Chemical analysis of argon–oxygen decarburization slags in stainless steelmaking process by X‐ray fluorescence spectrometry

A quantitative analysis method of fluorine in the slags produced in the stainless argon–oxygen decarburization (AOD) process by X‐ray spectrometry was proposed employing direct analysis technique by pressed pellet. This research investigated the separate quantification of calcium fluoride and calcium oxide contained in AOD slags. X‐ray diffraction measurement was performed to identify the stable phase of fluorine compound, which is primarily present in the slags. The synthetic standards prepared in laboratory were used to construct the X‐ray fluorescence (XRF) calibration curves for F, Ca_tO, SiO₂, MgO, Al₂O₃ and Cr₂O₃, considering the matrix effects and line overlap corrections (t: total). The calibration curves were tested by the quantitative analysis of synthetic standards with satisfactory precision and accuracy. The proposed method might be an alternative solution to the problem with the simple and routine chemical analyses of calcium fluoride in AOD slags of stainless steelmaking process by XRF spectrometry. Copyright © 2010 John Wiley & Sons, Ltd.     

A simple calibration procedure of polycapillary based portable micro‐XRF spectrometers for reliable quantitative analysis of cultural heritage materials

Portable micro‐X‐ray fluorescence (micro‐XRF) spectrometers mostly utilize a polycapillary X‐ray lens along the excitation channel to collect, propagate and focus down to few tens of micrometers the X‐ray tube radiation. However, the polycapillary X‐ray lens increases the complexity of the quantification of micro‐XRF data because its transmission efficiency is strongly dependent on the lens specifications and the propagated X‐ray energy. This feature results to a significant and not easily predicted modification of the energy distribution of the primary X‐ray tube spectrum. In the present work, we propose a simple calibration procedure of the X‐ray lens transmission efficiency based on the fundamental parameters approach in XRF analysis. This analytical methodology is best suited for compact commercial and portable micro‐XRF spectrometers. The developed calibration procedure is validated through the quantitative analysis of a broad range of samples with archeological relevance such as glasses, historical copper alloys, silver and gold alloys offering an overall accuracy of less than 10%–15%. Copyright © 2015 John Wiley & Sons, Ltd.     

ED‐XRF set‐up for size‐segregated aerosol samples analysis

The knowledge of size‐segregated elemental concentrations in atmospheric particulate matter (PM) gives a useful contribution to the complete chemical characterisation; this information can be obtained by sampling with multi‐stage cascade impactors. In this work, samples were collected using a low‐pressure 12‐stage Small Deposit Impactor and a 13‐stage rotating Micro Orifice Uniform Deposit Impactor^?. Both impactors collect the aerosol in an inhomogeneous geometry, which needs a special set‐up for X‐ray analysis. This work aims at setting up an energy dispersive X‐ray fluorescence (ED‐XRF) spectrometer to analyse quantitatively size‐segregated samples obtained by these impactors. The analysis of cascade impactor samples by ED‐XRF is not customary; therefore, as additional consistency test some samples were analysed also by particle‐induced X‐ray emission (PIXE), which is more frequently applied to size‐segregated samples characterised by small PM quantities. A very good agreement between ED‐XRF and PIXE results was obtained for all the detected elements in samples collected with both impactors. The good inter‐comparability proves that our methodology is reliable for analysing size‐segregated samples by ED‐XRF technique. The advantage of this approach is that ED‐XRF is cheaper, easier to use, and more widespread than PIXE, thus promoting an intensive use of multi‐stage impactors. Copyright © 2011 John Wiley & Sons, Ltd.     

Transportable EDXRF analysis of environmental water samples using Amberlite IRC748 ion‐exchange preconcentration

Transportable energy‐dispersive X‐ray fluorescence spectrometers allow on‐site assessment of metal‐contaminated soils, sediments and other solids. Multi‐element analysis of liquid samples, such as surface water, groundwater, acid leach and aqueous soil extracts, would enhance on‐site environmental assessments. However, transportable spectrometers typically have detection limits for metals in waters of approximately 1–10 mg l^?1, whereas many toxic elements are regulated at concentrations of 1–100 µg l^?1. If detection limits for this technique can be lowered, then only one analytical tool, a transportable XRF spectrometer, may be sufficient for remote areas, increasing program flexibility and reducing the amount of equipment that needs to be purchased, transported and operated. This research develops an in‐field preconcentration technique using Amberlite IRC748 cation‐exchange resin, followed by XRF analysis of Fe, Ni, Cu, Zn and Pb at µg l^?1 concentrations in aqueous samples. The operational parameters tested to maximise analyte recovery included flow rate, and the mass and chemical form of the resin. The method was tested with extracts from landfill soils and surface waters from a derelict base metal mine. The method recovered Cu, Zn and Pb accurately, and Ni and Fe at concentrations satisfactory for screening purposes. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparison between XRF and EPMA applied to study the ionic exchange in zeolites

