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“Aptasensing of chloramphenicol in the presence of its analogues : reaching the maximum residue limit”. Pilehvar S, Mehta J, Dardenne F, Robbens J, Blust R, De Wael K, Analytical chemistry 84, 6753 (2012). http://doi.org/10.1021/AC3012522
Abstract: A novel label-free folding induced aptamer-based electrochemical biosensor for the detection of chloramphenicol (CAP) in the presence of its analogues has been developed. CAP is a broad-spectrum antibiotic which has lost its favor due to its serious adverse toxic effects on human health. Aptamers are artificial nucleic acid ligands (ssDNA or RNA) able to specifically recognize a target such as CAP. In this article, the aptamers are fixed onto a gold electrode surface by a self-assembly approach. In the presence of CAP, the unfolded ssDNA on the electrode surface changes to a hairpin structure bringing the target molecules close to the surface and trigger electron transfer. Detection limits were determined to be 1.6×10-9 mol L-1. In addition, thiamphenicol (TAP) and florfenicol (FF), antibiotics with a similar structure to CAP, did not influence the performance of the aptasensor, suggesting a good selectivity of the CAP-aptasensor. Simplicity and lower detection limit (because of the home-selected aptamers) make that the electrochemical aptasensor is suitable for practical use in the detection of CAP in milk samples.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 68
DOI: 10.1021/AC3012522
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“The use of potentiometric sensors to study (bio)molecular interactions”. De Wael K, Daems D, Van Camp G, Nagels LJ, Analytical chemistry 84, 4921 (2012). http://doi.org/10.1021/AC3005428
Abstract: Potentiometric sensors were used to study molecular interactions in liquid environments, with sensorgram methodology. This is demonstrated with a lipophilic rubber-, and with a collagen based hydrogel sensor coating. The investigated molecules were promazine and tartaric acid respectively. The sensors were placed in a hydrodynamic wall jet system for the recording of sensorgrams. mV sensor responses were first converted to a signal, expressing the concentration of adsorbed organic ions. Using a linearization method, a pseudo first order kinetic model of adsorption was shown to fit the experimental results perfectly. Kass, kon and koff values were calculated.. The technique can be used over 4 decades of concentration, and it is very sensitive to low MW compounds as well as to multiply charged large biomolecules. This study is the first to demonstrate the application of potentiometric sensors as an alternative and complement to SPR methods.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 10
DOI: 10.1021/AC3005428
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“Possibilities of energy-resolved X-ray radiography for the investigation of paintings”. Cabal Rodríguez AE, Leyva Pernia D, Schalm O, van Espen PJM, Analytical and bioanalytical chemistry 402, 1471 (2012). http://doi.org/10.1007/S00216-011-5230-X
Abstract: X-ray radiographic images of paintings often show little or no contrast. In order to increase the contrast in radiographic images we measured the X-ray spectrum of a low power X-ray tube, after passing through the painting, with a high energy-resolution SDD detector. To obtain images, the detector is collimated with a 400 mu m diameter pinhole and the painting was moved through the beam in the x and y-direction using a dwell time of a few seconds per pixel. The data obtained consists of a data cube of, typically, 200 x 200 pixels and a 512-channel X-ray spectrum for each pixel, spanning the energy range from 0 to 40 keV. Having the absorbance spectrum available for each pixel, we are able, a posteriori, to produce images by edge subtraction for any given element. In this way high contrast, element-specific, images can be obtained. Because of the high energy-resolution a much simpler edge subtraction algorithm can be applied. We also used principal-component imaging to obtain, in a more automated way, images with high contrast. Some of these images can easily be attributed to specific elements. It turns out that preprocessing of the spectral data is crucial for the success of the multivariate image processing.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1007/S00216-011-5230-X
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“Characterization of aerosol-associated lead by DPASV and LAMMA”. Wonders JHAM, Houweling S, de Bont FAJ, van Leeuwen HP, Eeckhaoudt SM, Van Grieken R, International journal of environmental analytical chemistry 56, 193 (1994). http://doi.org/10.1080/03067319408034100
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1080/03067319408034100
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“FIB, TEM and LA-ICPMS investigations on melt inclusions in Martian meteorites –, Analytical capabilities and geochemical insights”. Bleiner D, Macri M, Gasser P, Sautter V, Maras A, Talanta : the international journal of pure and applied analytical chemistry (2006). http://doi.org/10.1016/J.TALANTA.2005.08.022
