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  • 1
    Language: English
    In: Analytical chemistry, 19 November 2013, Vol.85(22), pp.10643-7
    Description: Studying the environmental fate of engineered or natural colloids requires efficient methods for measuring their size and quantifying them in the environment. For example, an ideal method should maintain its correctness, accuracy, reproducibility, and robustness when applied to samples contained in complex matrixes and distinguish the target particles from the natural colloidal background signals. Since it is expected that a large portion of nanoparticles will form homo- or heteroagglomerates when released into environmental media, it is necessary to differentiate agglomerates from primary particles. At present, most sizing techniques do not fulfill these requirements. In this study, we used online coupling of two promising complementary sizing techniques: hydrodynamic chromatography (HDC) and single-particle ICPMS analysis to analyze gold nanoparticles agglomerated under controlled conditions. We used the single-particle mode of the ICPMS detector to detect single particles eluted from an HDC-column and determine a mass and an effective diameter for each particle using a double calibration approach. The average agglomerate relative density and fractal dimension were calculated using these data and used to follow the morphological evolution of agglomerates over time during the agglomeration process. The results demonstrate the ability of HDC coupled to single-particle analysis to identify and characterize nanoparticle homoagglomerates and is a very promising technique for the analysis of colloids in complex media.
    Keywords: Nanopartikel ; Einzelpartikel ; Chromatographie ; Partikelanalyse ; Eichen (Abgleichen) ; Agglomerieren ; Fraktale Dimension ; Kolloid ; Gold ; Basis (Grundlage) ; Agglomerat ; Flankendurchmesser ; Massenspektrometrie Mit Induktiv Gekoppeltem Plasma ; Engineering ; Chemistry;
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 2
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(2), p.e90559
    Description: In this study, we evaluated hydrodynamic chromatography (HDC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) for the analysis of nanoparticles in environmental samples. Using two commercially available columns (Polymer Labs-PDSA type 1 and 2), a set of well characterised...
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: Analytical chemistry, 07 August 2018, Vol.90(15), pp.8793-8799
    Description: The use of plastic materials in daily life, industry, and agriculture can cause soil pollution with plastic fragments down to the micrometer scale, i.e., microplastics. Quantitative assessment of microplastics in soil has been limited so far. Until now, microplastic analyses in soil require laborious sample cleanup and are mostly restricted to qualitative assessments. In this study, we applied thermogravimetry-mass spectrometry (TGA-MS) to develop a method for the direct quantitative analysis of poly(ethylene terephthalate) (PET) without further sample pretreatment. For this, soil samples containing 1.61 ± 0.15 wt % organic matter were spiked with 0.23-4.59 wt % PET bottle recyclate microplastics. dl-Cysteine was used as the internal standard (IS). Sample mixtures were pyrolyzed with a 5 K min ramp (40-1000 °C), while sample mass loss and MS signal intensity of typical PET pyrolysis products were recorded. We found MS signal intensities linearly responding to microplastic concentrations. The most-promising results were obtained with the IS-corrected PET pyrolysis product vinylbenzene/benzoic acid ( m/ z = 105, adj. R = 0.987). The limits of detection and quantification were 0.07 and 1.72 wt % PET, respectively. Our results suggest that TGA-MS can be an easy and viable complement to existing methods such as pyrolysis or thermogravimetry-thermal desorption assays followed by gas chromatography/mass spectrometry detection or to spectral microscopy techniques.
    Keywords: Microplastics ; Quantitative-Analysis ; Pyrolysis ; Terephthalate ; Soil-Pollution ; Soil-Analysis ; Ground-Samples ; Mass-Reduction ; Cysteine ; Benzoic-Acid ; Agricultural-Industry ; Fragment ; Organic-Medium ; Detection-Limit ; Thermogravimetric-Analysis ; Spectral-Technique ; Mikroplastik ; Quantitative Analyse ; Pyrolyse ; Terephthalat ; Bodenverschmutzung ; Bodenanalyse ; Bodenprobe ; Massenverringerung ; Cystein ; Benzoesäure ; Agrikultur ; Fragment ; Organisches Material ; Nachweisgrenze ; Thermogravimetrie ; Spektralverfahren ; Engineering ; Chemistry;
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 4
    Language: English
    In: Journal of Colloid And Interface Science, 15 April 2018, Vol.516, pp.446-455
    Description: Soil water repellency originating from organic coatings plays a crucial role for soil hydraulics and plant water uptake. Focussing on hydrophobicity in the rhizosphere induced by root-mucilage, this study aims to explore the link between macroscopic wettability and nano-microscopic surface properties. The existing knowledge of the nanostructures of organic soil compounds and its effect on wettability is limited by the lack of a method capable to assess the natural spatial heterogeneity of physical and chemical properties. In this contribution, this task is tackled by a geostatistical approach via variogram analysis of topography and adhesion force data acquired by atomic force microscopy and macroscopic sessile drop measurements on dried films of mucilage. The results are discussed following the wetting models given by Wenzel and Cassie-Baxter. Undiluted mucilage formed homogeneous films on the substrate with contact angles 〉90°. For diluted samples contact angles were smaller and incomplete mucilage surface coverage with hole-like structures frequently exhibited increased adhesion forces. Break-free distances of force curves indicated enhanced capillary forces due to adsorbed water films at atmospheric RH (35 ± 2%) that promote wettability. Variogram analysis enabled a description of complex surface structures exceeding the capability of comparative visual inspection.