Zeolites are crystalline aluminosilicates consisting of SiO₄ and AlO₄ tetrahedral as primary units. One peculiar characteristic of zeolites is the ion exchange capacity defined as the capacity to locate specific cations in the framework of zeolites; it depends on the chemical composition and varies with the structure of the zeolite and with the cation nature. This work studies the exchange of the Na⁺ monovalent cation of 5A and 13X synthetic zeolites by the Ca²⁺ bivalent cation present in a CaCl₂ solution. X‐ray fluorescence (XRF) and electron probe microanalysis (EPMA) techniques were used to determine the cation exchange capacity (CEC). The efficiencies of the two X‐ray detectors were compared and the minimum detection limits of the zeolite elements were calculated. Although both techniques differ in the sample excitation mode, the results obtained were compatible. The results showed that the CEC was higher for the 5A zeolite, in agreement with its lower SiO₂/Al₂O₃ ratio and its greater BET area. It was also found that the amount of Na⁺ ions exchanged by Ca²⁺ ions was in complete agreement with the corresponding molar balance. The determination of the CEC using X‐ray spectroscopy techniques can be considered a novelty as XRF and EPMA techniques permit to analyze the sample directly. Copyright © 2009 John Wiley & Sons, Ltd.     

Methodology for the determination of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF)

This article describes a methodology for the analysis of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF) spectrometry. The methodology was developed in order to have a rapid and reliable control method of these elements, because they determine coke end uses. There are a number of standard methods of chemical analysis by WD‐XRF or inductively coupled plasma atomic emission spectrometry (ICP‐OES) techniques. However, the standards that use WD‐XRF measurement give detection limits (L_D) above 10 mg·kg^?1 and only analyse a few elements of interest, whereas the ICP‐OES method requires extensive sample handling and long sample preparation times, with the ensuing errors. In order to improve the method described in the standard ASTM D6376 and reach the L_D and quantification limits (L_Q) required, the different stages of the process, ranging from sample preparation to measurement conditions: analytical line, detector, crystal, tube power, use of primary beam filters, and measurement time, were optimised. The samples were prepared in the form of pressed pellets, under conditions of high cleanliness of the mills, crushers, presses, and dies, and of the laboratory itself. The following reference materials were used in measurement calibration and validation: SRM 1632c, SRM 2718, SRM 2719, SRM 2685b, AR 2771, AR 2772, SARM 18, SARM 19, and CLB‐1. In addition, a series of materials were analysed by WD‐XRF and ICP‐OES, and the results were compared. The developed methodology, which uses WD‐XRF, is rapid and accurate, and very low L_D and measurement uncertainties were obtained for the following elements: Al, Ba, Ca, Cr, Cu, Fe, Ge, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, and Zn. Copyright © 2010 John Wiley & Sons, Ltd.     

X‐ray fluorescence spectrometry in Dar es Salaam

Energy‐dispersive x‐ray fluorescence (EDXRF) analysis has been established at the University of Dar es Salaam, Faculty of Science, Department of Physics. Calibration was conducted using thin films from Micromatter (USA) for secondary target XRF. We report on the performance of the spectrometer including the detection limits attained, which range from 0.01 to 10 ng cm^?2 using collimators of 6 and 8 mm diameter under excitation conditions of 50 kV, 35 mA. The accuracy of the measurements was checked using IAEA SOIL‐7 and NIST 3087a Certified Reference Materials. The experimental values differed by <5% from the certified values. The total reflection x‐ray fluorescence (TXRF) facility added as a module to the existing XRF system provides detection limits between 0.1 and 100 pg for most of the elements measured. Copyright © 2005 John Wiley & Sons, Ltd.     