Abstract: In order to obtain full information coverage on melt inclusions in Martian meteorites (subgroup nakhlites) complementary micro-analytical techniques were used, i.e. focused ion beam, transmission electron microscopy and laser ablation. Using focused ion beam several lamellae for transmission electron microscopy were prepared and secondary electron images of cross-sections could be acquired. Laser ablation-inductively coupled plasma mass spectrometry analyses were performed on selected inclusions to obtain mass-oriented bulk composition of inclusions at depth. The differences in composition between melt inclusions in olivine and augite crystals would suggest a xenocrystic origin for olivine. Furthermore, electron diffraction patterns clearly indicated that the SiO2-rich phase in inclusions from augite in meteorites from Northwest Africa site is re-crystallized, whereas it is still vitreous in the inclusions from Nakhla sampling site. Therefore, different post-entrapment evolutions were active for the two nakhlite meteorite sets, the Nakhla and the NWA817 set. Melt inclusions in Nakhla olivine presented alteration veins, which were presumably produced before their landing on Earth. If this is the case, this would indicate a alteration stage already on Mars with all the consequence in terms of climate history. Melt inclusions in Nakhla augite resulted unaffected by any alteration or modification following the entrapment, and therefore represent the best candidate to indicate the pristine magma composition. (c) 2005 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.162
Times cited: 9
DOI: 10.1016/J.TALANTA.2005.08.022
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“Quantitative characterization of individual particle surfaces by fractal analysis of scanning electron microscope images”. van Put A, Vertes A, Wegrzynek D, Treiger B, Van Grieken R, Fresenius' journal of analytical chemistry 350, 440 (1994). http://doi.org/10.1007/BF00321787
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1007/BF00321787
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“Study on the impregnation of archaeological waterlogged wood with consolidation treatments using synchrotron radiation microtomography”. Bugani S, Modugno F, Lucejko JJ, Giachi G, Cagno S, Cloetens P, Janssens K, Morselli L, Analytical and bioanalytical chemistry 395, 1977 (2009). http://doi.org/10.1007/S00216-009-3101-5
Abstract: In favourable conditions of low temperature and low oxygen concentration, archaeological waterlogged wooden artefacts, such as shipwrecks, can survive with a good state of preservation. Nevertheless, anaerobic bacteria can considerably degrade waterlogged wooden objects with a significant loss in polysaccharidic components. Due to these decay processes, wood porosity and water content increase under ageing. In such conditions, the conservation treatments of archaeological wooden artefacts often involve the replacement of water with substances which fill the cavities and help to prevent collapse and stress during drying. The treatments are very often expensive and technically difficult, and their effectiveness very much depends on the chemical and physical characteristics of the substances used for impregnation. Also important are the degree of cavity-filling, penetration depth and distribution in the structure of the wood. In this study, the distribution in wood cavities of some mixtures based on polyethylene glycols and colophony, used for the conservation of waterlogged archaeological wood, was investigated using synchrotron radiation X-ray computed microtomography (SR-A mu CT). This non-destructive imaging technique was useful for the study of the degraded waterlogged wood and enabled us to visualise the morphology of the wood and the distribution of the materials used in the wood treatments. The study has shown how deposition is strictly related to the dimension of the wooden cavities. The work is currently proceeding with the comparison of synchrotron observations with the data of the solutions viscosity and with those of the properties imparted to the wood by the treatments.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.431
Times cited: 30
DOI: 10.1007/S00216-009-3101-5
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“Simulation and experimental studies on plasma temperature, flow velocity, and injector diameter effects for an inductively coupled plasma”. Lindner H, Murtazin A, Groh S, Niemax K, Bogaerts A, Analytical chemistry 83, 9260 (2011). http://doi.org/10.1021/ac201699q
