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“Rapid classification and quantification of cocaine in seized powders with ATR-FTIR and chemometrics”. Eliaerts J, Dardenne P, Meert N, Van Durme F, Samyn N, Janssens K, De Wael K, Drug testing and analysis 9, 1480 (2017). http://doi.org/10.1002/DTA.2149
Abstract: Traditionally, fast screening for the presence of cocaine in unknown powders is performed by means of colour tests. The major drawbacks of these tests are subjective colour evaluation depending on the operator (50 shades of blue) and a lack of selectivity. An alternative fast screening technique is Fourier Transform InfraRed (FTIR) spectrometry. This technique provides spectra that are difficult to interpret without specialized expertise and showing a lack of sensitivity for the detection of cocaine in mixtures. To overcome these limitations, a portable FTIR spectrometer using Attenuated Total Reflectance (ATR) sampling was combined with a multivariate technique, called Support Vector Machines (SVM). Representative street drug powders (n = 482), seized during the period January 2013 to July 2015, and reference powders (n = 33) were used to build and validate a classification model (n = 515) and a quantification model (n = 378). Both models were compared with the conventional chromatographic techniques. The SVM classification model showed a high sensitivity, specificity and efficiency (99%). The SVM quantification model determined cocaine content with a root mean squared error of prediction (RMSEP) of 6% calculated over a wide working range from 4 to 99 w%. In conclusion, the developed models resulted in a clear output (cocaine detected or cocaine not detected) and a reliable estimation of the cocaine content in a wide variety of mixtures. The ATR-FTIR technique combined with SVM is a straightforward, user-friendly and fast approach for routine classification and quantification of cocaine in seized powders.
Keywords: A1 Journal article; Pharmacology. Therapy; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.469
Times cited: 9
DOI: 10.1002/DTA.2149
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“Cooperative electrocatalytic and chemoselective alcohol oxidation by Shvo's catalyst”. Lybaert J, Trashin S, Maes BUW, De Wael K, Abbaspour Tehrani K, Advanced synthesis and catalysis 359, 919 (2017). http://doi.org/10.1002/ADSC.201600783
Abstract: A new electrocatalytic conversion of alcohols to ketones and aldehydes was developed based on an electrochemical study of Shvos complex. The oxidation of secondary alcohols was efficiently performed under mild conditions using a catalytic amount of Shvos catalyst, in combination with a sub-stoichiometric amount of 2,6-dimethoxy-1,4- benzoquinone in N,N-dimethylformamide at 80 8C. The hydroquinone thus formed is continuously reoxidized with the aid of an electrochemical device. Excellent yields for different ketones, aromatic as well as aliphatic and a,b-unsaturated ketones, are obtained. In addition, chemoselectivity towards oxidation of the secondary alcohol is achieved when converting vicinal diols such as 1,2-octanediol and 1,2-decanediol.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Organic synthesis (ORSY)
Impact Factor: 5.646
Times cited: 4
DOI: 10.1002/ADSC.201600783
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“Non-invasive and non-destructive examination of artistic pigments, paints, and paintings by means of X-Ray methods”. Janssens K, van der Snickt G, Vanmeert F, Legrand S, Nuyts G, Alfeld M, Monico L, Anaf W, de Nolf W, Vermeulen M, Verbeeck J, De Wael K, Topics in Current Chemistry 374, 81 (2016). http://doi.org/10.1007/S41061-016-0079-2
Abstract: Recent studies are concisely reviewed, in which X-ray beams of (sub)micrometre to millimetre dimensions have been used for non-destructive analysis and characterization of pigments, minute paint samples, and/or entire paintings from the seventeenth to the early twentieth century painters. The overview presented encompasses the use of laboratory and synchrotron radiation-based instrumentation and deals with the use of several variants of X-ray fluorescence (XRF) as a method of elemental analysis and imaging, as well as with the combined use of X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Microscopic XRF is a variant of the method that is well suited to visualize the elemental distribution of key elements, mostly metals, present in paint multi-layers, on the length scale from 1 to 100 μm inside micro-samples taken from paintings. In the context of the characterization of artists pigments subjected to natural degradation, the use of methods limited to elemental analysis or imaging usually is not sufficient to elucidate the chemical transformations that have taken place. However, at synchrotron facilities, combinations of μ-XRF with related methods such as μ-XAS and μ-XRD have proven themselves to be very suitable for such studies. Their use is often combined with microscopic Fourier transform infra-red spectroscopy and/or Raman microscopy since these methods deliver complementary information of high molecular specificity at more or less the same length scale as the X-ray microprobe techniques. Since microscopic investigation of a relatively limited number of minute paint samples, taken from a given work of art, may not yield representative information about the entire artefact, several methods for macroscopic, non-invasive imaging have recently been developed. Those based on XRF scanning and full-field hyperspectral imaging appear very promising; some recent published results are discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.033
Times cited: 50
DOI: 10.1007/S41061-016-0079-2
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“Unique opto-electronic structure and photo reduction properties of sulfur doped lead chromates explaining their instability in paintings”. Rahemi V, Sarmadian N, Anaf W, Janssens K, Lamoen D, Partoens B, De Wael K, Analytical chemistry 89, 3326 (2017). http://doi.org/10.1021/ACS.ANALCHEM.6B03803
