Standard X-ray Fluorescence Research Articles

Reference-free x-ray fluorescence analysis with a micrometer-sized incident beam

Spatially resolved x-ray fluorescence (XRF) based analysis employing incident beam sizes in the low micrometer range (μXRF) is widely used to study lateral composition changes of various types of microstructured samples. However, up to now the quantitative analysis of such experimental datasets could only be realized employing adequate calibration or reference specimen. In this work, we extent the applicability of the so-called reference-free XRF approach to enable reference-free μXRF analysis. Here, no calibration specimen are needed in order to derive a quantitative and position sensitive composition of the sample of interest. The necessary instrumental steps to realize reference-free μXRF are explained and a validation of ref.-free μXRF against ref.-free standard XRF is performed employing laterally homogeneous samples. Finally, an application example from semiconductor research is shown, where the lateral sample features require the usage of ref.-free μXRF for quantitative analysis.

Gold nanoparticle detection and quantification in therapeutic MV beams via pair production

Purpose. We propose a new detection method of gold nanoparticles (AuNP) in therapeutic megavoltage (MV) x-ray beams by means of coincidence counting of annihilation photons following pair production in gold. Methods. The proposed MV x-ray induced positron emission (MVIPE) imaging technique is studied by radiation transport computations using MCNP6 (3D) and CEPXS/ONEDANT (1D) codes for two water phantoms: a 35 cm slab and a similarly sized cylinder, both having a 5 cm AuNP filled region in the center. MVIPE is compared to the standard x-ray fluorescence computed tomography (XFCT). MVIPE adopts MV x-ray sources (Co-60, 2 MV, 6 MV, 6 MV with closed MLC and 15 MV) and relies on the detection of 511 keV photon-pairs. XFCT uses kilovoltage sources (100 kVp, 120 kVp and 150 kVp) and imaging is characterized by analysis of k α1,2 Au characteristic lines. Three levels of AuNP concentration were studied: 0.1%, 1% and 10% by weight. Results. Annihilation photons in the MVIPE technique originate both in the AuNP and in water along the x-ray beam path with significantly larger production in the AuNP-loaded region. MVIPE signal from AuNP is linearly increasing with AuNP concentration up to 10%wt, while XFCT signal reaches saturation due to self-absorption within AuNP. The production of annihilation photons is proportional to the MV source energy. MVIPE technique using a 15 MV pencil beam and 10 wt% AuNP detects about 4.5 × 103 511 keV-photons cm−2 at 90° w/r to the incident beam per 109 source photons cm−2; 500 of these come from AuNP. In contrast, the XFCT technique using 150 kVp detects only about 100 k α1-photons cm−2 per 109 source photons cm−2. Conclusions. In MVIPE, the number of annihilation photons produced for different MV-beam energies and AuNP concentrations is significantly greater than the k α1 photons generated in XFCT. Coincidence counting in MVIPE allows to avoid collimation, which is a major limiting factor in XFCT. MVIPE challenges include the filtering of Compton scatter and annihilation photons originating in water.

Mapping of XRF data onto the surface of a tomographically reconstructed historical sculpture

Historical wooden sculptures were usually decorated using so-called polychromy, which consists of decorating in a variety of colors. It is also common that such artifacts have been renovated several times by applying additional layers of material. Currently, restoration approaches tend to return historical artifacts to their original appearance. Therefore, it is highly desirable to investigate the material composition of the existing polychromy. Obviously, information about possible reparations and hidden defects is required as well. It is relatively easy to explore the internal structure of wooden sculptures by utilizing X-ray computed tomography. Standard X-ray fluorescence analysis is typically only performed on several selected spots of the sculpture. On the other hand, X-ray fluorescence imaging can presently characterize the whole artifact surface, although the interconnection between the 2D fluorescence image and the 3D sculpture is not so straightforward in general. It will be shown in this work, that data fusion based on a combination of X-ray fluorescence imaging and computed tomography can provide complex information about the wooden sculpture investigated.

Confocal x‐ray Fluorescence Imaging Facilitates High‐Resolution Elemental Mapping in Fragile Archaeological Bone

Synchrotron‐based standard X‐ray fluorescence imaging can be a sophisticated tool for mapping distributions of trace elements in archaeological bone; however, thin samples are normally required to achieve high‐spatial‐resolution results. Poorly preserved or fragile archaeological samples can be challenging to measure using this standard technique, since the production of a sufficiently thin section may be difficult. We discuss the implementation of confocal X‐ray fluorescence imaging as a successful strategy for high‐resolution elemental mapping in poorly preserved archaeological bone. The implementation of the confocal method additionally can facilitate localized quantification and speciation of elements, which are also discussed.