Abstract: An inductively coupled plasma (ICP) is analyzed by means of experiments and numerical simulation. Important plasma properties are analyzed, namely, the effective temperature inside the central channel and the mean flow velocity inside the plasma. Furthermore, the effect of torches with different injector diameters is studied by the model. The temperature inside the central channel is determined from the end-on collected line-to-background ratio in dependence of the injector gas flow rates. Within the limits of 3% deviation, the results of the simulation and the experiments are in good agreement in the range of flow rates relevant for the analysis of relatively large droplets, i.e., 50 μm. The deviation increases for higher gas flow rates but stays below 6% for all flow rates studied. The velocity of the gas inside the coil region was determined by side-on analyte emission measurements with single monodisperse droplet introduction and by the analysis of the injector gas path lines in the simulation. In the downstream region significantly higher velocities were found than in the upstream region in both the simulation and the experiment. The quantitative values show good agreement in the downstream region. In the upstream region, deviations were found in the absolute values which can be attributed to the flow conditions in that region and because the methods used for velocity determination are not fully consistent. Eddy structures are found in the simulated flow lines. These affect strongly the way taken by the path lines of the injector gas and they can explain the very long analytical signals found in the experiments at low flow rates. Simulations were performed for different injector diameters in order to find conditions where good analyte transport and optimum signals can be expected. The results clearly show the existence of a transition flow rate which marks the lower limit for effective analyte transport conditions through the plasma. A rule-of-thumb equation was extracted from the results from which the transition flow rate can be estimated for different injector diameters and different injector gas compositions.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 34
DOI: 10.1021/ac201699q
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“Compositional and quantitative microtextural characterization of historic paintings by micro-X-ray diffraction and Raman microscopy”. Romero-Pastor J, Duran A, Rodríguez-Navarro AB, Van Grieken R, Cardell C, Analytical chemistry 83, 8420 (2011). http://doi.org/10.1021/AC201159E
Abstract: This work shows the benefits of characterizing historic paintings via compositional and microtextural data from micro-X-ray diffraction (μ-XRD) combined with molecular information acquired with Raman microscopy (RM) along depth profiles in paint stratigraphies. The novel approach was applied to identify inorganic and organic components from paintings placed at the 14th century Islamic UniversityMadrasah Yusufiyyain Granada (Spain), the only Islamic University still standing from the time of Al-Andalus (Islamic Spain). The use of μ-XRD to obtain quantitative microtextural information of crystalline phases provided by two-dimensional diffraction patterns to recognize pigments nature and manufacture, and decay processes in complex paint cross sections, has not been reported yet. A simple Nasrid (14th century) palette made of gypsum, vermilion, and azurite mixed with glue was identified in polychromed stuccos. Here also a Christian intervention was found via the use of smalt, barite, hematite, Brunswick green and gold; oil was the binding media employed. On mural paintings and wood ceilings, more complex palettes dated to the 19th century were found, made of gypsum, anhydrite, barite, dolomite, calcite, lead white, hematite, minium, synthetic ultramarine blue, and black carbon. The identified binders were glue, egg yolk, and oil.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1021/AC201159E
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“Optimization of the ion chromatographic quantification of airborne fluoride, acetate and formate in the Metropolitan Museum of Art, New York”. Kontozova-Deutsch V, Deutsch F, Bencs L, Krata A, Van Grieken R, De Wael K, Talanta : the international journal of pure and applied analytical chemistry 86, 372 (2011). http://doi.org/10.1016/J.TALANTA.2011.09.030
Abstract: Ion chromatographic (IC) methods have been compared in order to achieve an optimal separation of fluoride, acetate and formate under various elution conditions on two formerly introduced analytical columns (i and ii) and a novel one (iii): (i) an IonPac AS14 (250 mm × 4 mm I.D.), (ii) Allsep A-2 (150 mm × 4.6 mm I.D.), and (iii) an IC SI-50 4E (250 mm (length) × 4 mm (internal diameter – I.D.)). The IC conditions for the separation of the anions concerned were optimized on the IC SI-50 4E column. A near baseline separation of these anions was attained on the IonPac AS14, whereas the peaks of fluoride and acetate could not be resolved on the Allsep A-2. A baseline separation for the three anions was achieved on the IC SI-50 4E column, when applying an eluent mixture of 3.2 mmol/L Na2CO3 and 1.0 mmol/L NaHCO3 with a flow rate of 1.0 mL/min. The highest precision of 1.7, 3.0 and 2.8% and the best limits of detection (LODs) of 0.014, 0.22 and 0.17 mg/L for fluoride, acetate and formate, respectively, were obtained with the IC SI-50 4E column. Hence, this column was applied for the determination of the acetic and formic acid contents of air samples taken by means of passive gaseous sampling at the Metropolitan Museum of Art in New York, USA. Atmospheric concentrations of acetic and formic acid up to 1050 and 450 μg/m3, respectively, were found in non-aerated showcases of the museum. In galleries and outdoors, rather low levels of acetic and formic acid were detected with average concentrations of 50 and 10 μg/m3, respectively. The LOD data of acetate and formate on the IC SI-50 4E column correspond to around 0.5 μg/m3 for both acetic and formic acid in air samples.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.162