Abstract: Chrome yellow refers to a group of synthetic inorganic pigments that became popular as an artists material from the second quarter of the 19th century. The color of the pigment, in which the chromate ion acts as a chromophore, is related to its chemical composition (PbCr1-xSxO4, with 0≤x≤0.8) and crystalline structure (monoclinic/orthorhombic). Their shades range from the yellow-orange to the paler yellow tones with increasing sulfate amount. These pigments show remarkable signs of degradation after limited time periods. Pure PbCrO4 (crocoite in its natural form) has a deep yellow color and is relatively stable, while the co-precipitate with lead sulfate (PbCr1-xSxO4) has a paler shade and seems to degrade faster. This degradation is assumed to be related to the reduction of Cr(VI) to Cr(III). We show that on increasing the sulfur(S)-content in chrome yellow, the band gap increases. Typically, when increasing the band gap, one might assume that a decrease in photo activity is the result. However, the photo activity relative to the Cr content, and thus Cr reduction, of sulfur-rich PbCr1-xSxO4 is found to be much higher compared to the sulfur-poor or non-doped lead chromates. This discrepancy can be explained by the evolution of the crystal and electronic structure as function of the sulfur content: first-principles density functional theory calculations show that both the absorption coefficient and reflection coefficients of the lead chromates change as a result of the sulfate doping in such a way that the generation of electron-hole pairs under illumination relative to the total Cr content increases. These changes in the material properties explain why paler shade yellow colors of this pigment are more prone to discoloration. The electronic structure calculations also demonstrate that lead chromate and its co-precipitates are p-type semiconductors, which explains the observed reduction reaction. As understanding this phenomenon is valuable in the field of cultural heritage, this study is the first joint action of photo-electrochemical measurements and first-principles calculations to approve the higher tendency of sulfur-rich lead chromates to darken.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 7
DOI: 10.1021/ACS.ANALCHEM.6B03803
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“The effect of the buffer solution on the adsorption and stability of horse heart myoglobin on commercial mesoporous titanium dioxide : a matter of the right choice”. Loreto S, Cuypers B, Brokken J, Van Doorslaer S, De Wael K, Meynen V, Physical chemistry, chemical physics 19, 13503 (2017). http://doi.org/10.1039/C6CP08585G
Abstract: Despite the numerous studies on the adsorption of different proteins onto mesoporous titanium dioxide and indications on the important role of buffer solutions in bioactivity, a systematic study on the impact of the buffer on the protein incorporation into porous substrates is still lacking. We here studied the interaction between a commercial mesoporous TiO2 and three of the most used buffers for protein incorporation, i.e. HEPES, Tris and phosphate buffer. In addition, this paper analyzes the adsorption of horse heart myoglobin (hhMb) onto commercial mesoporous TiO2 as a model system to test the influence of buffers on the protein incorporation behavior in mesoporous TiO2. N2 sorption analysis, FT-IR and TGA/DTG measurements were used to evaluate the interaction between the buffers and the TiO2 surface, and the effect of such an interaction on hhMb adsorption. Cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) were used to detect changes in the microenvironment surrounding the heme. The three buffers show a completely different interaction with the TiO2 surface, which drastically affects the adsorption of myoglobin as well as its structure and electrochemical activity. Therefore, special attention is required while choosing the buffer medium to avoid misguided evaluation of protein adsorption on mesoporous TiO2.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.123
Times cited: 2
DOI: 10.1039/C6CP08585G
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“X-Ray Fluorescence as an analytical tool for studying the copper matrices in the collection of the Museum Plantin-Moretus”. Storme P, Fransen E, De Wael K, Caen J, De gulden passer 95, 7 (2017)
Keywords: A1 Journal article; Engineering sciences. Technology; History; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
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“Mediated electrolysis of vicinal diols by neocuproine palladium catalysts”. Lybaert J, Tehrani KA, De Wael K, Electrochimica acta 247, 685 (2017). http://doi.org/10.1016/J.ELECTACTA.2017.07.044
Abstract: Synthetic electrochemistry agrees well with the principles of sustainable chemistry, therefore it is considered as a more environmentally friendly approach than some current synthetic methods Here, we present a new strategy for the chemoselective oxidation of vicinal diols, viz. the integration of neocuproine palladium catalysts and electrosynthesis. Benzoquinones are used as an effective mediator as the reduced species (hydroquinones) can be easily reoxidized at relative low potentials at an electrode surface. NeocuproinePd(OAc)2 efficiently works as a catalyst in an electrolysis reaction for vicinal diols at room temperature. This is a remarkable observation given the fact that aerobic oxidation reactions of alcohols typically need a more complex catalyst, i.e. [neocuproinePdOAc]2[OTf]2. In this article we describe the optimization of the electrolysis conditions for the neocuproinePd(OAc)2 catalyst to selectively oxidize diols. The suggested approach leads to conversion of alcohols with high yields and provides an interesting alternative to perform oxidation reactions under mild conditions by the aid of electrochemistry.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Organic synthesis (ORSY)
Impact Factor: 4.798
DOI: 10.1016/J.ELECTACTA.2017.07.044
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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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“Photodegradation mechanisms and kinetics of Eosin-Y in oxic and anoxic conditions”. Alvarez-Martin A, Trashin S, Cuykx M, Covaci A, De Wael K, Janssens K, Dyes and pigments 145, 376 (2017). http://doi.org/10.1016/J.DYEPIG.2017.06.031
Abstract: Lakes based on Eosin-Y are extensively used by 19th century artists. Unfortunately, the identification of these pigments in paintings is a difficult task because Eosin-Y degrades very fast under the influence of light. The characterization of the (photo)degradation products of Eosin-Y can be very useful for the identification of these pigments in historic works of art and related cultural heritage artifacts. Furthermore, knowledge on how different factors influence the discoloration process (e.g. different types of irradiation sources and presence/absence of oxygen) is a valuable tool for preventive conservation. To this aim we performed a study on the photodegradation of Eosin-Y in solution under different illumination and in both oxic and anoxic conditions. The photodegradation of Eosin-Y was monitored by UV-VIS spectrophotometry, LC-QTOFMS and electrochemistry techniques. Results indicated higher degradation rates, by a factor of 20 or higher, under illumination with wavelengths near to the main absorbance band of the red pigment. Two different degradation pathways are observed under the conditions studied. LC-QTOFMS and electrochemistry suggested that in the presence of oxygen the degradation mechanism is an oxidative process where the breakdown of the structure causes the total discoloration. Meanwhile under anoxic conditions, a debromination process takes place while the chromophore, and consequently the color of the molecule in solution, remains essentially intact.
