Publications by authors named "Kristof Tirez"

A critical comparison of the main parameters playing a role in measurement of electrophoretic mobility of plastic nanoparticles (NPs) by CE and laser Doppler velocimetry (LDV) techniques in NP suspensions is herein presented, accompanied by a discussion about potential impact on different mobility values observed. Capillary material and dynamic or permanent coating of the inner capillary wall, capillary dimensions, EOF variability, BGE temperature, Joule heating, and presence of species potentially interacting with analyzed NPs are underlined as possible causes of the different performance of the above two techniques. It is of importance to get an insight into the reasons behind experimental conditions and operating features to opt for one technique or the other based on research interests.

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Capillary electrophoresis (CE) is presented as a technique for the separation of polystyrene nanoparticles (NPs, particle diameters ranging from 30 to 300 nm) through a bare fused silica capillary and ultraviolet detection. The proposed strategy was also assessed for other types of nanoplastics, finding that stronger alkaline conditions, with an ammonium hydroxide buffer (7.5%, pH = 11.

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Accurate characterization of Pt-Pd alloy nanoparticle clusters (NCs) is crucial for understanding their synthesis using Gas-Diffusion Electrocrystallization (GDEx). In this study, we propose a comprehensive approach that integrates conventional sizing techniques-scanning electron microscopy (SEM) and dynamic light scattering (DLS)-with innovative single-particle inductively coupled plasma-sector field mass spectrometry (spICP-SFMS) to investigate Pt-Pd alloy NC formation. SEM and DLS provide insights into morphology and hydrodynamic sizes, while spICP-SFMS elucidates the particle size and distribution of Pt-Pd alloy NCs, offering rapid and orthogonal characterization.

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The Sea Scheldt estuary has been suggested to be a significant pathway for transfer of plastic debris to the North Sea. We have studied 12,801 plastic items that were collected in the Sea Scheldt estuary (Belgium) during 3 sampling campaigns (in spring, summer, and autumn) using a technique called anchor netting. The investigation results indicated that the abundance of plastic debris in the Scheldt River was on average 1.

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A new comprehensive analytical approach based on single-particle inductively coupled plasma-sector field mass spectrometry (spICP-SFMS) and electrical asymmetric-flow field-flow-fractionation combined with multi-angle light scattering detection (EAF4-MALS) has been examined for the characterization of galactosamine-terminated poly(N-hydroxyethyl acrylamide)-coated gold nanorods (GNRs) in two different degrees of polymerization (DP) by tuning the feed ratio (short: DP 35; long: DP 60). spICP-SFMS provided information on the particle number concentration, size and size distribution of the GNRs, and was found to be useful as an orthogonal method for fast characterization of GNRs. Glycoconjugated GNRs were separated and characterized via EAF4-MALS in terms of their size and charge and compared to the bare GNRs.

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Development of analytical methods for the characterization (particle size determination, identification, and quantification) of the micro- and nanoscale plastic debris in the environment is a quickly emerging field and has gained considerable attention, not only within the scientific community, but also on the part of policy makers and the general public. In this Trends paper, the importance of developing and further improving analytical methodologies for the detection and characterization of sub-20-μm-range microplastics and especially nanoplastics is highlighted. A short overview of analytical methodologies showing considerable promise for the detection and characterization of such micro- and nanoscale plastic debris is provided, with emphasis on recent developments in mass spectrometry (MS)-based analytical methods.

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Article Synopsis
  • Chronic exposure to food-grade titanium dioxide (E171) raises health concerns due to its potential inflammatory effects and ability to promote gut lesions.
  • Researchers studied how TiO is absorbed in the intestines of mice, finding peak absorption in certain areas at 4 hours post-administration before it dropped, while some absorption continued to occur in the Peyer's patches at 8 hours.
  • The study identified that significantly more TiO absorption happens via pathways related to goblet cells and that blocking certain tight junctions greatly reduces absorption, indicating complex mechanisms of uptake in the gut.
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HO was demonstrated to narrow the size distribution and decrease the size of CuO and hydrous FeOOH (2-line ferrihydrite) nanoparticles under conditions of high supersaturation. We introduce oxidation-assisted alkaline precipitation (Ox-AP) and compare it to traditional alkaline precipitation (AP). While for AP, a metal salt solution (, CuCl) is mixed with an alkali (, NaOH), for Ox-AP, the more reduced form of that metal salt solution (, CuCl) is simultaneously mixed with that alkali and an oxidant (, HO).