    Keywords: Soil Water Repellency ; Root-Mucilage ; Contact Angle ; Atomic Force Microscopy ; Adhesion ; Nanomechanical Mapping ; Variogram ; Engineering ; Chemistry
    ISSN: 0021-9797
    E-ISSN: 1095-7103
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  • 5
    Language: English
    In: PLoS ONE, 2011, Vol.6(5), p.e20112
    Description: The production and use of nanoparticles (NP) has steadily increased within the last decade; however, knowledge about risks of NP to human health and ecosystems is still scarce. Common knowledge concerning NP effects on freshwater organisms is largely limited to standard short-term (≤48 h) toxicity tests, which lack both NP fate characterization and an understanding of the mechanisms underlying toxicity. Employing slightly longer exposure times (72 to 96 h), we found that suspensions of nanosized (∼100 nm initial mean diameter) titanium dioxide (nTiO 2 ) led to toxicity in Daphnia magna at nominal concentrations of 3.8 (72-h EC 50 ) and 0.73 mg/L (96-h EC 50 ). However, nTiO 2 disappeared quickly from the ISO-medium water phase, resulting in toxicity levels as low as 0.24 mg/L (96-h EC 50 ) based on measured concentrations. Moreover, we showed that nTiO 2 (∼100 nm) is significantly more toxic than non-nanosized TiO 2 (∼200 nm) prepared from the same stock suspension. Most importantly, we hypothesized a mechanistic chain of events for nTiO 2 toxicity in D. magna that involves the coating of the organism surface with nTiO 2 combined with a molting disruption. Neonate D. magna (≤6 h) exposed to 2 mg/L nTiO 2 exhibited a “biological surface coating” that disappeared within 36 h, during which the first molting was successfully managed by 100% of the exposed organisms. Continued exposure up to 96 h led to a renewed formation of the surface coating and significantly reduced the molting rate to 10%, resulting in 90% mortality. Because coating of aquatic organisms by manmade NP might be ubiquitous in nature, this form of physical NP toxicity might result in widespread negative impacts on environmental health.
    Keywords: Research Article ; Biology ; Chemistry ; Earth Sciences ; Materials Science ; Medicine ; Chemistry ; Public Health And Epidemiology ; Marine And Aquatic Sciences ; Ecology ; Critical Care And Emergency Medicine ; Science Policy ; Biochemistry ; Non-clinical Medicine
    E-ISSN: 1932-6203
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  • 6
    Language: English
    In: Analytical and Bioanalytical Chemistry, 2012, Vol.403(9), pp.2529-2540
    Description: Biogeochemical interfaces in soil are dynamic in the spatial and temporal domain and require advanced visualisation and quantification tools to link in vitro experiments with natural systems. This study presents the development, characterization and application of functional nanoparticles coated with monoclonal antibodies to visualise the distribution of benzo[a]pyrene in porous media using magnetic resonance imaging. The labelled particles are 450 nm in diameter and interact with benzo[a]pyrene covalently bound to silanized silica gel. They did not bind to benzo[a]pyrene adsorbed to plain silica gel. Although unspecific filtration was low, washing steps are required for visualisation. The ability to visualise benzo[a]pyrene is inversely correlated to the heterogeneity of the soil materials. There are access restrictions to narrow pore spaces which allow the visualisation of only those pathways which are also accessible to bacteria and hydrocolloids. The production of the particles is applicable to other antibodies which extends the range of potential target contaminants.
    Keywords: PAH ; Magnetic resonance imaging (MRI) ; MRI label ; NMR relaxometry ; Anti-B[a]P antibody ; Biogeochemical interface
    ISSN: 1618-2642
    E-ISSN: 1618-2650
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  • 7
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 20 August 2013, Vol.431, pp.150-160
    Description: The effect of grain water repellency on transport and deposition of hydrophilic colloids was studied by analyzing the breakthrough behavior of carboxylate-modified microspheres in water-saturated wettable and hydrophobic sand columns at different ionic strengths. Interaction free energies calculated from zeta ( )-potential and contact angle data were used to explain the specific colloid breakthrough behavior. Experimental breakthrough data could be well described with the finite-element code HYDRUS-1D using a one kinetic site model with attachment and detachment kinetics. Higher colloid deposition rates found for the hydrophobic sand could primarily be explained by its small electron-donor component of surface free energy ( = 1.6 × 10 mJ m , compared to = 64.1 mJ m for the wettable sand), leading to strongly attractive acid–base interactions at separation distances 〈 5 nm. Increasing ionic strength reduced the repulsive electrostatic interactions and generally increased colloid deposition with the effect being more pronounced in the hydrophobic sand. It can be concluded that grain water repellency tends to increase the deposition of negatively charged hydrophilic colloids, which can be ascribed to specific acid–base interactions. However, our results further revealed that the calculated interaction free energy profiles should be considered only as an approximation showing general trends because surface chemical heterogeneity as detected by atomic forces microscopy impeded the determination of the actual interaction energy conditions, resulting in an overestimation of electrostatic repulsion.