Keywords: A1 Journal article; Pharmacology. Therapy; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Toxicological Centre
Impact Factor: 3.473
Times cited: 18
DOI: 10.1016/J.DYEPIG.2017.06.031
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“Singlet oxygen-based electrosensing by molecular photosensitizers”. Trashin S, Rahemi V, Ramji K, Neven L, Gorun SM, De Wael K, Nature communications 8, 16108 (2017). http://doi.org/10.1038/NCOMMS16108
Abstract: Enzyme-based electrochemical biosensors are an inspiration for the development of (bio)analytical techniques. However, the instability and reproducibility of the reactivity of enzymes, combined with the need for chemical reagents for sensing remain challenges for the construction of useful devices. Here we present a sensing strategy inspired by the advantages of enzymes and photoelectrochemical sensing, namely the integration of aerobic photocatalysis and electrochemical analysis. The photosensitizer, a bioinspired perfluorinated Zn phthalocyanine, generates singlet-oxygen from air under visible light illumination and oxidizes analytes, yielding electrochemically-detectable products while resisting the oxidizing species it produces. Compared with enzymatic detection methods, the proposed strategy uses air instead of internally added reactive reagents, features intrinsic baseline correction via on/off light switching and shows C-F bonds-type enhanced stability. It also affords selectivity imparted by the catalytic process and nano-level detection, such as 20 nM amoxicillin in μl sample volumes.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 12.124
Times cited: 26
DOI: 10.1038/NCOMMS16108
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“Antarctic fish versus human cytoglobins : the same but yet so different”. Cuypers B, Vermeylen S, Hammerschmid D, Trashin S, Rahemi V, Konijnenberg A, De Schutter A, Cheng C-HC, Giordano D, Verde C, De Wael K, Sobott F, Dewilde S, Van Doorslaer S, Journal of inorganic biochemistry 173, 66 (2017). http://doi.org/10.1016/J.JINORGBIO.2017.04.025
Abstract: The cytoglobins of the Antarctic fish Chaenocephalus aceratus and Dissostichus mawsoni have many features in common with human cytoglobin. These cytoglobins are heme proteins in which the ferric and ferrous forms have a characteristic hexacoordination of the heme iron, i.e. axial ligation of two endogenous histidine residues, as confirmed by electron paramagnetic resonance, resonance Raman and optical absorption spectroscopy. The combined spectroscopic analysis revealed only small variations in the heme-pocket structure, in line with the small variations observed for the redox potential. Nevertheless, some striking differences were also discovered. Resonance Raman spectroscopy showed that the stabilization of an exogenous heme ligand, such as CO, occurs differently in human cytoglobin in comparison with Antarctic fish cytoglobins. Furthermore, while it has been extensively reported that human cytoglobin is essentially monomeric and can form an intramolecular disulfide bridge that can influence the ligand binding kinetics, 3D modeling of the Antarctic fish cytoglobins indicates that the cysteine residues are too far apart to form such an intramolecular bridge. Moreover, gel filtration and mass spectrometry reveal the occurrence of non-covalent multimers (up to pentamers) in the Antarctic fish cytoglobins that are formed at low concentrations. Stabilization of these oligomers by disulfide-bridge formation is possible, but not essential. If intermolecular disulfide bridges are formed, they influence the heme-pocket structure, as is shown by EPR measurements.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.348
Times cited: 7
DOI: 10.1016/J.JINORGBIO.2017.04.025
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“Indoor environmental quality index for conservation environments : the importance of including particulate matter”. Marchetti A, Pilehvar S, 't Hart L, Leyva Pernia D, Voet O, Anaf W, Nuyts G, Otten E, Demeyer S, Schalm O, De Wael K, Building and environment 126, 132 (2017). http://doi.org/10.1016/J.BUILDENV.2017.09.022
Abstract: It is commonly known that the conservation state of works of arts exhibited inside museums is strongly influenced by the indoor environmental quality (IEQ). Heritage institutions traditionally record and evaluate their IEQ by monitoring temperature, relative humidity, and -more rarely-light. However, smart use of technology enables monitoring other parameters that give a more complete insight in environmental air aggressiveness. One of this parameters is particulate matter (PM) and especially its concentration, size distribution and chemical composition. In this work, we present a selection of data sets which were obtained in a measuring campaign performed in the War Heritage Institute in Brussels, Belgium. A continuous monitoring of PM concentration with a light scattering based particle counter was performed. In addition the daily mass concentration and size distribution of airborne PM was monitored by means of Harvard impactors. The chemical composition of sampled PM was inferred from the results of XRF and IC analysis. The insights from these datasets are combined with the results of traditional environmental monitoring (temperature, relative humidity and light intensity), and assessed against the recommended guidelines for conservation environments. By using an integrated approach based on the calculation of an IEQ-index, we present a straightforward methodology to evaluate and visualize the IEQ including also continuous PM monitoring. It is clear from the results of this study how including PM in IEQ analysis allows to identify potential risks for museum collections that remain invisible when only traditional parameters are considered.