In situ investigation of the surface silvering of late Roman coins by combined use of high energy broad-beam and low energy micro-beam X-ray fluorescence techniques

The compositional analysis of archeological metals performed with the X-ray Fluorescence technique (XRF) provides information on the ancient technology. One of the most interesting case-study concerns the techniques used by Romans for silvering the surface of coins. Different metallurgical processes have been suggested in previous studies. Recently the investigation has been addressed to the mercury-silvering and to its possible use in the mass-production of coins minted during the late period (after 294AD).In the present paper the non-destructive investigation of the silvering process used for manufacturing the Roman nummi – the important typology of coin introduced by Diocletian in his monetary reform – is approached by the combined use of the standard X-Ray Fluorescence (XRF) and the low energy micro-X-Ray Fluorescence (LE-μXRF) portable methods. The research was focused on the systematic determination of the mercury presence in a large number of samples and on its correlation with silver in the surface of the coins.1041 Roman nummi belonging to the Misurata Treasure were analyzed in situ, at the Leptis Magna Museum (Al Khums, Libya). The treasure, composed of about 108 thousand silvered coins, gives the unique opportunity to study the Roman coinage in a wide interval of time (about 40years in the period 294–333AD) and in almost all the imperial mints operating in the Roman world.

Analysis of Beverages for Hg, As, Pb, and Cd with a Field Portable X-Ray Fluorescence Analyzer

Analytical capabilities of a handheld X-ray tube analyzer for analysis of beverages were evaluated. Sets of standard solutions for the elements Hg, As, Pb, and Cd were prepared with mass fractions up to 5000 mg/kg. A thirst quencher beverage was spiked with these elements up to mass fractions of 2500 mg/kg. Portions of these solutions were placed in standard X-ray fluorescence (XRF) cells, as well as the original container, and analyzed by using a field portable Innov-X alpha-6000s XRF tube-type analyzer. Uncorrected analyzer output usually yielded qualitative or semiquantitative results for the spiked beverages in X-ray cells. Average correction factors applied to analyzer output yielded accurate (in terms of z-scores) quantitative results for As above 20 mg/kg and qualitative or semiquantitative results for the other elements. Weighted quadratic fit calibrations provided accurate quantitative or semiquantitative results for all elements at levels above 20 mg/kg. The instrument's preset X-ray overlap correction algorithm worked well for the beverage spiked with all four elements. Spiked beverages analyzed through the wall of the original polyethylene terephthalate container produced accurate results within measurement uncertainties after application of "container wall" correction factors.

Interaction of nickel and manganese in accumulation and localization in leaves of the Ni hyperaccumulators Alyssum murale and Alyssum corsicum

The genus Alyssum contains >50 Ni hyperaccumulator species; many can achieve >2.5% Ni in dry leaf. In soils with normal Mn levels, Alyssum trichome bases were previously observed to accumulate Ni and Mn to high levels. Here we report concentration and localization patterns in A. murale and A. corsicum grown in soils with nonphytotoxic factorial additions of Ni and Mn salts. Four leaf type subsets based on size and age accumulated Ni and Mn similarly. The greatest Mn accumulation (10 times control) was observed in A. corsicum with 40 mmol Mn kg−1 and 40 mmol Ni kg−1 added to potting soil. Whole leaf Ni concentrations decreased as Mn increased. Synchrotron X-ray fluorescence mapping of whole fresh leaves showed localized in distinct high-concentration Mn spots associated with trichomes, Ni and Mn distributions were strongly spatially correlated. Standard X-ray fluorescence point analysis/mapping of cryofractured and freeze-dried samples found that Ni and Mn were co-located and strongly concentrated only in trichome bases and in cells adjacent to trichomes. Nickel concentration was also strongly spatially correlated with sulfur. Results indicate that maximum Ni phytoextraction by Alyssum may be reduced in soils with higher phytoavailable Mn, and suggest that Ni hyperaccumulation in Alyssum species may have developed from a Mn handling system.

Slag analysis with laser-induced breakdown spectrometry.

Laser-induced breakdown spectrometry (LIBS) has been applied for multi-elemental analysis of slag samples from a steel plant. In order to avoid the time-consuming step of sample preparation, the liquid slag material can be filled in special probes. After cooling of the liquid slag and solidification, the samples can be analyzed with LIBS. Chemical analysis of slag is an essential input parameter used for numerical simulations to control liquid steel processing. The relative variation range of element concentrations in slag samples from steel production can amount to up to 30%. A multivariate calibration model is used to take into account matrix effects caused by these varying concentrations. By optimizing the measuring parameters as well as the calibration models, an agreement between the standard X-ray fluorescence (XRF) analysis and LIBS analysis in terms of the coefficient of determination r2 of 0.99 for the main analytes CaO, SiO2, and Fetot of converter slag samples was achieved. The average repeatability of the LIBS measurement for these elements in terms of the relative standard deviation of the determined concentration is improved to less than 1.0%. With these results, the basis is established for future on-line applications of LIBS in the steel-making industry for slag analysis.

Trends, applications and results in X-ray fluorescence analysis

X-ray fluorescence (XRF) has reached a mature state and represents a powerful analytical tool for the qualitative and quantitative determination of almost all the chemical elements in a sample. Standard XRF methods as well as special techniques to improve the detection limits will be presented, emphasizing the versatility of the method. With modern instrumentation the detectable number of elements ranges from Be to U. The minimum detectable quantities under optimizied excitation and detection conditions for medium Z elements are a few hundred femtograms. Other features like rapid analysis because of the multielement capability and in some cases the nondestruction of the sample are advantageous for a wide field of applications.

