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“Computer simulation of an analytical direct current glow discharge in argon: influence of the cell dimensions on the plasma quantities”. Bogaerts A, Gijbels R, Journal of analytical atomic spectrometry 12, 751 (1997)
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.379
Times cited: 21
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“Analysis of platinum powder by glow discharge mass spectrometry”. van Straaten M, Swenters K, Gijbels R, Verlinden J, Adriaenssens E, Journal of analytical atomic spectrometry 9, 1389 (1994). http://doi.org/10.1039/ja9940901389
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.466
Times cited: 17
DOI: 10.1039/ja9940901389
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“Characteristics of atomic absorption calibration curves with the transversely heated graphite furnace”. Bencs L, Szakács O, Szoboszlai N, Ajtony Z, Bozsai G, Journal of analytical atomic spectrometry 18, 105 (2003). http://doi.org/10.1039/B208198A
Abstract: Calibration curves with two quasi-linear sections ("double sloping'') were observed for the medium volatile elements, Cr and Cu, with the use of a SIMAA 6000 graphite furnace atomic absorption spectrometer under interrupted internal gas flow conditions. If a standard transversally heated graphite atomizer (THGA) tube was shortened by 0.5 mm at both of its ends, (i.e. the gaps were enlarged between graphite furnace housing and tube ends), a stronger declination of the calibration curves resulted. Elements with fairly high diffusion coefficients (>5.8 cm(2) s(-1)) and with short appearance time of their transients (<0.6 s), such as Cr and Cu, have shown the most characteristic sensitivity drop towards higher concentrations. This anomalous feature could be eliminated in three different ways; (1) by applying end-capped THGA tubes, (2) using mini-flow (50 cm(3) min(-1)) conditions during the atomization stage, and (3) by adding Pd-Mg chemical modifier. For the low volatile Mo and V, the calibration curves had no irregular shape. For Ag, Co, Cr, Cu, Mn and Ni, the mini-flow settings improved the linearity of the calibration curves and extended the upper limit of the linear calibration range by a factor of 1.5-2.0. The irregular characteristic of the analytical curves was interpreted as an increased vapour loss at higher analyte concentrations through the opened ends of the standard THGA tubes. This vapour loss was associated with the significantly diverse expulsion velocities of atoms, caused by the difference in temperature and concentration gradients, when evaporating amounts of analytes with more than one order of magnitude difference.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1039/B208198A
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“Modeling of photon scattering at high X-ray energies : experiment versus simulation”. Vincze L, Vekemans B, Janssens K, Adams F, Journal of analytical atomic spectrometry
T2 –, 15th International Congress on X-Ray Optics and Microanalysis (ICXOM), AUG 24-27, 1998, ANTWERP, BELGIUM 14, 529 (1999). http://doi.org/10.1039/A808040B
Abstract: The use of a detailed Monte Carlo simulation code for X-ray fluorescence spectrometers is demonstrated for calculating the outcome of X-ray scattering experiments in the incident energy range 40-80 keV. The code was validated by comparisons of experimental and simulated spectral distributions in the case of thick, homogeneous samples in which multiple photon scattering occurs with high probability. The experimental spectral distributions were collected at beamline BW5 of HASYLAB, Germany, where a highly energetic, monochromatic synchrotron beam is available. With respect to heterogeneous samples, the code was employed to evaluate the use of Rayleigh and Compton scatter signals for obtaining three dimensional information on the sample dark matrix composition.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
DOI: 10.1039/A808040B
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“Revealing hidden paint layers in oil paintings by means of scanning macro-XRF : a mock-up study based on Rembrandt's “An old man in military costume””. Alfeld M, de Nolf W, Cagno S, Janssens K, et al, Journal of analytical atomic spectrometry 28, 40 (2013). http://doi.org/10.1039/C2JA30119A
Abstract: Over the past several decades the oeuvre of Rembrandt has been the subject of extensive art historical and scientific investigations. One of the most striking features to emerge is his frequent re-use of canvases and panels. The painting An Old Man in Military Costume (78.PB.246), in the collection of the J. Paul Getty Museum, is an example of such a re-used panel. Conventional imaging techniques revealed the presence of a second portrait under the surface portrait, but the details of this hidden portrait have not yet been revealed. Vermilion (HgS) has been identified to have been used nearly exclusively in the flesh tones of the lower painting, suggesting that element-specific XRF imaging might successfully image the hidden portrait. To test this hypothesis, a full-scale mock-up of the painting was created, including a “free impression” of the hidden portrait, reproducing as closely as possible the pigments and paint stratigraphy of the original painting. XRF imaging of the mock-up painting was conducted using three different XRF imaging systems: a mobile X-ray tube based system and two synchrotron-based setups (one equipped with multiple SDDs and one equipped with a Maia detector). The sensitivity, limits of detection and imaging capabilities of each system under the chosen experimental conditions are evaluated and compared. The results indicate that an investigation of the original painting by this method would have an excellent chance of success.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