Keywords: A1 Journal article; Engineering sciences. Technology; Antwerp Systems and software Modelling (AnSyMo); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp Cultural Heritage Sciences (ARCHES)
Impact Factor: 4.053
Times cited: 10
DOI: 10.1016/J.BUILDENV.2017.09.022
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“Electrodeposition of gold nanoparticles on boron doped diamond electrodes for the enhanced reduction of small organic molecules”. Bottari F, De Wael K, Journal of electroanalytical chemistry : an international journal devoted to all aspects of electrode kynetics, interfacial structure, properties of electrolytes, colloid and biological electrochemistry. 801, 521 (2017). http://doi.org/10.1016/J.JELECHEM.2017.07.053
Abstract: The performance of gold nanoparticles electrodeposited on boron doped diamond (BDD) electrodes was investigated in respect to the reduction of chloramphenicol (CAP), an antibiotic of the phenicols family. The chosen deposition protocol, three nucleation-growing pulses, shows a remarkable surface coverage, with an even distribution of average-sized gold particles (~ 50 nm), and it was proven capable of generating a three-fold increase in the CAP reduction current. A calibration plot for CAP detection was obtained in the micromolar range (535 μM) with good correlation coefficient (0.9959) and an improved sensitivity of 0.053 μA μM− 1 mm− 2 compared to the electrochemistry of CAP at a bare BDD electrode.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.012
Times cited: 4
DOI: 10.1016/J.JELECHEM.2017.07.053
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“Recent advances in electrochemical biosensors based on fullerene-C60 nano-structured platforms”. Pilehvar S, De Wael K page 173 (2017).
Keywords: H1 Book chapter; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“The application of an electrochemical microflow reactor for the electrosynthetic aldol reaction of acetone to diacetone alcohol”. Pauwels D, Geboes B, Hereijgers J, Choukroun D, De Wael K, Breugelmans T, Chemical engineering research and design 128, 205 (2017). http://doi.org/10.1016/J.CHERD.2017.10.014
Abstract: The design and application of an electrochemical micro-flow reactor for the aldol reaction of acetone to diacetone alcohol (DAA) is reported. The modular reactor could be readily disassembled and reassembled to change the electrodes, incorporate a membrane and remove possible obstructions. The productivity and efficiency was quantified. Using a platinum deposit as electrocatalyst or an inert glassy carbon electrode as working electrode, the maximum obtainable equilibrium concentration of ±15 m% was reached after a single pass up to a flow rate of 8 ml min−1, yielding 0.57 g min−1 DAA (3.46 mmol cm−3 min−1) at an efficiency of 0.33 g C−1 on platinum and 0.50 g min−1 (3.04 mmol cm−3 min−1) at 1.20 g C−1 on glassy carbon. Note that no optimisation studies have been made in the present paper.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 2.538
Times cited: 2
DOI: 10.1016/J.CHERD.2017.10.014
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“Practical tool for sampling and fast analysis of large cocaine seizures”. Eliaerts J, Meert N, Van Durme F, Samyn N, De Wael K, Dardenne P, Drug testing and analysis 10, 1039 (2018). http://doi.org/10.1002/DTA.2364
Abstract: Large quantities of illicit drugs are frequently seized by law enforcement. In such cases, a representative number of samples needs to be quickly examined prior to destruction. No procedure has yet been set up which rapidly provides information regarding the homogeneity of the samples, the presence of controlled substances and the degree of purity. This study establishes a protocol for fast analysis of cocaine and its most common cutting agent, levamisole, in large seizures. The protocol is based on a hypergeometric sampling approach combined with FTIR spectrometry and Support Vector Machines (SVM) algorithms as analysis methods. To demonstrate the practical use of this approach, five large cocaine seizures (consisting between 45 and 85 units) were analysed simultaneously with GC-MS, GC-FID and a portable FTIR spectrometer using Attenuated Total Reflectance (ATR) sampling combined with SVM models. According to the hypergeometric sampling plan of the Drugs Working Group ENFSI guidelines, the required number of subsamples ranged between 19 and 23. Considering the identification analyses, the SVM models detected cocaine and levamisole in all subsamples of cases 1 to 5 (100% correct classification), which was confirmed by GC-MS analysis. Considering the quantification analyses, the SVM models were able to estimate the cocaine and levamisole content in each subsample, compared to GC-FID data. The developed strategy is easy, cost effective and provides immediate information about both the presence and concentration of cocaine and levamisole. By using this new strategy, the number of confirmation analyses with laborious and expensive chromatographic techniques could be significantly reduced.