Times cited: 19
DOI: 10.1016/J.TALANTA.2011.09.030
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“Fast heating induced impulse halogenation of refractory sample components in electrothermal atomic absorption spectrometry by direct injection of a liquid halogenating agent”. György K, Ajtony Z, van Meel K, Van Grieken R, Czitrovszky A, Bencs L, Talanta : the international journal of pure and applied analytical chemistry 85, 1253 (2011). http://doi.org/10.1016/J.TALANTA.2011.05.028
Abstract: A novel electrothermal atomic absorption spectrometry (ETAAS) method was developed for the halogenation of refractory sample components (Er, Nd and Nb) of lithium niobate (LiNbO3) and bismuth tellurite (Bi2TeO5) optical single crystals to overcome memory effects and carry-over. For this purpose, the cleaning step of a regular graphite furnace heating program was replaced with a halogenation cycle. In this cycle, after the graphite tube cooled to room temperature, a 20 μL aliquot of liquid carbon tetrachloride (CCl4) was dispensed with a conventional autosampler into the graphite tube. The CCl4 was partially dried at 80 °C under the mini-flow (40 cm3 min−1) condition of the Ar internal furnace gas (IFG), then the residue was decomposed (pyrolyzed) by fast furnace heating at 19002100 °C under interrupted flow of the IFG. This step was followed by a clean-out stage at 2100 °C under the maximum flow of the IFG. The advantage of the present method is that it does not require any alteration to the graphite furnace gas supply system in contrast to most of the formerly introduced halogenation techniques. The effectiveness of the halogenation method was verified with the determination of Er and Nd dopants in the optical crystals. In these analyses, a sensitivity decrease was observed, which was likely due to the enhanced deterioration of the graphite tube surface. Therefore, the application of mathematical correction (resloping) of the calibration was also required. The calibration curves were linear up to 1.5 and 10 μmol L−1 for Er and Nd, respectively. Characteristic masses of 18 and 241 pg and the limit of detection (LOD) values of 0.017 and 0.27 μmol L−1 were found for Er and Nd, respectively. These LOD data correspond to 0.68 μmol mol−1 Er and 11 μmol mol−1 Nd in solid bismuth tellurite samples. The analytical results were compared with those obtained by a conventional ETAAS method and validated with X-ray fluorescence spectrometry analysis.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.TALANTA.2011.05.028
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“Room-temperature study of iron gall ink impregnated paper degradation under various oxygen and humidity conditions : time-dependent monitoring by viscosity and X-ray absorption near-edge spectrometry measurements”. Rouchon V, Duranton M, Burgaud C, Pellizzi E, Lavédrine B, Janssens K, de Nolf W, Nuyts G, Vanmeert F, Hellemans K, Analytical chemistry 83, 2589 (2011). http://doi.org/10.1021/AC1029242
Abstract: Many western manuscripts were written using iron gall inks. These inks can damage the paper via two major mechanisms: (a) acid hydrolysis, enhanced by humidity, and (b) oxidative depolymerization provoked by the presence of oxygen and free iron(II) ions. The degradation of unsized Whatman paper impregnated with different combinations of iron sulfate, gallic acid, and gum arabic was studied at room temperature in order to assess the relative importance of each mechanism. The samples were stored in various environments including a dry and/or an oxygen-free atmosphere. The cellulose depolymerization was monitored by viscometry and related to changes in the oxidation state of iron, determined by X-ray absorption near-edge spectrometry. The results indicate that residual amounts of oxygen (less than 0.1%) promote cellulose depolymerization, whereas the level of relative humidity has no impact. The cellulose depolymerization also appears closely correlated to oxidative mechanisms. Regarding the oxidation of iron, it only occurs in the simultaneous presence of oxygen and moisture, suggesting the occurrence of rustlike oxidative mechanisms. Finally, the presence of gallic acid has a strong influence, which is only partially explained by its capacity to reduce iron(III) to iron(II).