DOI: 10.1039/C2JA30119A
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“A mobile instrument for in situ scanning macro-XRF investigation of historical paintings”. Alfeld M, Pedroso JV, van Hommes ME, van der Snickt G, Tauber G, Blaas J, Haschke M, Erler K, Dik J, Janssens K, Journal of analytical atomic spectrometry 28, 760 (2013). http://doi.org/10.1039/C3JA30341A
Abstract: Scanning macro-X-ray fluorescence analysis (MA-XRF) is rapidly being established as a technique for the investigation of historical paintings. The elemental distribution images acquired by this method allow for the visualization of hidden paint layers and thus provide insight into the artist's creative process and the painting's conservation history. Due to the lack of a dedicated, commercially available instrument the application of the technique was limited to a few groups that constructed their own instruments. We present the first commercially available XRF scanner for paintings, consisting of an X-ray tube mounted with a Silicon-Drift (SD) detector on a motorized stage to be moved in front of a painting. The scanner is capable of imaging the distribution of the main constituents of surface and sub-surface paint layers in an area of 80 by 60 square centimeters with dwell times below 10 ms and a lateral resolution below 100 mu m. The scanner features for a broad range of elements between Ti (Z = 22) and Mo (Z = 42) a count rate of more than 1000 counts per second (cps)?mass percent and detection limits of 100 ppm for measurements of 1 s duration. Next to a presentation of spectrometric figures of merit, the value of the technique is illustrated through a case study of a painting by Rembrandt's student Govert Flinck (1615-1660).
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 106
DOI: 10.1039/C3JA30341A
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“The effect of the sampling cone position and diameter on the gas flow dynamics in an ICP”. Aghaei M, Lindner H, Bogaerts A, Journal of analytical atomic spectrometry 28, 1485 (2013). http://doi.org/10.1039/c3ja50107h
Abstract: An inductively coupled plasma, connected to a sampling cone of a mass spectrometer, is computationally investigated. The effects of the sampler orifice diameter (ranging from 1 to 2 mm) and distance of the sampler cone from the load coil (ranging from 7 to 17 mm) are studied. An increase in sampler orifice diameter leads to a higher central plasma temperature at the place of the sampler, as well as more efficient gas transfer through the sampler, by reducing the interaction of the plasma gas with the sampling cone. However, the flow velocity at the sampler position is found to be independent of the sampler orifice diameter. Moreover, by changing the sampler orifice diameter, we can control whether only the central gas or also the auxiliary gas can exit through the sampler. Finally, with the increasing distance of the sampler from the load coil, the plasma temperature at the place of the sampler decreases slightly, which might also have consequences for the ion generation and transport through the sampling cone.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.379
Times cited: 14
DOI: 10.1039/c3ja50107h
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“Occurrence of gas flow rotational motion inside the ICP torch : a computational and experimental study”. Aghaei M, Flamigni L, Lindner H, Günther D, Bogaerts A, Journal of analytical atomic spectrometry 29, 249 (2014). http://doi.org/10.1039/c3ja50302j
Abstract: An inductively coupled plasma, connected to the sampling cone of a mass spectrometer, is computationally investigated. The occurrence of rotational motion of the auxiliary and carrier gas flows is studied. The effects of operating parameters, i.e., applied power and gas flow rates, as well as geometrical parameters, i.e., sampler orifice diameter and injector inlet diameter, are investigated. Our calculations predict that at higher applied power the auxiliary and carrier gas flows inside the torch move more forward to the sampling cone, which is validated experimentally for the auxiliary gas flow, by means of an Elan 6000 ICP-MS. Furthermore, an increase of the gas flow rates can also modify the occurrence of rotational motion. This is especially true for the carrier gas flow rate, which has a more pronounced effect to reduce the backward motion than the flow rates of the auxiliary and cooling gas. Moreover, a larger sampler orifice (e.g., 2 mm instead of 1 mm) reduces the backward flow of the auxiliary gas path lines. Finally, according to our model, an injector inlet of 2 mm diameter causes more rotations in the carrier gas flow than an injector inlet diameter of 1.5 mm, which can be avoided again by changing the operating parameters.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.379