Keywords: A1 Journal article; Pharmacology. Therapy; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.469
Times cited: 1
DOI: 10.1002/DTA.2364
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“A simplified protocol for usage of new immuno-SERS probes for detection of casein, collagens and ovalbumin in cross-sections of artworks”. Hrdlickova Kuckova S, Hamidi-Asl E, Sofer Z, Marvan P, De Wael K, Sanyova J, Janssens K, Analytical methods 10, 1054 (2018). http://doi.org/10.1039/C7AY01864A
Abstract: Although it is now relatively straightforward to identify protein binders in works of art, their proper localization within the corresponding layer still represents a significant analytical challenge. Until now, the identification of proteins has mainly been performed by peptide mass fingerprinting using mass spectrometric methods and their localization in polished paint cross-sections have been realized by optical microscopy via the use of fluorescent stain Sypro Ruby (SR). In this work we propose a simplified protocol for immuno-surface enhanced Raman scattering (immuno-SERS) using gold nanoparticles attached to biphenyl-4,4-dithiol (BPDT) as the SERS-nanotag. These nanoparticles are easily obtainable in the lab and have been used to label multilayered mock up samples prepared as cross-sections to estimate the detection limits of the suggested method. The layers contain egg, casein, and different animal glues binders (prepared in various ratios with linseed oil or a carbohydrate component) mixed with the pigments azurite, vermilion and chalk. The sensitivity of staining agent SR is compared to that of the immuno-SERS protocol for the first time.
Keywords: A1 Journal article; Pharmacology. Therapy; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.9
Times cited: 3
DOI: 10.1039/C7AY01864A
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“Levamisole : a common adulterant in cocaine street samples hindering electrochemical detection of cocaine”. De Jong M, Florea A, de Vries A-M, van Nuijs ALN, Covaci A, Van Durme F, Martins JC, Samyn N, De Wael K, Analytical chemistry 90, 5290 (2018). http://doi.org/10.1021/ACS.ANALCHEM.8B00204
Abstract: The present work investigates the electrochemical determination of cocaine in the presence of levamisole, one of the most common adulterants found in cocaine street samples. Levamisole misleads cocaine color tests, giving a blue color (positive test) even in the absence of cocaine. Moreover, the electrochemical detection of cocaine is also affected by the presence of levamisole, with a suppression of the oxidation signal of cocaine. When levamisole is present in the sample in ratios higher than 1:1, the cocaine signal is no longer detected, thus leading to false negative results. Mass spectrometry and nuclear magnetic resonance were used to investigate if the signal suppression is due to the formation of a complex between cocaine and levamisole in bulk solution. Strategies to eliminate this suppressing effect are further suggested in this manuscript. In a first approach, the increase of the pH of the sample solution from pH 7 to pH 12 allowed the voltammetric determination of cocaine in the presence of levamisole in a concentration range from 10 to 5000 μM at nonmodified graphite disposable electrodes with a detection limit of 5 μM. In a second approach, the graphite electrode was cathodically pretreated, resulting in the presence of oxidation peaks of both cocaine and levamisole, with a detection limit for cocaine of 3 μM over the linear range of concentrations from 10 to 2500 μM. Both these strategies have been successfully applied for the simultaneous detection of cocaine and levamisole in three street samples on unmodified graphite disposable electrodes.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Toxicological Centre
Impact Factor: 6.32
Times cited: 8
DOI: 10.1021/ACS.ANALCHEM.8B00204
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“Assessing the stability of arsenic sulfide pigments and influence of the binding media on their degradation by means of spectroscopic and electrochemical techniques”. Vermeulen M, Janssens K, Sanyova J, Rahemi V, McGlinchey C, De Wael K, Microchemical journal 138, 82 (2018). http://doi.org/10.1016/J.MICROC.2018.01.004
Abstract: In this paper, we used the semiconducting and lightfastness properties of synthetic and mineral arsenic sulfide pigments to study their stability by means of electrochemical and microfadometric techniques. A combination of these techniques shows that in the early stage of the degradation process, amorphous arsenic sulfides are more stable than both crystalline forms, while upon longer exposure time, amorphous pigments will fade more than both mineral pigments, making it less suitable. While the stability study was carried out on unbound pigments, the influence of the organic binder on the relative degradation of the arsenic sulfide pigments was investigated through a multi-analytical approach on pigment/binder mock-up paint samples. For this purpose, the formation of arsenic trioxide was assessed by micro Fourier transform infrared (μ-FTIR) spectroscopy while the influence of the binder on the formation of sulfates was studied by means of synchrotron radiation X-ray near edge structure (μ-XANES). Both techniques elucidate a higher stability of all pigments in gum arabic while the use of egg yolk as binder leads to the most degradation, most likely due to its sulfur-rich composition. In the context of the degradation of arsenic sulfide pigments, other binders such as animal glue, egg white or linseed oil show an intermediate impact.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.034
Times cited: 4
DOI: 10.1016/J.MICROC.2018.01.004
