Chemie und Prozesstechnik
Filtern
Dokumenttyp
- Zeitschriftenartikel (1171)
- Vortrag (1069)
- Posterpräsentation (442)
- Beitrag zu einem Tagungsband (174)
- Forschungsdatensatz (55)
- Sonstiges (43)
- Buchkapitel (24)
- Forschungsbericht (23)
- Dissertation (15)
- Beitrag zu einem Sammelband (13)
- Handbuch (5)
- Video (5)
- Zeitschriftenheft (Herausgeberschaft für das komplette Heft) (3)
- Sammelband (Herausgeberschaft für den kompletten Band) (2)
- Tagungsband (Herausgeberschaft für den kompletten Band) (1)
- Newsletter (1)
Sprache
- Englisch (3046) (entfernen)
Schlagworte
- Nanoparticles (114)
- Fluorescence (112)
- Concrete (89)
- LIBS (81)
- Mechanochemistry (72)
- Quantum yield (71)
- Ultrasound (71)
- SAXS (69)
- Non-destructive testing (68)
- XPS (61)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (1085)
- 6 Materialchemie (973)
- 8 Zerstörungsfreie Prüfung (774)
- 6.1 Oberflächen- und Dünnschichtanalyse (348)
- 6.3 Strukturanalytik (322)
- 1.1 Anorganische Spurenanalytik (277)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (232)
- 8.0 Abteilungsleitung und andere (224)
- 1.2 Biophotonik (210)
- 4 Material und Umwelt (186)
Paper des Monats
- ja (26)
Silver nanoparticles (AgNPs), have a high scientific and commercial impact due to their important antibacterial properties. However, there are serious concerns about their toxicological adverse effects as a consequence of their broad range of applications. Particularly, the impact of AgNPs on cells is not very well understood yet and there is a current demand to develop analytical methodologies providing information about the interaction and distribution of AgNPs at a single cell level. In this research, mass cytometry was used to introduce a new quantitative approach to study the uptake of AgNPs by individual THP-1 macrophages as a cell model system. Here, we show that this methodology provides not only multi-variate phenotypic information of individual cells but enables the quantitative analysis of AgNPs associated to cells in a single measurement by performing an external calibration using AgNPs suspension. Using differentiated THP-1 cells, we monitored and quantified the uptake of 50 nm AgNPs in a time and dose-dependent manner by mass cytometry. 7 to 120 AgNPs per cell (2 to 89 fg Ag/cell) were determined after exposure of differentiated THP-1 cells to low AgNPs concentrations of 0.1 and 1.0 mg L-1, at time points of 4 and 24 h. The results were validated by mass cytometric analysis of digested cells working as a conventional inductively coupled plasma mass spectrometry, ICP-MS. This study demonstrates the power of single cell analysis by mass cytometry even for low doses experiments as a new analytical tool for hitherto unaddressed questions in nanotoxicology.
Silver nanoparticles (AgNPs), have a high scientific and commercial impact due to their important antibacterial properties. However, there are serious concerns about their toxicological adverse effects as a consequence of their broad range of applications. Particularly, the impact of AgNPs on cells is not very well understood yet and there is a current demand to develop analytical methodologies providing information about the interaction and distribution of AgNPs at a single cell level. In this research, mass cytometry was used to introduce a new quantitative approach to study the uptake of AgNPs by individual THP-1 macrophages as a cell model system. Here, we show that this methodology provides not only multi-variate phenotypic information of individual cells but enables the quantitative analysis of AgNPs associated to cells in a single measurement by performing an external calibration using AgNPs suspension. Using differentiated THP-1 cells, we monitored and quantified the uptake of 50 nm AgNPs in a time and dose-dependent manner by mass cytometry. 7 to 120 AgNPs per cell (2 to 89 fg Ag/cell) were determined after exposure of differentiated THP-1 cells to low AgNPs concentrations of 0.1 and 1.0 mg L-1, at time points of 4 and 24 h. The results were validated by mass cytometric analysis of digested cells working as a conventional inductively coupled plasma mass spectrometry, ICP-MS. This study demonstrates the power of single cell analysis by mass cytometry even for low doses experiments as a new analytical tool for hitherto unaddressed questions in nanotoxicology.
Unprecedented Ionization Processes in Mass SpectrometryProvide Missing Link between ESI and MALDI
(2018)
In the field of mass spectrometry,producing intact, highly-charged protein ions from surfaces is a conundrum with significant potential payoff in application areas ranging from bio-medical to clinical research. Here, we report on the ability to form intact, highly-charged protein ions on high vacuum time-of-flight mass spectrometers in the linear and reflectron modes achievable using experimental conditions that allow effective matrix removal from both the sample surfaces and from the charged clusters formed by the laser Ablation event. The charge states are the highest reported on high vacuum mass spectrometers, yet they remain at only around athird of the highest charge obtained using laser ablation with a suitable matrix at atmospheric pressure. Other than physical instrument modifications, the key to forming abundant and stable highly-charged ions appears to be the volatility of the matrix used. Cumulative results suggest mechanistic links between the ionization process reported here and traditional ionization methods of electrospray ionization and matrix-assisted laser desorp-tion/ionization.