Times cited: 21
DOI: 10.1039/c3ja50302j
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“Diffusion- and velocity-driven spatial separation of analytes from single droplets entering an ICP off-axis”. Borovinskaya O, Aghaei M, Flamigni L, Hattendorf B, Tanner M, Bogaerts A, Günther D, Journal of analytical atomic spectrometry 29, 262 (2014). http://doi.org/10.1039/c3ja50307k
Abstract: The reproducible temporal separation of ion signals generated from a single multi-element droplet, observed in previous studies, was investigated in detail in this work using an ICPTOFMS with high temporal resolution. It was shown that the signal peak intensities of individual elements temporally shift relative to each other only for droplets moving through the plasma off-axis. The magnitude of these shifts correlated with the vaporization temperatures of the analytes and depended on the radial position of the droplets as well as on the thermal properties and velocity profiles of the carrier gases of the ICP. The occurrence of the signal shifting was explained by a spatial separation of analytes already present in the vapor phase in the ICP from a yet unvaporized residue of the droplet. This separation is most likely driven by anisotropic diffusion of vaporized analytes towards the plasma axis and a radial velocity gradient. The proposed explanation is supported by modeling of the gas velocities inside the ICP and imaging of the atomic and ionic emissions produced from single droplets, whose patterns were sloping towards the center of the torch. The effects observed in these studies are important not only for the fundamental understanding of analyteplasma interactions but have also a direct impact on the signal intensities and stability.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.379
Times cited: 18
DOI: 10.1039/c3ja50307k
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“Inorganic nitrogen speciation in single micrometer-size particles by laser microprobe mass analysis”. Bruynseels F, Otten P, Van Grieken R, Journal of analytical atomic spectrometry 3, 237 (1988). http://doi.org/10.1039/JA9880300237
Abstract: Individual micrometer-size particles of inorganic nitrogen salts, such as NaNO3, NaNO2, (NH4)2SO4, NH4Cl, NH4NO3 and their mixtures, were analysed in the laser microprobe mass analyser. The cluster-ion distributions of the salts are systematically described and can be used to gain speciation information. The results can be used to study the distribution of the atmospheric aerosol inorganic nitrogen compounds and to investigate their chemical transformations under ambient conditions.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1039/JA9880300237
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“Determination of scandium in high-purity titanium using inductively coupled plasma mass spectrometry and glow discharge mass spectrometry as part of its certification as a reference material”. Held A, Taylor P, Ingelbrecht C, de Bièvre P, Broekaert J, van Straaten M, Gijbels R, Journal of analytical atomic spectrometry 10, 849 (1995). http://doi.org/10.1039/ja9951000849
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.466
Times cited: 6
DOI: 10.1039/ja9951000849
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“Quantitative analysis of iron-rich and other oxide-based samples by means of glow discharge mass spectrometry”. de Gendt S, Schelles W, Van Grieken R, Müller V, Journal of analytical atomic spectrometry 10, 681 (1995). http://doi.org/10.1039/JA9951000681
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1039/JA9951000681
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“Comparison between direct current and radiofrequency glow discharge mass spectrometry for the analysis of oxide-based samples”. de Gendt S, Van Grieken R, Hang W, Harrison WW, Journal of analytical atomic spectrometry 10, 689 (1995). http://doi.org/10.1039/JA9951000689
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1039/JA9951000689
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“A large area full-field EDXRF imaging system based on a THCOBRA gaseous detector”. Silva ALM, Carvalho ML, Janssens K, Veloso JFCA, Journal of analytical atomic spectrometry 30, 343 (2015). http://doi.org/10.1039/C4JA00301B
Abstract: By taking advantage of the attractive features in terms of gain, position and energy resolution of the 2D-THCOBRA detector, a new large area Full-Field X-ray Fluorescence Imaging (FF-XRFI) system for EDXRF imaging applications was developed. The proposed FF-XRFI system has an active area of 10 x 10 cm(2) and can be used to examine macroscopic samples with a moderately good energy resolution (< 1.6 keV FWHM at 8 keV) and a suitable spatial resolution (similar to 500 mu m FWHM). This combination of characteristics allows us to record elemental distribution maps from the surface of different sample types by combining image and energy information. Two different approaches were used for X-ray optics, one based on a single pinhole and another based on a parallel multiple-hole collimator. To illustrate the system capabilities, some sample examples were imaged and studied.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 11