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 28
DOI: 10.1021/AC1029242
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods : 2 : original paint layer samples”. Monico L, van der Snickt G, Janssens K, de Nolf W, Miliani C, Dik J, Radepont M, Hendriks E, Geldof M, Cotte M, Analytical chemistry 83, 1224 (2011). http://doi.org/10.1021/AC1025122
Abstract: The darkening of the original yellow areas painted with the chrome yellow pigment (PbCrO4, PbCrO4·xPbSO4, or PbCrO4·xPbO) is a phenomenon widely observed on several paintings by Vincent van Gogh, such as the famous different versions of Sunflowers. During our previous investigations on artificially aged model samples of lead chromate, we established for the first time that darkening of chrome yellow is caused by reduction of PbCrO4 to Cr2O3·2H2O (viridian green), likely accompanied by the presence of another Cr(III) compound, such as either Cr2(SO4)3·H2O or (CH3CO2)7Cr3(OH)2 [chromium(III) acetate hydroxide]. In the second part of this work, in order to demonstrate that this reduction phenomenon effectively takes place in real paintings, we study original paint samples from two paintings of V. van Gogh. As with the model samples, in view of the thin superficial alteration layers that are present, high lateral resolution spectroscopic methods that make use of synchrotron radiation (SR), such as microscopic X-ray absorption near edge (μ-XANES) and X-ray fluorescence spectrometry (μ-XRF) were employed. Additionally, μ-Raman and mid-FTIR analyses were carried out to completely characterize the samples. On both paint microsamples, the local presence of reduced Cr was demonstrated by means of μ-XANES point measurements. The presence of Cr(III) was revealed in specific areas, in some cases correlated to the presence of Ba(sulfate) and/or to that of aluminum silicate compounds.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 84
DOI: 10.1021/AC1025122
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods : 1 : artificially aged model samples”. Monico L, van der Snickt G, Janssens K, de Nolf W, Miliani C, Verbeeck J, Tian H, Tan H, Dik J, Radepont M, Cotte M, Analytical chemistry 83, 1214 (2011). http://doi.org/10.1021/ac102424h
Abstract: On several paintings by artists of the end of the 19th century and the beginning of the 20th Century a darkening of the original yellow areas, painted with the chrome yellow pigment (PbCrO4, PbCrO4·xPbSO4, or PbCrO4·xPbO) is observed. The most famous of these are the various Sunflowers paintings Vincent van Gogh made during his career. In the first part of this work, we attempt to elucidate the degradation process of chrome yellow by studying artificially aged model samples. In view of the very thin (1−3 μm) alteration layers that are formed, high lateral resolution spectroscopic methods such as microscopic X-ray absorption near edge (μ-XANES), X-ray fluorescence spectrometry (μ-XRF), and electron energy loss spectrometry (EELS) were employed. Some of these use synchrotron radiation (SR). Additionally, microscopic SR X-ray diffraction (SR μ-XRD), μ-Raman, and mid-FTIR spectroscopy were employed to completely characterize the samples. The formation of Cr(III) compounds at the surface of the chrome yellow paint layers is particularly observed in one aged model sample taken from a historic paint tube (ca. 1914). About two-thirds of the chromium that is present at the surface has reduced from the hexavalent to the trivalent state. The EELS and μ-XANES spectra are consistent with the presence of Cr2O3·2H2O (viridian). Moreover, as demonstrated by μ-XANES, the presence of another Cr(III) compound, such as either Cr2(SO4)3·H2O or (CH3CO2)7Cr3(OH)2 [chromium(III) acetate hydroxide], is likely.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 113
DOI: 10.1021/ac102424h
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“Recent trends in quantitative aspects of microscopic X-ray fluorescence analysis”. Janssens K, de Nolf W, van der Snickt G, Vincze L, Vekemans B, Terzano R, Brenker FE, Trends in analytical chemistry 29, 464 (2010). http://doi.org/10.1016/J.TRAC.2010.03.003
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 8.442
Times cited: 48
DOI: 10.1016/J.TRAC.2010.03.003
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“Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy”. Swaenen M, Stefaniak EA, Frost R, Worobiec A, Van Grieken R, Analytical and bioanalytical chemistry 397, 2659 (2010). http://doi.org/10.1007/S00216-009-3351-2
Abstract: Several specimens of Libyan desert glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1007/S00216-009-3351-2
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“Atomic spectroscopy: a review”. Bings NH, Bogaerts A, Broekaert JAC, Analytical chemistry 82, 4653 (2010). http://doi.org/10.1021/ac1010469
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 65
DOI: 10.1021/ac1010469
