X-ray emission, proton elastic scattering analysis, photon-induced X-ray fluorescence, ion chromatography, and thermal optical reflectance methods. Positive matrix factorization (PMF) was used to estimate the source profiles and their mass contributions. The PMF modeling identified nine sources. In the Kalmiopsis site, the average mass was apportioned to wood/field burning (38.4%), secondary sulfate (26.9%), airborne soil including Asian dust (8.6 %), secondary nitrate (7.6%), fresh sea salt (5.8%), OP-rich sulfate (4.9%), aged sea salt (4.5 %), gasoline vehicle (1.9%), and diesel emission (1.4%). The potential source contribution function (PSCF) was then used to help identify likely locations of the regional sources of pollution. The PSCF map for wood/field burning indicates there is a major potential source area in the Siskiyou County and eastern Oregon. The potential source locations for secondary sulfate are found in western Washington, northwestern Oregon, and the near shore Pacific Ocean where there are extensive shipping lanes. It was not possible to extract a profile directly attributable to ship emissions, but indications of their influence are seen in the secondary sulfate and aged sea salt compositions.

Biomedical applications of photon-induced X-ray fluorescence

An X-ray fluorescence method for in vitro analysis of trace elements is presented. The method is characterized by the use of an X-ray tube with secondary targets as a quasimonoenergetic radiation source, and by "infinitely thin" specimens.Different aspects have been examined in order to optimize the sensitivity of the method. It is extremely important to use secondary targets as pure as possible and collimators internally covered by the same element as the secondary target. It is also important to reduce the contribution at the XRF spectrum of photons scattered by the sample, by the sample support, and by the air.Preconcentration techniques can conveniently also be used to this purpose. In this work, biological samples are preconcentrated by reducing them to ash.Typical sensitivities obtained are in the order of 1-5 ng/cm(2) in a counting time of 10(3) s for elements with atomic number ranging from 24 (chromium) to 40 (zirconium).

Analysis of Urinary Calculi Using Photon Induced X‐ray Fluorescence (XRF)

Photon induced X-ray fluorescence has been employed to determine trace elements in urinary calculi. Twenty-one urinary stones, classified in four groups, have been analysed. Besides Ca, elements Fe, Zn and Pb were detected, and Cr and Mn were also detected in some cases. No clear differences were found between the four groups.

Contribution to the radionuclide X-ray fluorescence analysis of human blood and plasma

A photon-induced X-ray fluorescence method, which allows the simultaneous determination of iron, copper, zinc, bromine and rubidium in human blood and blood plasma samples is described. The method is reliable and has a good sensitivity for a wide range of elements.

Measurements of elemental composition in background aerosol on the west coast of Sweden

Concentrations of 14 elements in long distance transported aerosol have been measured in a rural site on the W coast of Sweden. The measurements were made during one winter and two summer periods, 1981–1984. Sampling was made with a dichotomous virtual impactor. Element analysis was made by photon induced X-ray fluorescence. The element concentrations were related to air mass trajectories. A strong dependence of the concentration variations with air mass history is found for most elements, in particular Pb, S, V, Zn and Cl. Median concentrations for the 14 elements in the two size fractions are reported and compared with previous measurements in central Sweden at the same latitude. Significant deviations are found for S and V. Concentrations of particulate S have proven to be very insensitive to locally produced SO 2 emissions. This makes measurements of fine particulate S on the Swedish W coast an excellent tool for checking the S transport from other countries to Sweden. The ratios Br Pb in fine particles and the coarse/fine ratios for particulate lead have, together with air mass trajectories, been used to suggest source areas for automotive lead. The soil derived elements, Fe, Ca, Ti and Mn, also demonstrate variations with air mass trajectories. Enrichment factors for coarse particles of Ca, Mn and Ti with iron as a reference show variations that we believe are typical for the soil of the source area.

Analytical application of total reflection and polarized X-rays

Detection limits in photon induced X-ray fluorescence analysis (XRF) using energy dispersive spectrometer systems (ED) can be improved by the application of special excitation conditions. 1. Total reflection of the primary beam of the plane and smooth surface of a reflector reduces the radiation induced background. In total reflection geometry the beam scarcely penetrates into the medium. Taking the reflector as the substrate, only an extremely thin layer of the reflector (20–70 nm) acts as scatterer of the primary photons. The geometry allows efficient excitation of the sample and optimal detection of the fluorescent signal as the detector can be mounted close to the sample. Thin film samples are placed on the reflector-substrate. The sample volume needs only to be a few microliter. Concentrations in the ppb level or absolute amounts of pg can be detected in special cases. Total reflection XRF will be a method of choice if low concentrations in small volumina have to be detected. 2. Linear polarized X-rays are used in an orthogonal beam geometry (x-y-z) to reduce the background from scattered radiation from sample and substrate. Several possibilities to produce polarized X-rays are discussed and proposals made to increase the intensity of the polarized beam after a 90° Bragg reflection from a single crystal. Samples can be of any kind and shape. Detection limits are at present under good excitation conditions at the sub ppm level or in the range of about 100 pg absolute. The application of XRF in the pg range may therefore be extended to practically all kinds of samples if only special care in the sample preparation technique is taken.