DOI: 10.1039/C4JA00301B
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“Thermodynamic and experimental study of the degradation of the red pigment mercury sulfide”. Radepont M, Coquinot Y, Janssens K, Ezrati J-J, de Nolf W, Cotte M, Journal of analytical atomic spectrometry 30, 599 (2015). http://doi.org/10.1039/C4JA00372A
Abstract: The red pigment mercury sulfide, called cinnabar or vermilion, is well known to suffer from an alteration giving rise to a grey, grey-white or black color at the surface of degraded works of art. This phenomenon can dramatically affect the esthetical value of artworks. This work aims at assessing the factors (light, halides) influencing the instability of red mercury sulfide and understanding (by combining thermodynamic and experimental approaches) the chemical equilibria governing the formation and evolution of the different degradation compounds. From the thermodynamic study of the Hg-S-Cl-H2O system, it was concluded that Hg(0), Hg3S2Cl2, and Hg2Cl2 can be formed from the reaction of alpha-HgS with ClO(g). In the second part, the artificial ageing experiments presented were carried out on model samples following the conditions assessed in the first part, in order to reproduce natural ageing observed on red mercury sulfide. Similarly to degradation compounds detected on original works of art, mercury chlorine compounds such as calomel (Hg2Cl2) and corderoite (alpha-Hg3S2Cl2) were identified on the surface of alpha-HgS model samples, when exposed to light and a sodium hypochlorite solution. Sulfates were detected as well, and more particularly gypsum (CaSO4 center dot 2H(2)O) when Ca was originally present in the model sample. The relationship between color and composition is discussed as well.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 26
DOI: 10.1039/C4JA00372A
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“Full spectral XANES imaging using the Maia detector array as a new tool for the study of the alteration process of chrome yellow pigments in paintings by Vincent van Gogh”. Monico L, Janssens K, Alfeld M, Cotte M, Vanmeert F, Ryan CG, Falkenberg G, Howard DL, Brunetti BG, Miliani C, Journal of analytical atomic spectrometry 30, 613 (2015). http://doi.org/10.1039/C4JA00419A
Abstract: A combination of synchrotron radiation (SR) micro X-ray fluorescence (m-XRF) and XRF mode X-ray absorption near edge structure (XANES) measurements at the Cr K-edge already allowed us to establish that the photo-reduction of chromates to Cr(III) compounds is the cause of darkening of chrome yellow pigments (PbCr1-xSxO4, 0 <= x <= 0.8) in a number of paintings by Vincent van Gogh and in corresponding artificially aged paint models. A silicon drift detector (SDD) was employed to record the Cr-K XRF radiation in these X-ray micro beam-based measurements. However, in view of the limited count rate capabilities and collection solid angle of a single device, m-XRF and m-XANES employing single element SDDs (or similar) are primarily suited for collection of spectral data from individual points. Additionally, collection of XRF maps via point-by-point scanning with relatively long dwell times per point is possible but is usually confined to small areas. The development of the 384 silicon-diode array Maia XRF detector has provided valuable solutions in terms of data acquisition rate, allowing for full spectral (FS) XANES imaging in XRF mode, i.e., where spectroscopic information is available at each pixel in the scanned map. In this paper, the possibilities of SR Cr K-edge FS-XANES imaging in XRF mode using the Maia detector are examined as a new data collection strategy to study the speciation and distribution of alteration products of lead chromate-based pigments in painting materials. The results collected from two micro-samples taken from two Van Gogh paintings and an aged paint model show the possibility to perform FS-XANES imaging in practical time frames (from several minutes to a few hours) by scanning regions of sample sizes of the same order (more than 500 mm). The sensitivity and capabilities of FS-XANES imaging in providing representative chemical speciation information at the microscale (spatial resolution from similar to 2 to 0.6 mm) over the entire scanned area are demonstrated by the identification of Cr(OH) 3, Cr(III) sulfates and/or Cr(III) organometallic compounds in the corresponding phase maps, as alteration products. Comparable Cr-speciation results were obtained by performing equivalent higher spatial resolution SR m-XRF/single-point m-XANES analysis using a more conventional SDD from smaller regions of interest of each sample. Thus, large-area XRF mode FS-XANES imaging (Maia detector) is here proposed as a valuable and complementary data collection strategy in relation to “ zoomed-in” high-resolution m-XRF mapping and single-point m-XANES analysis (SDD).