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“Theoretical characterization of an atmospheric pressure glow discharge used for analytical spectrometry”. Martens T, Mihailova D, van Dijk J, Bogaerts A, Analytical chemistry 81, 9096 (2009). http://doi.org/10.1021/ac9017742
Abstract: We have investigated the plasma processes in an atmospheric pressure glow discharge (APGD) in He used for analytical spectrometry by means of fluid and Monte Carlo (MC) simulations. Typical results include the potential and electric field distributions in the plasma, the density profiles of the various plasma species throughout the discharge, the mean electron energy, as well as the rates of the various collision processes in the plasma, and the relative importance of the different production and loss rates for the various species. The similarities and differences with low-pressure glow discharges are discussed. The main differences are a very small cathode dark space region and a large positive column as well as the dominant role of molecular ions. Some characteristic features of the APGD, such as the occurrence of the different spatial zones in the discharge, are illustrated, with links to experimental observations.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 15
DOI: 10.1021/ac9017742
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“Optimized transport setup for high repetition rate pulse-separated analysis in laser ablation-inductively coupled plasma mass spectrometry”. Lindner H, Autrique D, Garcia CC, Niemax K, Bogaerts A, Analytical chemistry 81, 4241 (2009). http://doi.org/10.1021/ac802627x
Abstract: An optimized laser ablation setup, proposed for high repetition rate inductively coupled plasma mass spectrometry (ICPMS) analyses such as 2D imaging or depth profiling, is presented. For such applications, the particle washout time needs to be as short as possible to allow high laser pulse frequencies for reduced analysis time. Therefore, it is desirable to have an ablation setup that operates as a laminar flow reactor (LFR). A top-down strategy was applied that resulted in the present design. In the first step, a previously applied ablation setup was analyzed on the basis of computational fluid dynamics (CFD) results presented by D. Autrique et al. (Spectrochim. Acta, B 2008, 63, 257−270). By means of CFD simulations, the design was modified in such a way that it operated in the LFR regime. Experimental results demonstrate that the current design can indeed be regarded as an LFR. Furthermore, the operation under LFR conditions allowed some insight into the initial radial concentration distribution if the experimental ICPMS signal and analytical expressions are taken into account. Recommendations for a modified setup for more resilient spatial distributions are given. With the present setup, a washout time of 140 ms has been achieved for a 3% signal area criterion. Therefore, 7 Hz repetition rates can be applied with the present setup. Using elementary formulas of the analytical model, an upper bound for the washout times for similar setups can be predicted. The authors believe that the presented setup geometry comes close to the achievable limit for reliable short washout times.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 18
DOI: 10.1021/ac802627x
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“Characterization of a degraded cadmium yellow (CdS) pigment in an oil painting by means of synchrotron radiation based X-ray techniques”. van der Snickt G, Dik J, Cotte M, Janssens K, Jaroszewicz J, de Nolf W, Groenewegen J, van der Loeff L, Analytical chemistry 81, 2600 (2009). http://doi.org/10.1021/AC802518Z
Abstract: On several paintings of James Ensor (1860−1949), a gradual fading of originally bright yellow areas, painted with the pigment cadmium yellow (CdS), is observed. Additionally, in some areas exposed to light, the formation of small white-colored globules on top of the original paint surface is observed. In this paper the chemical transformation leading to the color change and to the formation of the globules is elucidated. Microscopic X-ray absorption near-edge spectroscopy (ì-XANES) experiments show that sulfur, originally present in sulfidic form (S2−), is oxidized during the transformation to the sulfate form (S6+). Upon formation (at or immediately below the surface), the highly soluble cadmium sulfate is assumed to be transported to the surface in solution and reprecipitates there, forming the whitish globules. The presence of cadmium sulfate (CdSO4·2H2O) and ammonium cadmium sulfate [(NH4)2Cd(SO4)2] at the surface is confirmed by microscopic X-ray diffraction measurements, where the latter salt is suspected to result from a secondary reaction of cadmium sulfate with ammonia. Measurements performed on cross sections reveal that the oxidation front has penetrated into the yellow paint down to ca. 1−2 ìm. The morphology and elemental distribution of the paint and degradation product were examined by means of scanning electron microscopy equipped with an energy-dispersive spectrometer (SEM-EDS) and synchrotron radiation based micro-X-ray fluorescence spectrometry (SR ì-XRF). In addition, ultraviolet-induced visible fluorescence photography (UIVFP) revealed itself to be a straightforward technique for documenting the occurrence of this specific kind of degradation on a macroscale by painting conservators.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 91