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“Identifying intermediates in the reductive intramolecular cyclisation of allyl 2-bromobenzyl ether by an improved electron paramagnetic resonance spectroelectrochemical electrode design combined with density functional theory calculations”. Pauwels D, Ching HYV, Samanipour M, Neukermans S, Hereijgers J, Van Doorslaer S, De Wael K, Breugelmans T, Electrochimica acta 271, 10 (2018). http://doi.org/10.1016/J.ELECTACTA.2018.03.093
Abstract: The electrochemical activation of C-X bonds requires very negative electrode potentials. Lowering the overpotentials and increasing the catalytic activity requires intensive electrocatalytic research. A profound understanding of the reaction mechanism and the influence of the electrocatalyst allows optimal tuning of the electrocatalyst. This can be achieved by combining electrochemical techniques with electron paramagnetic resonance (EPR) spectroscopy. Although this was introduced in the mid-twentieth century, the application of this combined approach in electrocatalytic research is underexploited. Several reasons can be listed, such as the limited availability of EPR instrumentation and electrochemical devices for such in situ experiments. In this work, a simple and inexpensive construction adapted for in situ EPR electrocatalytic research is proposed. The proof of concept is provided by studying a model reaction, namely the reductive cyclisation of allyl 2-bromobenzyl ether which has interesting industrial applications.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 4.798
Times cited: 2
DOI: 10.1016/J.ELECTACTA.2018.03.093
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“Polymer platforms for selective detection of cocaine in street samples adulterated with levamisole”. Florea A, Cowen T, Piletsky S, De Wael K, Talanta : the international journal of pure and applied analytical chemistry 186, 362 (2018). http://doi.org/10.1016/J.TALANTA.2018.04.061
Abstract: Accurate drug detection is of utmost importance for fighting against drug abuse. With a high number of cutting agents and adulterants being added to cut or mask drugs in street powders the number of false results is increasing. We demonstrate for the first time the usefulness of employing polymers readily synthesized by electrodeposition to selectively detect cocaine in the presence of the commonly used adulterant levamisole. The polymers were selected by computational modelling to exhibit high binding affinity towards cocaine and deposited directly on the surface of graphene-modified electrodes via electropolymerization. The resulting platforms allowed a distinct electrochemical signal for cocaine, which is otherwise suppressed by levamisole. Square wave voltammetry was used to quantify cocaine alone and in the presence of levamisole. The usefulness of the platforms was demonstrated in the screening of real street samples.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.162
Times cited: 9
DOI: 10.1016/J.TALANTA.2018.04.061
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“Tailoring the functional properties of polyurethane foam with dispersions of carbon nanofiber for power generator applications”. Sathiyamoorthy S, Girijakumari G, Kannan P, Venugopal K, Thiruvottriyur Shanmugam S, Veluswamy P, De Wael K, Ikeda H, Applied surface science 449, 507 (2018). http://doi.org/10.1016/J.APSUSC.2018.01.088
Abstract: To produce effective thermoelectric nanocomposites, carbon nanofibers (CNF) incorporated polyurethane (PU) foams with nanocomposites are prepared via in-situ polymerization method to create a synergy that would produce a high thermopower. The formation mechanism of foams, the reaction kinetics, and the physical properties such as density and water absorption studied before and after CNF incorporation. The microscopy images showed a uniform dispersion of CNF in the PU matrix of the prepared foams. Spectroscopic studies such as X-ray photoelectron and laser Raman spectroscopy suggested the existence of a tight intermolecular binding interaction between the carbon nanofibers and the PU matrix in the prepared composite foams. It found that the thermopower is directly dependent on the concentration of carbon nanofiber since, with rising concentration of 1%3%, the coefficient values increased from 1.2 μV/K to 11.9 μV/K respectively, a value higher than that of earlier report. This unique nanocomposite offers a new opportunity to recycle waste heat in portable/wearable electronics and other applications, which will broaden the development of low weight and mechanical flexibility.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.387
Times cited: 4
DOI: 10.1016/J.APSUSC.2018.01.088
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“Optical readout of controlled monomer-dimer self-assembly”. Tarakanov PA, Tarakanova EN, Dorovatovskii PV, Zubavichus YV, Khrustalev VN, Trashin SA, De Wael K, Neganova ME, Mischenko DV, Sessler JL, Stuzhin PA, Pushkarev VE, Tomilova LG, Journal of the Chemical Society : Dalton transactions 47, 14169 (2018). http://doi.org/10.1039/C8DT00384J
Abstract: 5,7-Substituted 1,4-diazepinoporphyrazine magnesium(II) complexes were synthesized via Mg(II)-alkoxide templated macrocyclization. A single crystal growth synchrotron diffraction analysis permitted what is to our knowledge the first structural characterization of a 1,4-diazepinoporphyrazine. It exists as a dimer in the solid state. In silico calculations supported by solution phase spectral studies involving a series of representative derivatives, provided insights into the factors governing dimerization of 1,4-diazepinoporphyrazines. The present 1,4-diazepinoporphyrazines serve as useful probes for understanding the determinants that guide dimermonomer equilibria and the self-assembly of phthalocyanine derivatives.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 4
DOI: 10.1039/C8DT00384J