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 28
DOI: 10.1039/C4JA00419A
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“Micro-XANES study on Mn browning: use of quantitative valence state maps”. Nuyts G, Cagno S, Bugani S, Janssens K, Journal of analytical atomic spectrometry 30, 642 (2015). http://doi.org/10.1039/C4JA00386A
Abstract: Historical glass, especially non-durable medieval glass, can undergo corrosion. This sometimes results in the formation of dark-coloured manganese-rich inclusions that reduce the transparency of the glass. While unaltered bulk glass contains manganese mainly present in the +II valence state, inside the inclusions Mn is present in higher valence states (+III to +IV). Two different strategies may be considered by conservators when aiming to improve the transparency. One is based on the reduction of highly oxidised black/brown compounds using mildly reducing solutions, while the other focuses more on the extraction of manganese from the inclusions by the application of chelating agents. In this paper, a method for quantitative mapping of the Mn speciation inside partially corroded historical windowpanes based on X-Ray Absorption Near-Edge Structure (XANES) spectroscopy is discussed. The calibration of such Mn valence state maps based on the combo method, a fairly reliable way to determine the oxidation state, is described in more detail. This method is used to evaluate the effect of reducing treatments on historical glass, dated to the 14th century and originating from Sidney Sussex College (Cambridge, UK), suffering from Mn browning. Glasses were examined by means of Synchrotron Radiation (SR) based microscopic X-Ray Absorption Near-Edge Structure (mXANES) spectroscopy and microscopic X-Ray Fluorescence (mXRF). X-Ray elemental distribution maps of glass cross-sections are recorded at different energies, while Mn K-edge spectra are used to convert these into Mn valence state (VS) maps. Such valence state maps will allow evaluation of a reducing treatment.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 8
DOI: 10.1039/C4JA00386A
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“Strategies for processing mega-pixel X-ray fluorescence hyperspectral data: a case study on a version of Caravaggio's painting Supper at Emmaus”. Alfeld M, Janssens K, Journal of analytical atomic spectrometry 30, 777 (2015). http://doi.org/10.1039/C4JA00387J
Abstract: Technical progress in the fields of X-ray sources, optics and detectors is constantly enhancing the pace of data acquisition in XRF imaging. This enlarges the size of the hyperspectral datasets and the number of their sub-parts. This paper describes the challenges in processing large XRF datasets featuring several million pixels/spectra and the strategies developed to overcome them. During the investigation of historical paintings by scanning macro-XRF the main challenges are the correct identification of all spectral features in a dataset and its timely processing. For the identification of spectral features different approaches are discussed, i.e. the use of sum spectra, maximum pixel spectra and of chi(2)(r) maps. For the time-efficient, artefact-free evaluation of XRF imaging data, different software packages are evaluated and intercompared (AXIL, PyMCA, GeoPIXE and the in-house written datamuncher). The process of data evaluation is illustrated on a large dataset (3.4 MPixels) acquired during the investigation of a version of Caravaggio's Supper at Emmaus (143 x 199.5 cm(2)). This 17th century painting is currently the largest object entirely scanned with macroscopic XRF.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 67
DOI: 10.1039/C4JA00387J
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“Synchrotron-based X-ray spectromicroscopy and electron paramagnetic resonance spectroscopy to investigate the redox properties of lead chromate pigments under the effect of visible light”. Monico L, Janssens K, Cotte M, Romani A, Sorace L, Grazia C, Brunetti BG, Miliani C, Journal of analytical atomic spectrometry 30, 1500 (2015). http://doi.org/10.1039/C5JA00091B
Abstract: Light-induced redox processes have been established as the cause of the chromatic alterations of a number of artists' pigments used from the 15th to the 20th century. Despite the fact that a general comprehension of the mechanisms has been provided through the characterization of photo-degraded compounds, both exhaustive information on the wavelength-dependence of the alteration process of the pigments and experimental evidence in how visible light may influence the formation pathways of specific secondary compounds are still lacking. Establishing an analytical protocol for the study of wavelength-dependence of pigments on photo-redox pathways is relevant for the safe illumination of paintings, especially in view of the possible use of spectrally tunable light sources such as white light emitting diodes (WLEDs). In this work, we propose an integrated approach based on a combination of diffuse reflectance UV-visible, synchrotron radiation (SR)-based micro X-ray fluorescence (m-XRF)/X-ray absorption near edge structure (m-XANES) and electron paramagnetic resonance (EPR) spectroscopies to study the photo-redox process of Cr(VI) -> Cr(III) for lead chromate yellows (PbCr1-xSxO4, 0 <= x <= 0.8) under exposure to different monochromatic light. In view of the thin (3-5 mm) alteration layer that is formed at the paint surface after light exposure, SR-based Cr K-edge mu-XANES/mu-XRF analysis was employed to obtain information on the abundance, nature and distribution of the alteration of Cr(III)-compounds at the micrometricscale level. On the other hand, EPR spectroscopy was used as a complementary tool to the SR-based X-ray methods due to its sensitivity for revealing species containing one or more unpaired electrons and for distinguishing different coordination geometries of paramagnetic centers, such as Cr(V)-species. Semi-quantitative indications about the darkening of the paint surface were obtained by UV-Vis spectroscopy. An abundance of reduced Cr down to around 50% was detected at the aged surface of chrome yellow paints. The reduction process was favored not only by wavelengths shorter than 460 nm (i.e., where the pigment shows its maximum absorption) but also by light in the 490-530 nm range. The first evidence of the presence of Cr(V)-intermediates in the Cr(VI) -> Cr(III) reduction reaction allowed the risks of inducing photo-degradation of the 490-530 nm wavelength range to be explained.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 17