DOI: 10.1021/AC802518Z
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“Single-run ion chromatographic separation of inorganic and low-molecular-mass organic anions under isocratic elution: application to environmental samples”. Krata A, Kontozova-Deutsch V, Bencs L, Deutsch F, Van Grieken R, Talanta : the international journal of pure and applied analytical chemistry 79, 16 (2009). http://doi.org/10.1016/J.TALANTA.2009.02.044
Abstract: For the isocratic ion chromatography (IC) separation of low-molecular-mass organic acids and inorganic anions three different anion-exchange columns were studied: IonPac AS14 (9 ìm particle size), Allsep A-2 (7 ìm particle size), and IC SI-50 4E (5 ìm particle size). A complete baseline separation for all analyzed anions (i.e., F−, acetate, formate, Cl−, NO2−, Br−, NO3−, HPO42− and SO42−) in one analytical cycle of shorter than 17 min was achieved on the IC SI-50 4E column, using an eluent mixture of 3.2 mM Na2CO3 and 1.0 mM NaHCO3 with a flow rate of 1.0 mL min−1. On the IonPac AS14 column, it was possible to separate acetate from inorganic anions in one run (i.e., less than 9 min), but not formate, under the following conditions: 3.5 mM Na2CO3 plus 1.0 mM NaHCO3 with a flow rate of 1.2 mL min−1. Therefore, it was necessary to adapt a second run with a 2.0 mM Na2B4O7 solution as an eluent under a flow rate of 0.8 mL min−1 for the separation of organic ions, which considerably enlarged the analysis time. For the Allsep A-2 column, using an eluent mixture of 1.2 mM Na2CO3 plus 1.5 mM NaHCO3 with a flow rate of 1.6 mL min−1, it was possible to separate almost all anions in one run within 25 min, except the fluoride-acetate critical pair. A Certified Multianion Standard Solution PRIMUS for IC was used for the validation of the analytical methods. The lowest RSDs (less than 1%) and the best LODs (0.02, 0.2, 0.16, 0.11, 0.06, 0.05, 0.04, 0.14 and 0.09 mg L−1 for F−, Ac−, For−, Cl−, NO2−, Br−, NO3−, HPO42− and SO42−, respectively) were achieved using the IC SI-50 4E column. This column was applied for the separation of concerned ions in environmental precipitation samples such as snow, hail and rainwater.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.TALANTA.2009.02.044
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“Visualization of a lost painting by Vincent van Gogh using synchrotron radiation based X-ray fluorescence elemental mapping”. Dik J, Janssens K, van der Snickt G, van der Loeff L, Rickers K, Cotte M, Analytical chemistry 80, 6436 (2008). http://doi.org/10.1021/AC800965G
Abstract: Vincent van Gogh (1853−1890), one of the founding fathers of modern painting, is best known for his vivid colors, his vibrant painting style, and his short but highly productive career. His productivity is even higher than generally realized, as many of his known paintings cover a previous composition. This is thought to be the case in one-third of his early period paintings. Van Gogh would often reuse the canvas of an abandoned painting and paint a new or modified composition on top. These hidden paintings offer a unique and intimate insight into the genesis of his works. Yet, current museum-based imaging tools are unable to properly visualize many of these hidden images. We present the first-time use of synchrotron radiation based X-ray fluorescence mapping, applied to visualize a womans head hidden under the work Patch of Grass by Van Gogh. We recorded decimeter-scale, X-ray fluorescence intensity maps, reflecting the distribution of specific elements in the paint layers. In doing so we succeeded in visualizing the hidden face with unprecedented detail. In particular, the distribution of Hg and Sb in the red and light tones, respectively, enabled an approximate color reconstruction of the flesh tones. This reconstruction proved to be the missing link for the comparison of the hidden face with Van Goghs known paintings. Our approach literally opens up new vistas in the nondestructive study of hidden paint layers, which applies to the oeuvre of Van Gogh in particular and to old master paintings in general.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 178
DOI: 10.1021/AC800965G
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“Method for the determination of Pd-catalyst residues in active pharmaceutical ingredients by means of high-energy polarized-beam energy dispersive X-ray fluorescence”. Marguí, E, van Meel K, Van Grieken R, Buendía A, Fontás C, Hidalgo M, Queralt I, Analytical chemistry 81, 1404 (2009). http://doi.org/10.1021/AC8021373