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“Tackling poor specificity of cocaine color tests by electrochemical strategies”. De Jong M, Florea A, Eliaerts J, Van Durme F, Samyn N, De Wael K, Analytical chemistry 90, 6811 (2018). http://doi.org/10.1021/ACS.ANALCHEM.8B00876
Abstract: This paper presents electrochemical strategies for the fast screening of cocaine and most common cutting agents found in seized drug samples. First, a study on the performance of Scott color tests on cocaine and a wide range of cutting agents is described. The cutting agents causing false positive or false negative results when in mixture with cocaine are identified. To overcome the lack of specificity of color tests, we further propose a fast screening strategy by means of square wave voltammetry on disposable graphite screen printed electrodes, which reveals the unique fingerprint of cocaine and cutting agents. By employing a forward and backward scan and by a dual pH strategy, we enrich the electrochemical fingerprint and enable the simultaneous detection of cocaine and cutting agents. The effectiveness of the developed strategies was tested for the detection of cocaine in seized cocaine samples and compared with the color tests. Moreover, we prove the usefulness of square wave voltammetry for predicting possible interfering agents in color tests, based on the reduction peak of cobalt thiocyanate. The developed electrochemical strategies allow for a quick screening of seized cocaine samples resulting in a selective identification of drugs and cutting agents.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 7
DOI: 10.1021/ACS.ANALCHEM.8B00876
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“Technoques and applications of Surface-Enhanced Raman Scattering Spectroscopy (SERSS) focused on cultural heritage”. Kuckova S, Hamidi-Asl E, Matulkova I, Hynek R, De Wael K, Sanyova J, Janssens K, Chemické, listy 112, 312 (2018)
Abstract: The review is devoted to a modern method of vibrational spectroscopy – surface enhanced Raman spectroscopy Its principle and some of its special variants (imunnoSERS and TERS (Tip-Enhanced Raman Spectroscopy)) are described m a simpinified manner Wide application possibilities are demonstrated on selected examples from its application m culturinl heritage.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 0.387
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“Electrochemical strategies for the detection of forensic drugs”. Florea A, De Jong M, De Wael K, Current opinion in electrochemistry 11, 34 (2018). http://doi.org/10.1016/J.COELEC.2018.06.014
Abstract: Illicit drugs consumption and trafficking is spread worldwide and remains an increasing challenge for local authorities. Forensic drugs and their metabolites are released into wastewaters due to human excretion after illegal consumption of drugs and occasionally due to disposal of clandestine laboratory wastes into sewage systems, being recently classified as the latest group of emerging pollutants. Hence, it is essential to have efficient and accurate methods to detect these type of compounds in seized street samples, biological fluids and wastewaters in order to reduce and prevent trafficking and consumption and negative effects on aquatic systems. Electrochemical strategies offer a fast, portable, low-cost and accurate alternative to chromatographic and spectrometric methods, for the analysis of forensic drugs and metabolites in different matrices. Recent electrochemical strategies applied to the detection of illicit drugs in wastewaters, biological fluids and street samples are presented in this review, together with the impact of drug consumption on the environment.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 7
DOI: 10.1016/J.COELEC.2018.06.014
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“Leaf-deposited semi-volatile organic compounds (SVOCs) : an exploratory study using GCxGC-TOFMS on leaf washing solutions”. Castanheiro A, Joos P, Wuyts K, De Wael K, Samson R, Chemosphere 214, 103 (2019). http://doi.org/10.1016/J.CHEMOSPHERE.2018.09.067
Abstract: Airborne particulate matter (PM) includes semi-volatile organic compounds (SVOCs), which can be deposited on vegetation matrices such as plant leaves. In alternative to air-point measurements or artificial passive substrates, leaf monitoring offers a cost-effective, time-integrating means of assessing local air quality. In this study, leaf washing solutions from ivy (Hedera hibernica) leaves exposed during one-month at different land use classes were explored via comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-TOFMS). The composition of leaf-deposited SVOCs, corrected for those of unexposed leaves, was compared against routinely monitored pollutants concentrations (PM10, PM2.5, O3, NO2, SO2) measured at co-located air monitoring stations. The first study on leaf-deposited SVOCs retrieved from washing solutions, herein reported, delivered a total of 911 detected compounds. While no significant land use (rural, urban, industrial, traffic, mixed) effects were observed, increasing exposure time (from one to 28 days) resulted in a higher number and diversity of SVOCs, suggesting cumulative time-integration to be more relevant than local source variations between sites. After one day, leaf-deposited SVOCs were mainly due to alcohols, N-containing compounds, carboxylic acids, esters and lactones, while ketones, diketones and hydrocarbons compounds gained relevance after one week, and phenol compounds after one month. As leaf-deposited SVOCs became overall more oxidized throughout exposure time, SVOCs transformation or degradation at the leaf surface is suggested to be an important phenomenon. This study confirmed the applicability of GCxGC-TOFMS to analyze SVOCs from leaf washing solutions, further research should include validation of the methodology and comparison with atmospheric organic pollutants.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.208