DOI: 10.1039/C5JA00091B
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“Iron speciation in soda-lime-silica glass: a comparison of XANES and UV-vis-NIR spectroscopy”. Ceglia A, Nuyts G, Meulebroeck W, Cagno S, Silvestri A, Zoleo A, Nys K, Janssens K, Thienpont H, Terryn H, Journal of analytical atomic spectrometry 30, 1552 (2015). http://doi.org/10.1039/C5JA00046G
Abstract: Scientific analyses of ancient glasses have been carried out for many years using elemental chemical analysis. However, it is known that the control of the redox conditions in the glass melt has a strong implication on the final hue of glass because it affects Fe2+/SFe. Therefore an increasing number of studies on the redox conditions have been published in recent years by means of synchrotron based Xray absorption spectroscopy. This is a technique which is not easily accessible and requires dedicated facilities. In this paper we describe an alternative approach by means of optical absorption spectroscopy. We synthesised 10 soda-lime-silica glasses with known redox conditions and iron concentration to calibrate the absorption at 1100 nm as a function of Fe2+ concentration. The linear extinction coefficient was also determined. These glasses were also studied by means of X-ray Absorption Near Edge Structure (XANES) spectroscopy. Electron paramagnetic resonance spectroscopy was additionally used as an ancillary method to verify the quality of our data. Furthermore 28 samples from real archaeological samples were analysed by XANES and optical spectroscopy as a case study. The Fe2+/SFe values obtained were compared and demonstrated that the two techniques were in good agreement with each other. Optical spectroscopy can be applied in situ with moderate sample preparation to determine the concentration of Fe2+. To investigate the redox conditions, especially as a first screening approach, this methodology is an important tool to take into consideration before applying more sophisticated techniques such as XANES, which is more elaborate and requires high-tech resources.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 20
DOI: 10.1039/C5JA00046G
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“Particle transport through an inductively coupled plasma torch: elemental droplet evaporation”. Aghaei M, Bogaerts A, Journal of analytical atomic spectrometry 31, 631 (2016). http://doi.org/10.1039/C5JA00162E
Abstract: We studied the transport of copper droplets through an inductively coupled plasma, connected to the sampling cone of a mass spectrometer, by means of a computational model. The sample droplets are followed until they become evaporated. They are inserted as liquid particles from the central inlet and the effects of injection position (i.e. “on” and “off” axis), droplet diameter, as well as mass loading flow rate are investigated. It is shown that more “on-axis” injection of the droplets leads to a more straight path line, so that the droplets move less in the radial direction and are evaporated more on the central axis, enabling a better sample transfer efficiency to the sampler cone. Furthermore, there are optimum ranges of diameters and flow rates, which guarantee the proper position of evaporation along the torch, i.e. not too early, so that the sample can get lost in the torch, and not too late, which reduces the chance of becoming ionized before reaching the sampler.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.379
Times cited: 21
DOI: 10.1039/C5JA00162E
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“Visualization of As(III) and As(V) distributions in degraded paint micro-samples from Baroque- and Rococo-era paintings”. Vermeulen M, Nuyts G, Sanyova J, Vila A, Buti D, Suuronen J-P, Janssens K, Journal of analytical atomic spectrometry 31, 1913 (2016). http://doi.org/10.1039/C6JA00134C
Abstract: Orpiment and realgar, both arsenic sulfide pigments respectively used for their vivid yellow and red-orange hues, are two of many artists' pigments that appear not to be stable upon light exposure, quickly degrading to arsenic trioxide and arsenate. This often results in whitening or transparency in the painted surfaces. While conventional techniques such as microscopic Raman (mu-RS) and microscopic Fourier transform infrared (mu-FTIR) spectroscopies can allow a quick and relatively easy identification of the orpiment, realgar, artificial arsenic sulfide glass and, to some extent, arsenic oxide, the identification and visualization of distributions of the degradation products – and especially arsenate compounds – in the paint micro-samples is generally more challenging. This challenge is due to the rather unfavorable limit of detection and low spectral resolution of such conventional spectroscopic techniques. This restricts the conclusions that can be drawn regarding the conservation state of valuable works of art. In this paper, we present how synchrotron radiation (SR) based techniques can overcome this challenge while working on painting cross-sections