    Keywords: Acid–Base Interaction ; Carboxylate-Modified Microspheres ; Colloid Breakthrough ; Interaction Free Energy ; Surface Free Energy Components ; Wettability ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
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  • 8
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005, Vol.265(1), pp.163-170
    Description: In this study, hydration of a peat sample was investigated with differential scanning calorimetry (DSC) in terms of glass transition behavior and the formation of freezable and unfreezable water. Special attention was drawn to the development of these characteristics in the course of hydration and to plasticizing and antiplasticizing effects of water. Freezable water was formed above a water content threshold of = (23 ± 7)% and revealed structured melting peaks indicating freezable bulk-like water and freezable bound water. The freezable bound water revealed a broad, kinetically controlled melting endotherm, and the melting barrier increased with increasing hydration time. Glass transitions were found in between 43 °C and 68 °C with a change in heat capacity of Δ = (0.13 ± 0.08) J g K . Glass transition behavior does not fully match the theoretical expectations and is linked with water binding. Water reveals a short-term plasticizing function in the range of days as well as a slow antiplasticizing function in the range of weeks or even months. The findings are consistent with the hydrogen bond based cross-linking model (HBCL) suggested in a previous study. Non-equilibrium and matrix relaxation are considered the rule rather than the exception in nature and underline the ecological relevance of hydration, the relevance for sorption and transport phenomena was well as possibly for soil development.
    Keywords: Hydration ; Peat ; Plasticizer ; Antiplasticizer ; Unfreezable Water ; Glass Transition ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
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  • 9
    Language: German
    In: CHEMKON, July 2014, Vol.21(3), pp.135-137
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1002/ckon.201410228/abstract Byline: Christopher Jahnel, Gabriele E. Schaumann, Bjorn Risch Keywords: Modellexperiment; Tenside; Umwelt ***** No abstract is available for this article. ***** Author Affiliation: Universitat Koblenz-Landau, Campus Landau, Institut fur Umweltwissenschaften, AG Umwelt- und Bodenchemie, Fortstr. 7, 76829 Landau Universitat Koblenz-Landau, Campus Landau, Institut fur naturwissenschaftliche Bildung, AG Chemiedidaktik, Fortstra[sz]e 7, 76829 Landau
    Keywords: Modellexperiment ; Tenside ; Umwelt
    ISSN: 0944-5846
    E-ISSN: 1521-3730
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  • 10
    Language: English
    In: Thermochimica Acta, 10 November 2016, Vol.643, pp.73-82
    Description: Water molecule bridges (WaMB), representing linkages between functional groups in organic matter, are hypothesized to stabilize the supramolecular structure of the soil organic matter (SOM). As the underlying mechanisms are largely unknown, partly due to the high heterogeneity, complexity and amorphicity in SOM, a more general understanding on the processes potentially underlying WaMB formation and disruption can be accomplished by exploring a simpler model system. We examined in a first step and for the first time the mechanism of water liberation in a well-defined model system, α-oxalic acid dihydrate, using XRPD, FT-IR, DSC and solid state H NMR. In a second step, we evaluated the potential of the transfer of this knowledge to the processes occurring in SOM. According to XRPD, dehydration occurs at about 70 °C and it is accompanied by a change in the crystal system from monoclinic to orthorhombic. Temperature-dependent FT-IR spectra, apart from confirming the findings of XRPD, reveal the changes in hydrogen bonding pattern upon transformation of the dihydrate to the anhydrous compound. DSC thermograms obtained in two subsequent heating and cooling runs suggest a reversibility and heating-rate independence in breaking and re-forming of hydrogen bonds between oxalic acid moieties and water molecules in temperature range * ∼ 60–76 °C. The latter is also confirmed by solid state H NMR spectra. Similarly to α-oxalic acid dihydrate, disruption of WaMB in SOM occurs in that temperature range, but does not reappear immediately in the second heating run and it is heating-rate dependent, which points to a relevance of structural relaxation processes in SOM. Simultaneous monitoring of spectral signatures changes and detection of the water release temperature suggests that temperature-dependent FT-IR spectroscopy might be a helpful method to monitor WaMB disruption and formation in SOM.
    Keywords: Α-Oxalic Acid Dihydrate ; Α-Oxalic Acid Anhydride ; Hydrogen Bonding ; X-Ray Powder Diffraction ; Ft-IR Spectroscopy ; Differential Scanning Calorimetry ; Chemistry
    ISSN: 0040-6031
    E-ISSN: 1872-762X
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