Quantitative major- and trace-element whole-rock analyses by secondary-ion mass spectrometry using the specimen isolation technique

Rapid accurate quantitative major- and trace-element bulk-chemical analyses of whole rocks are made using secondary-ion mass spectrometry (SIMS). An extreme form of energy filtering (specimen isolation technique) removes virtually all molecular species from the spectrum, as demonstrated by the lack of molecular ions and isotope ratio studies. Rock samples are fused in Pb 2SiO 4 to yield a glass pellet of “constant composition” which circumvents matrix problems and yields workable and reproducible calibration curves for analyses of unknown samples. Up to 48 of the 54 elements quoted for the international standards can be readily analyzed. Twenty elements at the major, minor and trace levels have been analyzed, both in international standards and in unknown samples, using the technique. Analyses generally are accurate to within 5% of quoted values for the major elements and to within 10% for the trace elements. Use of other standards may yield still more accurate results. The limits of detection compare favourably with standard X-ray fluorescence (XRF) methods for many of the heavier elements and are much better for most of the light elements, particularly Li, B, Na, Mg and P, some third-series transition elements and the lanthanides. The SIMS method is an excellent companion to the standard XRF techniques. The procedures are simple and very rapid with 20–25 elements analyzed accurately and routinely per hour; hence eight samples can be analyzed per day for 20–25 elements. The method yields results at the weight percent and ppm levels with equal ease and rapidity.

The geochemistry of the Turriff metavolcanics, Grenville Province, southeastern Ontario

Fifty-seven samples of the Turriff metavolcanic sequence from the Hastings region of the Grenville Province have been chemically analyzed. Ten major-element oxides and ten trace-element values for each sample were determined by standard X-ray fluorescence techniques. The sampled sections consist predominantly of mafic flows, subordinate intermediate flows, and minor felsic flows and pyroclastics. The sequence has been regionally metamorphosed to lower amphibolite facies. The geochemical data indicate that the metavolcanics represent a tholeiitic mafic–silicic bimodal sequence. Immobile-element discriminant diagrams indicate that the Turriff metabasalts are most similar to recent oceanic ridge basalts, whereas the metabasalts from other published studies of Grenville metavolcanics have an island-arc tholeiite affinity. However, because of the many chemical similarities between continental and oceanic ridge tholeiites, the bimodal nature of the sequence, and the field relationships, it is most likely that the eruption of the Turriff metavolcanics was associated with the rifting of continental crust, perhaps leading to the development of a marginal sea.

Proterozoic mafic syenites from Baker Lake, N.W.T., Canada

The petrography and major-element chemistry of the Martell Syenite, a Paleohelikian sub-volcanic intrusion, and of some flows of the Christopher Island Formation of the Dubawnt Group, south of Baker Lake, are described. The chemical analyses were carried out using standard X-ray fluorescence techniques. The major-element chemistry of these rocks shows them to be only mildly alkalic. Elemental ratios K 2O/Na 2O, K/Rb, Rb/Ba, and elemental contents of CaO, Rb, Ba, Sr, Zr, U and Th suggest that the syenite has shoshonitic affinities. This is supported by the stratigraphic and structural relationships of the syenite with a volcanic sequence containing mafic trachyte and latite flows. It is concluded that the Martell Syenite is part of a shoshonitic association of volcanic rocks which erupted during the late stages of the Hudsonian Orogeny as the crust thickened and became stable. The chemical characteristics of these rocks suggest that they have been derived by partial melting of an ultramafic source material at mantle pressures. The rising magma may have become enriched in incompatible elements by the process of zone refining. It is suggested that the field relationships and composition of this rock suite indicate that processes similar in kind, but different in degree, to modern plate-tectonic processes were operational from the early Proterozoic.

Machine for silvering looking glasses

The compositional analysis of archeological metals performed with the X-ray Fluorescence technique (XRF) provides information on the ancient technology. One of the most interesting case-study concerns the techniques used by Romans for silvering the surface of coins. Different metallurgical processes have been suggested in previous studies. Recently the investigation has been addressed to the mercury-silvering and to its possible use in the mass-production of coins minted during the late period (after 294 AD).In the present paper the non-destructive investigation of the silvering process used for manufacturing the Roman nummi – the important typology of coin introduced by Diocletian in his monetary reform – is approached by the combined use of the standard X-Ray Fluorescence (XRF) and the low energy micro-X-Ray Fluorescence (LE-μXRF) portable methods. The research was focused on the systematic determination of the mercury presence in a large number of samples and on its correlation with silver in the surface of the coins.1041 Roman nummi belonging to the Misurata Treasure were analyzed in situ, at the Leptis Magna Museum (Al Khums, Libya). The treasure, composed of about 108 thousand silvered coins, gives the unique opportunity to study the Roman coinage in a wide interval of time (about 40 years in the period 294–333 AD) and in almost all the imperial mints operating in the Roman world.