taken from a 17th-century painting by the Flemish artist Daniel Seghers (oil on canvas, Statens Museum for Kunst, Denmark) and an 18th-century French Chinoiserie (private collection, France). SR micro-X-ray fluorescence (m-XRF) mapping analysis performed on a visually degraded orpiment-containing paint stratigraphy reveals that arsenic is distributed throughout the entire cross-section, while X-ray absorption near edge structure (mu-XANES) demonstrated that the arsenic is present in both arsenite (As-III) and arsenate (As-V) forms. The latter compound(s), despite being barely identifiable by means of FTIR, were not only located at the surface of large and partially altered grains of arsenic sulfide but also spread throughout the entire paint stratigraphy. Their presence and distribution are attributed either to the complete degradation of smaller arsenic sulfide grains or to migration of the arsenates within the paint layer away from their original location of formation. The combination of mu-XRF and mu-XANES was very useful for the characterization of the advanced degradation state of the arsenic-containing pigments in paint systems; this type of information could not be obtained by means of conventional spectroscopic methods of microanalysis.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 20
DOI: 10.1039/C6JA00134C
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“Inductively coupled plasma-mass spectrometry: insights through computer modeling”. Bogaerts A, Aghaei M, Journal of analytical atomic spectrometry 32, 233 (2017). http://doi.org/10.1039/C6JA00408C
Abstract: In this tutorial review paper, we illustrate how computer modeling can contribute to a better insight in inductively coupled plasma-mass spectrometry (ICP-MS). We start with a brief overview on previous efforts, studying the fundamentals of the ICP and ICP-MS, with main focus on previous modeling activities. Subsequently, we explain in detail the model that we developed in previous years, and we show typical calculation results, illustrating the plasma characteristics, gas flow patterns and the sample transport, evaporation and ionization. We also present the effect of various experimental parameters, such as operating conditions, geometrical aspects and sample characteristics, to illustrate how modeling can help to elucidate the optimal conditions for improved analytical performance.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.379
Times cited: 14
DOI: 10.1039/C6JA00408C
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“The ID21 X-ray and infrared microscopy beamline at the ESRF: status and recent applications to artistic materials”. Cotte M, Pouyet E, Salome M, Rivard C, De Nolf W, Castillo-Michel H, Fabris T, Monico L, Janssens K, Wang T, Sciau P, Verger L, Cormier L, Dargaud O, Brun E, Bugnazet D, Fayard B, Hesse B, del Real AEP, Veronesi G, Langlois J, Balcar N, Vandenberghe Y, Sole VA, Kieffer J, Barrett R, Cohen C, Cornu C, Baker R, Gagliardini E, Papillon E, Susini J, Journal of analytical atomic spectrometry 32, 477 (2017). http://doi.org/10.1039/C6JA00356G
Abstract: The ID21 beamline (European Synchrotron Radiation facility, France) is a multi micro-analytical platform combining X-ray and infrared micro-probes, for characterization of elements, species, molecular groups and crystalline structures in complex materials. Applications are mainly in the fields of cultural heritage, life science, environmental and earth sciences, materials sciences. Here, we first present the status of instruments: (i) the scanning micro-spectroscopy end-station, operating from 2.0 to 9.2 keV, under vacuum and offering cryo conditions, for the acquisition of 2D micro X-ray fluorescence (mu XRF) maps, single point micro X-ray Absorption Near Edge Structure (mu XANES) spectra and speciation maps with sub-micrometric resolution; (ii) the XANES full-field end-station, operating in the same vacuum and energy conditions, for the acquisition of hyper-spectral radiographs of thin concentrated samples, resulting in speciation maps with micrometric resolution and millimetric field of view; (iii) the scanning micro-X-ray diffraction (mu XRD)/mu XRF end-station, operating at 8.5 keV, in air, for the acquisition of 2D crystalline phase maps, with micrometric resolution; and (iv) the scanning infrared microscope, operating in the mid-infrared range for the acquisition of molecular maps and some structural maps with micrometric resolution. Recent hardware and software developments are presented, as well as new protocols for improved sample preparation of thin sections. Secondly, a review of recent applications for the study of cultural heritage is presented, illustrated by various examples: determination of the origin of the color in blue Chinese porcelains and in brown Sevres porcelains; detection of lead in ink on Herculaneum papyri; identification and degradation of modeling materials used by Auguste Rodin and of chrome yellow pigments used by Vincent van Gogh. Cryo capabilities are illustrated by the analysis of plants exposed to chromate solutions. These examples show the variety of materials analyzed, of questions tackled, and particularly the multiple advantages of the ID21 analytical platform for the analysis of ancient and artistic materials.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 39
DOI: 10.1039/C6JA00356G
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“The darkening of copper- or lead-based pigments explained by a structural modification of natural orpiment : a spectroscopic and electrochemical study”. Vermeulen M, Sanyova J, Janssens K, Nuyts G, De Meyer S, De Wael K, Journal of analytical atomic spectrometry 32, 1331 (2017). http://doi.org/10.1039/C7JA00047B