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A new prototype air-liquid interface (ALI) exposure system, a flatbed aerosol exposure chamber termed NAVETTA, was developed to investigate deposition of engineered nanoparticles (NPs) on cultured human lung A549 cells directly from the gas phase. This device mimics human lung cell exposure to NPs due to a low horizontal gas flow combined with cells exposed at the ALI. Electrostatic field assistance is applied to improve NP deposition efficiency.

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Despite many investigations have focused on the pristine toxicity of gold nanoparticles (GNPs), little is known about the outcome of co-exposure and interaction of GNPs with heavy metals which can possibly detoxify or potentiate them. Here, the combined exposure of nickel (II) sulfate (NiSO) and GNPs on the maturation response of dendritic cells (DCs) was explored. Exposure to GNPs or NiSO separately induced cell activation.

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Undoubtedly, the most important advance in the environmental regulatory monitoring of elements of the last decade is the widespread introduction of ICP-mass spectrometry (ICP-MS) due to standards developed by the European Committee for Standardization. The versatility of ICP-MS units as a tool for the determination of major, minor and trace elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Se, Sn, Ti, V and Zn) in surface water, groundwater, river sediment, topsoil, subsoil, fine particulates and atmospheric deposition is illustrated in this paper. Ranges of background concentrations for major, minor and trace elements obtained from a regional case study (Flanders, Belgium) are summarized for all of these environmental compartments and discussed in the context of a harmonized implementation of European regulatory monitoring requirements.

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Rationale: The phosphorylation of proteins is one of the most important post-translational modifications in nature. Knowledge of the quantity or degree of protein phosphorylation in biological samples is extremely important. A combination of liquid chromatography (LC) and inductively coupled plasma mass spectrometry (ICP-MS) allows the absolute and relative quantification of the phosphorus signal.

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Reversible phosphorylation is one of the most important post-translational modifications in mammalian cells. Because this molecular switch is an important mechanism that diversifies and regulates proteins in cellular processes, knowledge about the extent and quantity of phosphorylation is very important to understand the complex cellular interplay. Although phosphoproteomics strategies are applied worldwide, they mainly include only molecular mass spectrometry (like MALDI or ESI)-based experiments.

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In spite of increasing efforts to reduce nitrogen inputs into ground water from intensive agriculture, nitrate (NO(3)) remains one of the major pollutants of drinking-water resources worldwide, with NO(3) levels approaching the defined limit of 50 mg l(-1) in an increasing number of water bodies. Determining the source(s) of contamination in water is an important first step for improving its quality by emission control. The Life ISONITRATE project aimed at showing the benefit of a multi-isotope approach (δ(15)N and δ(18)O of NO(3), and δ(11)B), in addition to conventional hydrogeological analysis, to track the origin of NO(3) contamination in water.

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A European standard for the determination of Cr(vi) in solid material has been elaborated in the framework of an international co-operation and finally validated in the course of an interlaboratory comparison. The procedure is based on the alkaline digestion prescribed by EPA method 3060A followed by ion chromatography and determines an operationally defined content of Cr(vi), including water-soluble and insoluble chromates. A preliminary robustness study was carried out in order to compare different extraction methodologies and to study the equivalency of different analytical methods for the determination of Cr(vi) in alkaline extracts of soil and waste materials.

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To determine the heavy metal content in soil samples at contaminated locations, a static and time consuming procedure is used in most cases. Soil samples are collected and analyzed in the laboratory at high quality and high analytical costs. The demand by government and consultants for a more dynamic approach and by customers requiring performances in which analyses are performed in the field with immediate feedback of the analytical results, is growing.

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The mercury mass fraction has been determined by atomic fluorescence spectrometry (AFS) in the framework of the project "Certification of a reference material (trace elements in fly ash) in replacement of BCR CRM 176". Calculation of the uncertainty budget, as described in this manuscript, emphasizes a practical and realistic approach to estimation of uncertainty components on the basis of statistical assumptions. GUM Workbench software was used, and resulted in a mercury mass fraction of 1.

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