The analysis of ruthenium catalysts by photon-induced X-ray fluorescence using a microcomputer for data acquisition and analysis

An improved method for the determination of ruthenium in catalytic materials based on a relative fluorescence ratio factor is presented. This method employs a thin-film technique and an internal standard technique to minimize absorption and enchancement effects. The samples and standards were fluorescent with a109Cd (7 mCi) annular source for 200 seconds and the data were collected and analyzed with an Apple II+ micro computer. Precision (total variation) for typical ruthenium catalysts in the range of 1–5% ruthenium was about 2%. Finally, the concentration of ruthenium in six commercial catalysts was determined for both alumina and carbon supports.

The design of an X-ray microprobe at the SRS Daresbury (UK)

Synchrotron radiation proves to be an excellent source for photon induced X-ray fluorescence (XRF). The radiation is white over a broad wavelength range, highly linearly polarized, confined into a small solid angle and has a high intensity. The polarization facilitates a strong reduction of the background in XRF element analysis. The high intensity and large cross section yield a good applicability for trace element analysis. A doubly bent Si(111) crystal combined with a diaphragm as a design for a photon microprobe was numerically examined to focus synchrotron radiation. Beam size, flux and spectral distribution at the focus have been calculated. The study revealed a beamsize of 50 × 50 μm 2 containing enough flux to obtain a detection limit of 10 −7 weight fraction g g in a measuring time of about 5 s per pixel. In a first try out with a focusing crystal with radius of R = 600 mm a beam intensity of 10 11 photons in a spot of about 300 μm has been achieved.

Elemental Analysis of Canadian, European and American Wines by Photon Induced X-Ray Fluorescence

The photon induced X-ray fluorescence technique was used to determine the distribution of P, S, Cl, K and Ca contents in 231 Canadian, American and European wines. On the average, red wines contained more P, S and K and less Ca than white wines. In red wines, the P content was lowest in Portuguese wines, while high in Spanish and French wines. American red wines were richest in S, while Canadian and French wines contained the most Cl and K. White wines from the United States contained the highest amounts of Ca and relatively high amounts of P, S, Cl, and K; Spanish wines contained lowest P and K contents while French wines had lowest S and Cl contents, and Portuguese wines were lowest in Ca. Elemental variations may be attributed to the provenance and variety of grapes, as well as the fermentation process in each country.

The determination of strontium and yttrium in Venezuelan laterites from Cerro Impacto by both energy- and wavelength-dispersive X-ray fluorescence

A rapid and simple analytical method for the simultaneous determinations of strontium and yttrium in lateritic material from Cerro Impacto, Estado Bolívar, Venezuela, is presented. This method employs an internal-standard-thin-film procedure employing a PDP®-11/05 processor-based photon-induced X-ray fluorescence system. The values determined for strontium and yttrium by this method are compared with conventional wavelength-dispersive X-ray fluorescence, using a chromium X-ray tube for excitation. The concentration varied from values below the detection limit to ∼ 1000 ppm for both, strontium and yttrium in these laterites.

Trace element analysis of filter and impactor samples of atmospheric aerosols by photon induced X-ray fluorescence

Energy dispersive photon induced X-ray fluorescence analysis is applied to atmospheric aerosols. The aerosol samples are taken with a three step air dust impactor and a filter sampler. The impactor and the filter sampler are first compared with each other with regards to their efficiencies to collect airborne trace elements. Under the chosen experimental conditions, the filter sampler collects three to five times more iron and zinc than the impactor. The distribution of heavy metals in the different particle sizes of air dust at the chosen sampling place is then investigated on aerosol samples from the three step cascade impactor. Most of the iron and zinc is located in the particle size range below 3.5 μm. The distribution of both elements in particles of different size ranges remains relatively constant over the observation time. Zinc containing dust appears to be finer than iron containing dust.

The Simultaneous Determination of Thorium, Niobium, Lead, and Zinc by Photon-Induced X-ray Fluorescence of Lateritic Material

A rapid method is presented for the simultaneous determinations of thorium, niobium, lead, and zinc in lateritic material from Cerro Impacto, Estado Bolívar, Venezuela. This technique uses a PDP—11/05 processor—based photon induced x-ray fluorescence system. The total variations of approximately 5% for concentrations of approximately 1 and 10% for concentrations of approximately 0.1% were obtained with only 500 s of fluorescent time. The values obtained by this method were in agreement with values measured by conventional flame atomic absorption spectroscopy for lead and zinc. The values for thorium measured were in agreement with the reported values for the reference materials supplied by NBL.