Focus on sulfur count rates along marine sediment cores acquired by XRF Core Scanner

The aim of this study is to investigate the information provided by sulfur count rates obtained by X‐ray fluorescence core scanner (XRF‐CS) along sedimentary records. The analysis of two marine sediment cores from the Niger Delta margin shows that XRF‐CS sulfur count rates obtained at the surface of split core sections with XRF‐CS correlate with both direct quantitative pyrite concentrations, as inferred from X‐ray powder diffraction (XRD) and sulfur determination by wavelength dispersive X‐ray fluorescence (WD‐XRF) spectrometry, and total dissolved sulfide (TDS) contents in the sediment pore water. These findings demonstrate the potential of XRF‐CS for providing continuous profiles of pyrite distribution along split sections of sediment cores. The potential of XRF‐CS to detect TDS pore water enrichments in marine sediment records, even a long time after sediment recovery, will be further discussed. Copyright © 2016 The Authors. X‐Ray Spectrometry Published by John Wiley & Sons Ltd.     

X‐ray fluorescence analysis of Cr,As, Se,Cd, Hg,and Pb in soil using pressed powder pellet and loose powder methods

Quantitative analyses of Cr, As, Se, Cd, Hg, and Pb in soil were performed using wavelength dispersive X‐ray fluorescence (WDXRF) spectrometry with pressed powder pellet and loose powder methods. Standard soil samples containing hazardous metals were prepared by adding appropriate amounts of aqueous standards to base soils and then drying and homogenizing them. Base soil powders ground to less than 12.5 µm of modal particle size were Tachikawa loam, brown forest soil, and weathered granite containing 17.9, 9.43, and 3.49 mass% of Fe₂O₃, respectively. Analytical lines were CrKα, AsKα, SeKα, CdKα, HgLα, and PbLβ, with accompanying corrections for overlapping of SeKβ to PbLβ and PbLα to AsKα. Specimens for XRF analysis were prepared using powder pellets pressed to 23 mm internal diameter of an Al ring with 300 kgf cm^?2, and loose powder in a 31 mm internal diameter polyethylene cup covered with 6‐µm thickness of polypropylene film. Calibration curves drawn using the proposed standards showed good linearity under 3000 mg kg^?1 for the five metals, and 300 mg kg^?1 for Hg. Corrections with Compton scattering for AsKα, SeKα, CdKα, HgLα, and PbLβ, and with background scattering for CrKα were effective and produced identical inclinations of calibration curves. CdKα having larger critical depth in the loose powder specimen showed merely smaller inclination of calibration curve than that of the pressed powder specimen because of optical shading. The spike test for five analytes showed good recovery for gravel soil and pumice soil. Copyright © 2009 John Wiley & Sons, Ltd.     

In vivo time‐resolved X‐ray fluorescence mapping measurements of Egeria densa immersed in Cr(VI) aqueous solution

In vivo time‐resolved Cr and Ca X‐ray fluorescence (XRF) mapping measurements were performed in a laboratory over a period of 69 days on a living common aquatic plant Egeria densa that was immersed in 5 mM K₂CrO₄ aqueous solution. The time and spatial resolution for each time‐resolved XRF map were ~1.6 days and 1 × 1 mm², respectively. The obtained XRF maps exhibited characteristic localized Cr and Ca areas where the XRF signals were especially strong (‘hot spots’), and this indicated the necessity of preliminary millimeter‐resolution surveying in XRF microscopy. Ca hot spots were detected prior to Cr(VI) immersion and nearly disappeared after immersion in deionized water for 2 weeks and the Cr(VI) solution for 1 week. After these immersions, a Cr hot spot was formed at approximately the same location of the missing Ca hot spot, which suggests that the original Ca‐accumulated regions were substituted for the isolation of Cr species when they were introduced. The sizes and intensity distributions of the Cr hot spots were sensitive to the Cr(VI) exposure approximately 1 week prior to each XRF measurement. This sensitivity suggests potential applications of E. densa as a Cr(VI) biomonitor in aquatic environments. Copyright © 2014 John Wiley & Sons, Ltd.     

X‐ray‐induced alteration of specimens as crucial obstacle in XRF spectrometry of fluorine in rocks and soils