Abstract: In medicinal chemistry, Pd is perhaps the most-widely utilized precious metal, as catalyst in reactions which represent key transformations toward the synthesis of new active pharmaceutical ingredients (APIs). The disadvantage of this metal-catalyzed chemistry is that expensive and toxic metal residues are invariably left bound to the desired product. Thus, stringent regulatory guidelines exist for the amount of residual Pd that a drug candidate is allowed to contain. In this work, a rapid and simple method for the determination of Pd in API samples by high-energy polarized-beam energy dispersive X-ray fluorescence spectrometry has been developed and validated according to the specification limits of current legislation (10 mg kg−1 Pd) and the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH guidelines). Sample and calibration standards preparation includes a first step of homogenization and then, in a second step, the pressing of the powdered material into pellets without any chemical treatment. The use of several synthetic calibration standards made of cellulose to simulate the API matrix appears to be an effective means to obtain reliable calibration curves with a good spread of data points over the working range. With the use of the best measuring conditions, the limit of detection (0.11 mg kg−1 Pd) as well as the limit of quantitation (0.37 mg kg−1 Pd) achieved meet rigorous requirements. The repeatability of the XRF measurement appeared to be less than 2%, while the precision of the whole method was around 7%. Trueness was evaluated by analyzing spiked API samples at the level of the specification limit and calculating the recovery factor, which was better than 95%. To study the applicability of the developed methodology for the intended purpose, three batches of the studied API were analyzed for their Pd content, and the attained results were comparable to those obtained by the daily routine method (acid digestion plus atomic spectroscopy) used in most pharmaceutical laboratories.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1021/AC8021373
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“Atomic spectroscopy”. Bings NH, Bogaerts A, Broekaert JAC, Analytical chemistry 80, 4317 (2008). http://doi.org/10.1021/ac8006297
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 53
DOI: 10.1021/ac8006297
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“Compositional analysis of Tuscan glass samples: in search of raw materials fingerprints”. Cagno S, Janssens K, Mendera M, Analytical and bioanalytical chemistry 391, 1389 (2008). http://doi.org/10.1007/S00216-008-1945-8
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.431
Times cited: 26
DOI: 10.1007/S00216-008-1945-8
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“Investigating morphological changes in treated vs. untreated stone building materials by x-ray micro-CT”. Bugani S, Camaiti M, Morselli L, Van de Casteele E, Janssens K, Analytical and bioanalytical chemistry 391, 1343 (2008). http://doi.org/10.1007/S00216-008-1946-7
Keywords: A1 Journal article; Vision lab; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.431
Times cited: 25
DOI: 10.1007/S00216-008-1946-7
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“Advantages of combined mu-XRF and mu-XRD for phase characterization of Ti-B-C ceramics compared with conventional X-ray diffraction”. Jaroszewicz J, de Nolf W, Janssens K, Michalski A, Falkenberg G, Analytical and bioanalytical chemistry 391, 1129 (2008). http://doi.org/10.1007/S00216-008-2097-6
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.431
Times cited: 7
DOI: 10.1007/S00216-008-2097-6
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“Euroanalysis 14: the European Conference on Analytical Chemistry”. Janssens K, van Espen P, Van 't dack L, Analytical and bioanalytical chemistry 391, 1107 (2008). http://doi.org/10.1007/S00216-008-2114-9
Keywords: Editorial; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Chemometrics (Mitac 3)
Impact Factor: 3.431
DOI: 10.1007/S00216-008-2114-9
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“Particulate matter analysis at elementary schools in Curitiba, Brazil”. Avigo D, Godoi AFL, Janissek PR, Makarovska Y, Krata A, Potgieter-Vermaak S, Alfoldy B, Van Grieken R, Godoi RHM, Analytical and bioanalytical chemistry 391, 1459 (2008). http://doi.org/10.1007/S00216-008-2031-Y
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1007/S00216-008-2031-Y
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“High-energy polarized-beam energy-dispersive X-ray fluorescence analysis combined with activated thin layers for cadmium determination at trace levels in complex environmental liquid samples”. Marguí, E, Fontàs C, van Meel K, Van Grieken R, Queralt I, Hidalgo M, Analytical chemistry 80, 2357 (2008). http://doi.org/10.1021/AC7018427
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1021/AC7018427
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