Abstract: A combined Raman and electrochemical study of natural orpiment (As2S3), an arsenic sulfide pigment, was used to assess the quick formation of oxidized species such as arsenic oxide (As2O3) upon exposing the pigment to 405 nm or 532 nm monochromatic light while simultaneously recording the Raman spectra of the exposed sample. During this process, a distortion of the main band at 355 cm−1, associated with the stretching of the AsS3/2 pyramids of natural orpiment, was observed as well as an increased intensity of the 359 cm−1 band, corresponding to covalent AsAs bonds in natural orpiment. The distortion was accompanied by an overall decrease of the global Raman signal for natural orpiment, which could be explained by a loss in the crystal structure. The same phenomena were recorded in reference natural orpiment model paint samples stored for a long time together with verdigris (Cu(OH)2·(CH3COO)2·5H2O) and minium (Pb3O4) paints, the latter two appearing darkened on their sides closest to the orpiment sample as well as in several historical samples containing natural orpiment mixed with various blue pigments. By SEM-EDX and XRPD analysis, respectively on loose material and cast thin-sections of model paint samples, the darkening was identified as dark sulfide species such as chalcocite (Cu2S) and galena (PbS), suggesting the release of volatile sulfide or related species by the natural orpiment paint. XANES analyses of paint samples presenting AsAs bond increase indicated the presence of sulfur species most likely identified as organosulfur compounds formed upon the AsAs bond formation and explained the darkening of the Cu- and Pb-based pigments. To the best of our knowledge, this article reports for the first time the light-induced formation of AsAs bonds in natural orpiment used as an artists' pigment and objectively demonstrates the incompatibility between orpiment and (arsenic) sulfide-sensitive pigments.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
Times cited: 10
DOI: 10.1039/C7JA00047B
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“Combined 1D, 2D and 3D micro-XRF techniques for the analysis of illuminated manuscripts”. Lachmann T, van der Snickt G, Haschke M, Mantouvalou I, Journal of analytical atomic spectrometry 31, 1989 (2016). http://doi.org/10.1039/C6JA00220J
Abstract: The combination of several micro-XRF analysis modes is presented for the investigation of an illuminated parchment manuscript. With a commercial instrument, conventional micro-XRF spot analysis (0D) and mapping (2D) are performed, yielding detailed lateral elemental information. Depth resolution becomes accessible by mounting an additional polycapillary lens in front of an SDD detector. Quantitative confocal depth profiles (1D) are presented as well as the full separation of the front and the backside decorations with the help of fast 3D mappings of specific areas. Only through the use of these multidimensional modes can elemental information be assigned both to lateral and depth positions, making the analysis of such heterogeneous samples feasible.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1039/C6JA00220J
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“Optimization of secondary cathode thickness for direct current glow discharge mass spectrometric analysis of glass”. Schelles W, de Gendt S, Van Grieken RE, Journal of analytical atomic spectrometry 11, 937 (1996). http://doi.org/10.1039/JA9961100937
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1039/JA9961100937
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“Relative sensitivity factors in glow discharge mass spectrometry: the role of charge transfer ionization”. Bogaerts A, Gijbels R, Journal of analytical atomic spectrometry 11, 841 (1996). http://doi.org/10.1039/ja9961100841
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.466
Times cited: 38
DOI: 10.1039/ja9961100841
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“Micro and surface analysis in archaeology”. Adams F, Adriaens A, Aerts A, de Raedt I, Janssens K, Schalm O, Journal of analytical atomic spectrometry 12, 257 (1997). http://doi.org/10.1039/A606091I
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
DOI: 10.1039/A606091I
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“Quantification of boron in cells for evaluation of drug agents used in boron neutron capture therapy”. Verlinden B, Van Hoecke K, Aerts A, Daems N, Dobney A, Janssens K, Cardinaels T, Journal Of Analytical Atomic Spectrometry 36, 598 (2021). http://doi.org/10.1039/D0JA00456A
Abstract: Boron neutron capture therapy (BNCT) is an extensively studied radiotherapeutic strategy for cancer treatment. BNCT is based on irradiation of malignant tumour cells with neutrons after uptake of a B-10 containing molecule. Alpha particles, locally produced by neutron irradiation kill the cancer cells. Important for ongoing research regarding cellular uptake and cytotoxicity of a large variety of B-10 containing molecules is the accurate determination of boron concentrations in cell cultures. In this work, the sample preparation for quantitative inductively coupled plasma mass spectrometry (ICP-MS) analysis on cell cultures was optimized. By making use of acid digestion combined with UV digestion, low detection limits (0.4 mu g L-1) and full recoveries of boron could be achieved while measurements were free of spectral and non-spectral interferences. Finally, cell-associated boron in the form of 4-borono-l-phenylalanine (l-BPA) in vascular endothelial cell cultures could be determined with ICP-MS as (1.26 +/- 0.10) x 10(9) boron atoms per cell. The developed method can prove its importance for further BNCT research and elemental analysis of cell cultures.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.379
DOI: 10.1039/D0JA00456A
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