Occasionally suggested yet rarely performed X‐ray fluorescence (XRF) spectrometry of fluorine seems to fail systematically in yielding reliable quantitative results for rocks and soils. Repeated analyses reveal continuously drifting fluorescence intensities for fluorine, boron and chlorine. Typically, an increase, but in few cases also a decrease, over X‐ray exposure time is observed. For instance, fluorine concentrations in a soil standard appear to increase steadily from below the detection limit in the first run to nearly 850 mg/kg F more than 10 h later in the last. In contrast, cryolite is characterised by drastically decreasing intensities for fluorine. Although fluorescence intensities may be affected by preparation methods, specimen surface conditions and dynamic contamination, it is shown that none of these influencing factors is responsible for the observed trends. In fact, there is evidence that X‐radiation impact mobilises fluorine, boron and chlorine. Diffusion of radiolysis products towards the specimen's surface as well as the kinetics of adsorption and desorption or chemical reactions are believed to control the analyte concentration in the analysed layer decisively. Furthermore, during analysis, the latter is altered by considerable losses of binder or flux – if applicable – thus enhancing XRF intensities of boron and fluorine because of reduced absorption. In any case, signal stability appears to be limited by insufficient sample and specimen stability. It is concluded that for many soil and rock samples, XRF spectrometry is inappropriate to quantify fluorine, although the crucial obstacle is neither the analytical method nor the spectrometer sensu strictu. Copyright © 2012 John Wiley & Sons, Ltd.     

A pigment (CuS) identified by micro‐Raman spectroscopy on a Chinese funerary lacquer ware of West Han Dynasty

A blue pigment was identified by micro‐Raman spectroscopy, X‐ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM)/energy dispersive X‐ray (EDX) and X‐ray diffraction (XRD). The test sample, a funerary lacquer tray, belongs to West Han Dynasty (206 BC–AD 8) of China and was decorated with faint blue patterns. The result from Raman spectroscopy showed that the faint blue is covellite (CuS) due to the presence of a characteristic peak at 474.5 cm⁻¹, which further was confirmed by XRF, SEM–EDX and XRD. This research indicated that CuS had been used as a blue pigment to decorate lacquer wares from the West Han Dynasty in China. Copyright © 2009 John Wiley & Sons, Ltd.     

A sample carrier for measuring discrete powdered samples with an ITRAX XRF core scanner

The elemental composition of discrete powdered sediment samples can be measured by the energy‐dispersive X‐ray fluorescence (XRF) system that is installed in XRF core scanners. Because an appropriate sample carrier for powdered samples is currently not available, for example, for the ITRAX XRF core scanner, such a carrier is presented in this technical note. The designed sample carrier can hold 30 sample cups with a volume of 0.88 cm³ each. A maximum of 5 sample carriers, that is, 150 samples, can be measured in one run. The sample cups and carriers are optimized for a measurement procedure with a step size of 5 mm and variable count times up to 100 s per sample. With this setting, data are collected from an area of 100 mm² in the center of the sample thereby ensuring a good representativeness of the signal because potential sample inhomogeneity is accounted for. Because the described sample carrier system allows rapid element analyses of discrete powdered environmental samples with an XRF core scanner, it may in some cases represent a time‐ and cost‐efficient alternative to conventional XRF analyses.     

X‐ray fluorescence analysis of Co,Ni, Pd,Ag, and Au in the scrapped printed‐circuit‐board ash

A method for the quantitative analysis of Co, Ni, Pd, Ag, and Au in the scrapped printed‐circuit‐board ash by X‐ray fluorescence (XRF) spectrometry using loose powder was developed. The printed‐circuit‐board samples were converted to ash pyrolytically in porcelain crucibles by sequential heating using a gas burner and electric furnace, and then were ground with a ball mill. The calibrating standards were prepared by adding the appropriate amounts of NiO powder and aqueous standard solutions containing Co, Pd, Ag, and Au to the base mixtures of Al₂O₃ (5.0 mass%), SiO₂ (49 mass%), CaCO₃ (11 mass%), Fe₂O₃ (3.3 mass%), and CuO (30 mass%) as a matrix. Then, 10 g of the resulting mixtures were dried and homogenized for 90 min with a V‐type mixing machine. Specimens for XRF analysis were prepared from the so‐called loose‐powder method in which powder samples were compacted into a hole (12.0‐mm diameter and 5.0‐mm height) in an acrylic plate and covered with a 6‐µm thickness of polypropylene film. Matrix effects were corrected using the intensity value of Compton scattering for PdKα, AgKα, and AuLβ₂, and that of background scattering at 35.8° (2θ) for CoKα and NiKα. The detection limits corresponding to three times the standard deviation of the blank intensity were 2.5–45 µg g^?1. The proposed method was validated against the pressed‐powder‐pellet method by comparing the calibration curves. Moreover, the concentrations of Co, Ni, Pd, and Ag determined using the proposed XRF method were approximately the same as those resulting from an atomic‐absorption‐spectrometric analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Analytical Study of Raw Materials of Zinc Oxide Used for Enamels on Industrial Ceramics: Quantitative Analysis of Zinc,Lead, and Sulfur in These Samples by X‐ray Fluorescence and Flame Atomic Absorption Spectrometry