Comparison of analytical methods for the determination of trace amounts of strontium and yttrium by photon induced X-ray fluorescence techniques in lateritic materials

Three different analytical methods for the determination of strontium and yttrium in Venezuelan latterites by radioisotope induced X-ray fluorescence are compared, also with results from conventional wavelength dispersive X-ray fluorescence. The samples analyzed were from Cerro Impacto, Venezuela. The photon-induced energy dispersive X-ray fluorescence system consisted of a109Cd (7 mCi) source for excitation of the characteristic K X-rays for strontium and yttrium. The detection system employed a high resolution Si(Li) detector and was completely controlled by a PDP-11/05 processor. Of the three analytical methods described, the internal standard-thin film technique was shown to be slightly superior to the conventional standard calibration curve method and the standard additon/dilution procedure. This can be explained by considering the effectiveness of the compensation of the sources of errors by these methods. It should also be noted that in the case of wavelength dispersive X-ray fluorescence, an about 5–10 times greater sample is needed, which is a limitation compared to energy dispersive X-ray fluorescence in some cases. Finally, typical relative standard deviations of the energy dispersive X-ray fluorescence methods were about 10–15% for the range of about 100–100 ppm of strontium and yttrium; these values are acceptable considering the large degree of heterogeneity in this type of geological material.

X-ray fluorescence analysis in the nanogram region with a total reflected and a Bragg polarized primary beam

Improvements of the detection limit in photon induced X-ray fluorescence analysis are obtained by the reduction of the radiation background at constant excitation conditions. Two methods are presented: 1) Bragg-reflection at 2 ν=90° results in a beam linearly polarized and monchromatic. Positioning the detector at an angle 90° to the direction of the polarized beam suppresses the production of scattered photons from sample and sample carrier into the detector. The use of single crystals instead of amorphous scattering materials increases the intensity of the polarized beam, in some cases up to a factor 104. Detection limits and actually used crystal materials and lattice planes for Braggreflection are given in tables. Samples may be of either form, liquid or solid, no special sample preparation is required. 2) The application of X-ray total reflection on the polished and plane surface of a reflector which serves as the sample carrier reduces the radiation background. In the case of X-ray total reflection there is scarcely a penetration of the X-rays into the reflector material. The penetration depth of some 100 A in the reflector-substrate can be compared to an extreme thin foil of same thickness. Therefore the reflector-substrate combines its mechanical strenght, its compact and constant geometric form, its chemical resistance and the possibility of easy handling-with the low background properties of ultra-thin foils. Samples should be liquids where the liquid part of the matrix is evaporated and the remaining trace elements are investigated. Both method are capable of detecting elements in the nanogram region.

The simultaneous determinations of cobalt, nickel and molybdenum in hydrodesulfurization catalysts by photon induced X-ray fluorescence

A rapid radioisotope induced energy-dispersive X-ray fluorescence procedure for the simultaneous determinations of Cobalt, Nickel and Molybdenum in hydrodesulfurization catalysts is presented. A109Cd (7 mCi) source is used as the excitation system coupled to a high resolution Si(Li) detector. A PDP-11/05 processor is employed as a multichannel analyzer and also to automatically control the complete system by means of a prewritten computer program. The relative standard deviations for the three determinations (CoO, NiO and MoO3) are less than 5% for 300 seconds of fluorescent time for a typical sample. Finally a comparison of results by different methods is given to check the accuracy since no standard reference materials are available for catalytic material.

X-ray fluorescence analysis of airborn particulates in an industrial Greek city

Photon induced X-ray fluorescence is used at a medium sized Greek industrial city, to detect trace elements with 20≤Z≤40 in airborn particulates collected on filter papers.

Determination of trace elements in whole blood by photon-induced X-ray fluorescence.

Photon-induced X-ray fluorescence is used to determine elements in human whole blood samples. The method is reliable and has a good sensitivity for a wide range of elements. The simplicity of the technique and the associated instruments makes the method suitable for use in hospitals.

Search for superheavy elements in monazite from beach sands of South India

Monazite minerals obtained from beach sands of South India were examined for the presence of superheavy elements with photon-induced x-ray fluorescence method. The accumulated data of a number of runs each of several days duration do not show any convincing peaks above the background at the expected locations for superheavy elements which are above the present sensitivity of detection of about 10 ppm by weight for element 126. However, some intriguing features pertaining to structures in the x-ray spectra around 27 keV were observed, which are of interest for further investigations.

Thin target thickness measurement by photon induced x-ray fluorescence

The method of photon induced X-ray fluorescence is applied to determine thickness of targets deposited on any backing and intended for use in nuclear physics experiments.