DOI: 10.1016/J.CHEMOSPHERE.2018.09.067
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“A new opportunity for biomagnetic monitoring of particulate pollution in an urban environment using tree branches”. Wuyts K, Hofman J, van Wittenberghe S, Nuyts G, De Wael K, Samson R, Atmospheric environment : an international journal 190, 177 (2018). http://doi.org/10.1016/J.ATMOSENV.2018.07.014
Abstract: Environmental magnetism, and the magnetic leaf signal in particular, is amply investigated and applied as proxy for atmospheric particulate matter pollution. In this study, we investigated the magnetic signal of annual segments of tree branches, and the composition of particles deposited hereon. Branches are, contrary to leaves of deciduous trees, available during leaf-off seasons and exposed to air pollution year-round. We examined the intra- and inter-tree variation in saturation isothermal remanent magnetization (SIRM) of branch internodes of London plane (Platanus x aeerifolia Willd.) trees in an urban environment. The branch SIRM, normalized by surface area, ranged from 18 to 650 x 10(-6) angstrom; the median amounted to 106 x 10(-6) angstrom. Most of the branch magnetic signal was attributed to the epidermis or bark, and the presence of metal-containing particles on the branch surfaces was confirmed by SEM-EDX. The location of the trees and the height, the depth in the crown and the age of the branches significantly influenced the branch SIRM. The median branch SIRM was up to 135% higher near a busy ring road than in quiet environments (city park and quiet street canyon), and was linked to the presence of Fe-rich particles with co-occurrence of trace metals such as Cr, Cu, Zn and Mn on the branch surface. Within the tree crowns, the branch SIRM generally decreased with increasing height, and was 22% higher in the interior than at the periphery of the crowns. Within the branches, the SIRM increased with each year of exposure, but did not relate to year-to-year variation in particle concentrations due to branch surface changes (epidermis shedding). Our results provide indications that branches can be a valuable alternative for biomagnetic monitoring of particulate pollution, but intra-tree variability in branch SIRM can be substantial due to the branch's location in the tree and branch age.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.629
Times cited: 3
DOI: 10.1016/J.ATMOSENV.2018.07.014
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“Biomonitoring of atmospheric particulate pollution via chemical composition and magnetic properties of roadside tree leaves”. Kardel F, Wuyts K, De Wael K, Samson R, Environmental Science and Pollution Research 25, 25994 (2018). http://doi.org/10.1007/S11356-018-2592-Z
Abstract: Particulate matter (PM) is a main atmospheric pollution which threats human health and well-being. In this research, we chemically and magnetically analysed roadside tree leaves, collected from three tree species in two main roads (from two different cities) and a reference area, for 28 elements and the saturation isothermal remanent magnetisation. Comparison of unwashed and washed leaves revealed that deposited particles on the leaf surface contain various elements including Al, Ca, Fe, Mg, Mn, Na, Si, Ti, Ba, Co, Cr, Cu, Ni, Rb, V, Zn and Zr. Moreover, there was no significant difference between washed/unwashed leaves in Cl, K, P, S, As, Cd, Cs, Pb, Sn and Sr concentrations, which indicates tree leaves may not be a suitable biomonitor for these elements. Our results showed that site and tree species are important factors which affect atmospheric elements deposition. Among the three considered tree species, Chamaecyparis lawsoniana showed the highest potential for atmospheric particle accumulation. The PCA results revealed that Al, Fe, Ti, Co, Cr, Cu, Ni, Rb, Si, V, Zn and Zr indicated emissions from road traffic activities and soil dust; Ca, Mg and Na from sea salts and Mn and Sb from industrial activity. The biplot results showed that the site effect was much stronger than the species effect for all elements and saturation isothermal remanent magnetisation (SIRM) values. Moreover, elements from traffic, industrial activity and soil dust are significantly correlated with leaf SIRM indicating that leaf SIRM can be a suitable bioindicator of exposure to traffic-derived particles and soil dust, and not from sea salts. It is concluded that chemical composition and SIRM of urban tree leaves can serve as a good indicator of atmospheric PM pollution in Iran and anywhere else where the studied trees grow.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 2.741
Times cited: 6
DOI: 10.1007/S11356-018-2592-Z
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“Bio(inspired) strategies for the electro-sensing of β-lactam antibiotics”. Bottari F, Blust R, De Wael K, Current opinion in electrochemistry 10, 143 (2018). http://doi.org/10.1016/J.COELEC.2018.05.016
Abstract: The dire previsions of the WHO on the so-called “post-antibiotic era” and the continuous and global rise of anti-microbial resistance, spurs our research community to find better ways to fight these threats. In light of this severe threat to human health many attempts have been made to develop efficient methods to detect antibiotic residues in different streams. The use of electrochemistry seems an inviting approach for on-site and fast monitoring. In this critical review, recent developments in the field of (bio) electro-sensing of 19-lactam antibiotics will be presented, with a focus on aptamers and molecularly imprinted polymers, the two main promises of a new generation of biosensors, yet to be fulfilled.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Times cited: 15
DOI: 10.1016/J.COELEC.2018.05.016
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