An analytical study is carried out to optimize X‐ray fluorescence (XRF) and flame atomic absorption spectrometry (FAAS) quantitative analysis of Zn, Pb, and S in ZnO samples commonly used to obtain industrial ceramic enamels. Pb and S in the raw materials often contaminate ZnO and are very detrimental in industrial applications. Thus, very accurate analytical determination of these elements in ceramic samples is extremely important. First of all, a mineralogical study by X‐ray diffraction (XRD) on the different components in these raw materials and the materials produced during the firing process is performed in order to establish the mineral forms in a reference sample for analysis by XRF spectrometry. The working conditions are optimized for XRF multielemental analysis, using the sample in the form of pellets, due to high loss on ignition (LOI) values. The preparation of suitable standards and working conditions for FAAS analysis have also been optimized. The content of these elements was determined by FAAS for the reference sample and several samples for industrial use, and the results were compared with those obtained by XRF. Comparison of the results obtained from XRF and FAAS analysis of Pb and Zn show more accurate values for FAAS. For ZnO, an accuracy of 0.11% with ±0.1% precision by FAAS and 0.46% accuracy with ±0.2% precision by XRF are found. For PbO, 1.06% accuracy and ±0.06% precision using FAAS and 5.6% accuracy and ±0.35% precision by XRF were found. For SO₃ determined only by XRF, accuracy was 4.76% with ±0.25% precision. These values are highly satisfactory given that these two elements are only found in small proportions.     

Monte Carlo simulation code for confocal 3D micro‐beam X‐ray fluorescence analysis of stratified materials

Stratified materials are of great importance for many branches of modern industry, e.g. electronics or optics and for biomedical applications. Examination of chemical composition of individual layers and determination of their thickness helps to get information on their properties and function. A confocal 3D micro X‐ray fluorescence (3D µXRF) spectroscopy is an analytical method giving the possibility to investigate 3D distribution of chemical elements in a sample with spatial resolution in the micrometer regime in a non‐destructive way. Thin foils of Ti, Cu and Au, a bulk sample of Cu and a three‐layered sandwich sample, made of two thin Fe/Ni alloy foils, separated by polypropylene, were used as test samples. A Monte Carlo (MC) simulation code for the determination of elemental concentrations and thickness of individual layers in stratified materials with the use of confocal 3D µXRF spectroscopy was developed. The X‐ray intensity profiles versus the depth below surface, obtained from 3D µXRF experiments, MC simulation and an analytical approach were compared. Correlation coefficients between experimental versus simulated, and experimental versus analytical model X‐ray profiles were calculated. The correlation coefficients were comparable for both methods and exceeded 99%. The experimental X‐ray intensity profiles were deconvoluted with iterative MC simulation and by using analytical expression. The MC method produced slightly more accurate elemental concentrations and thickness of successive layers as compared to the results of the analytical approach. This MC code is a robust tool for simulation of scanning confocal 3D µXRF experiments on stratified materials and for quantitative interpretation of experimental results. Copyright © 2011 John Wiley & Sons, Ltd.     

The comparative analytical performance of the Beagle 2 X‐ray Spectrometer for in situ geochemical analysis on Mars

The Beagle 2 X‐ray Spectrometer (B2 XRS) instrument was part of the Beagle 2 Mars lander payload and intended to perform in situ geochemical analyses of geological materials on Mars. The analytical performance of a spare version of the B2 XRS was compared with (1) a portable X‐ray fluorescence (PXRF) spectrometer designed to perform terrestrial fieldwork and (2) a laboratory‐based wavelength‐dispersive (WD‐XRF) system used to produce high quality geochemical data. The criteria used to assess the performance were based on fitting precision, accuracy and detection limit, determined from the analysis of international geochemical reference materials. The fitting precision of the B2 XRS and PXRF was found to be in agreement with the Horwitz function (a benchmark relating the analysed concentration of an analyte to its uncertainty) over 4 orders of magnitude of concentration range from 10^?1 to 10^?5 g/g. The PXRF generally had a better fitting precision than the B2 XRS because of its better resolution. In order of improving accuracy, the spectrometers generally are ranked B2 XRS, PXRF and WD‐XRF for various major and trace elements. A limiting factor in the accuracy of the B2 XRS was the application of the algorithm used for its quantitative analysis. The detection limits for the spectrometers ranked in the same order as the accuracy as a result of improving signal‐to‐noise ratio (SNR) of elemental peaks, which is a direct consequence of improving resolution between these spectrometers. Overall, the B2 XRS was found to have a favourable analytical performance compared to the benchmark spectrometers, despite having met considerable design constraints and qualification tests as a planetary instrument. Copyright © 2009 John Wiley & Sons, Ltd.     

Study of fossil bones by synchrotron radiation micro‐spectroscopic techniques and scanning electron microscopy

Earlymost Villafranchian fossil bones of an artiodactyl and a perissodactyl from the Milia excavation site in Grevena, Greece, were studied in order to evaluate diagenetic effects. Optical microscopy revealed the different bone types (fibro‐lamellar and Haversian, respectively) of the two fragments and their good preservation state. The spatial distribution of bone apatite and soil‐originating elements was studied using micro‐X‐ray fluorescence (µ‐XRF) mapping and scanning electron microscopy. The approximate value of the Ca/P ratio was 2.2, as determined from scanning electron microscopy measurements. Bacterial boring was detected close to the periosteal region and Fe bearing oxides were found to fill bone cavities, e.g. Haversian canals and osteocyte lacunae. In the perissodactyl bone considerable amounts of Mn were detected close to cracks (the Mn/Fe weight ratio takes values up to 3.5). Goethite and pyrite were detected in both samples by means of metallographic microscopy. The local Ca/P ratio determined with µ‐XRF varied significantly in metal‐poor spots indicating spatial inhomogeneities in the ionic substitutions. XRF line scans that span the bone cross sections revealed that Fe and Mn contaminate the bones from both the periosteum and medullar cavity and aggregate around local maxima. The formation of goethite, irrespective of the local Fe concentration, was verified by the Fe K‐edge X‐ray absorption fine structure (XAFS) spectra. Finally, Sr K‐edge extended XAFS (EXAFS) revealed that Sr substitutes for Ca in bone apatite without obvious preference to the Ca₁ or Ca₂ unit‐cell site occupation.     

Chemical speciation via X‐ray emission spectra

Since the early days of X‐ray spectrometry, X‐ray emission and fluorescence spectra have been used to investigate chemical speciation, e.g. the dependence on the formal oxidation state. Laboratory wavelength‐dispersive spectrometers have adequate resolution for these measurements. However, almost all studies have employed empirical methods to interpret the spectra. We aim to place such methods on a quantitative basis by means of efficient ab initio calculations of the X‐ray emission line shapes based on a self‐consistent, real‐space Green's function approach, as implemented in the X‐ray spectroscopy code FEFF8.2. Calculations are presented for the phosphorus K‐M_{2, 3}, and the chromium L‐series emission lines for a selection of simple compounds. These lines exhibit changes depending on the oxidation state and on the neighboring atoms in the compounds that can be observed with instruments available in many XRF laboratories. The calculated spectra, as modified by convolution with a model monochromator response function, are compared with measured spectra. Simulated and measured spectra are found to be in reasonable agreement, and show that the approach has the potential to yield quantitative information about the chemical state. Copyright © 2006 John Wiley & Sons, Ltd.     

Graphene oxide‐based solid phase extraction of vitamin B12 from pharmaceutical formulations and its determination by X‐ray fluorescence

In the present study, a novel quantitative method, namely solid phase extraction, was applied to extract vitamin B₁₂ from pharmaceutical formulations. The technique involves the use of graphene oxide (GO) as an efficient adsorbent for solid‐phase extraction of vitamin B₁₂. Collection of GO from aqueous solution was simply achieved by applying filtration assembly. The extracted analyte was directly analyzed by using X‐ray fluorescence (XRF) spectroscopy. Factors affecting the extraction efficiency were investigated and optimized. Under the optimum conditions, enhancement factor of 46, linear dynamic range of 25–1000 µg l^?1 with correlation of determination (R² = 0.998) and limit of detection of 20 µg l^?1 were obtained for vitamin B₁₂. The percent relative standard deviation based on three‐replicate determination was less than 8.1%. The method was successfully applied for extraction and determination of vitamin B₁₂ in different types of pharmaceutical samples such as multivitamin tablet, effervescent tablet and injection sample. The results showed that the proposed method based on GO was a simple, accurate, and highly efficient approach for analysis of vitamin B₁₂. Copyright © 2014 John Wiley & Sons, Ltd.