A magnetically stabilized DC arc device, designed for operation with OES spectrometers was used to determine the elements Ag, Al, B, Ba, Be, Ca, Co, Cr, Cu, Fe, Ga, In, K, Li, Mg, Mn, Mo, Na, Nb, Ni, Si, Sn, Sr, Ti, V, Zr at trace levels of some μg kg−1 up to some 10 mg kg−1 in graphite powders. The coil for the generation of the homogeneous magnetic field was placed outside the closed arc chamber. The time programs of variable current strengths of the magnetic coil (up to 6 A) and of the arc (up to 17 A) which was burning in air were computer controlled. Halogenating gases (mainly CCl2F2, alternatively SF6 and NF3) were used as chemical modifiers to allow an effective release of the carbide forming trace elements. The mass flow controlled modifier gas was led through a special carrier electrode near the arc plasma. The emission radiation was guided by an optical fiber alternatively into two different ICP spectrometers in which the ICP torches were removed. The synergistic interaction of the magnetic field with the halogenating modifier gases resulted in a significant improvement in the analytical performance of the optimized analytical method. All our results for 22 trace elements were in good agreement with the means of an inter-laboratory comparison by BAM for certification of a pure graphite powder material; this holds also for our results for two other graphite materials. The optimized method showed an analytical performance suitable for comprehensive trace analysis of pure graphite. The instrumentation could be integrated into modern DC arc emission spectrometers to improve their analytical capabilities substantially.
The detection of moisture in building materials has a high priority in civil engineering to locate and prevent possible moisture damages, e.g. mold, corrosion, delamination etc. Furthermore, it is of great significancy to achieve a better understanding of moisture transport and pore space in different materials. To prevent the degeneration of structures and materials, non-destructive testing methods are more and more deployed. As a non-destructive method in this work, nuclear magnetic resonance (NMR) is applied using a strayfield open magnet device that enables one-dimensional measurements in a defined volumen. By using NMR, the water content of the sample can be determined and also the pore size distribution can be deduced from the relaxation time distribution when having a comparison method like mercury intrusion porosimetry.
In this study different synthetic homogenous materials with defined and almost unimodal pore size distributions are investigated as well as building materials like screed. For analyzing the pore space, the samples were measured at different saturation levels and the building materials at different hydration states as well.
Proline has been widely used for various cocrystallization applications, including pharmaceutical cocrystals. Combining enantiopure and racemic flurbiprofen and proline, we discovered 18 new crystal structures. Liquid-assisted grinding proved highly efficient to explore all the variety of crystal forms. A unique combination of stateof-the-art characterization techniques, comprising variable temperature in situ X-ray diffraction and in situ ball-milling, along with other physicochemical methods and density functional theory calculations, was indispensable for identifying all the phases. Analyzing the results of in situ ball-milling, we established a stepwise mechanism for the formation of several 1:1 cocrystals via an intermediate 2:1 phase. The nature of the solvent in liquidassisted grinding was found to significantly affect the reaction rate and, in some cases, the reaction pathway.
Austenitic stainless steel welds as well as dissimilar metal welds with nickel alloy filler material, used in safety relevant parts of nuclear power plants, still challenge the ultrasonic inspection. The weld material forms large oriented grains which lead on the one hand to high sound scattering and on the other hand – to inhomogeneity and to the acoustic anisotropy of the weld structure. The ultrasonic wave fronts propagate not linearly, as in ferritic weld joints, but along the curves, which depend on the specific grain structure of the weld. Due the influence of these phenomena, it is difficult to analyze the inspection results and to classify the ultrasonic indications, which could be both from the weld geometry and from the material defects. A correct flaw sizing is not possible.
In an ongoing research project, different techniques to improve the reliability of ultrasonic testing at these kinds of welds are investigated. In a first step (in the previous research project) two ultrasonic inspection techniques were developed and validated on plane test specimens with artificial and realistic flaws. In the ongoing project, these techniques are applied to circumferential pipe welds with longitudinal and transverse flaws.
The technique developed at the Federal Institute for Materials Research and Testing (BAM) in Germany uses a combination of ray tracing and synthetic aperture focusing technique (SAFT). To investigate the unknown grain structure, the velocity distribution of weld-transmitting ultrasound waves is measured and used to model the weld by ray tracing.
The second technique, developed at the Fraunhofer Institute for Nondestructive Testing (IZFP) in Germany, uses Sampling Phased Array (Full Matrix Capture) combined with the reverse phase matching (RPM) and the gradient elastic constant descent algorithm (GECDM). This inspection method is able to estimate the elastic constants of the columnar grains in the weld and offers an improvement of the reliability of ultrasonic testing through the correction of the sound field distortion. The unknown inhomogeneity and anisotropy are investigated using a reference indication and the special optimization algorithm.
Both reconstruction techniques give quantitative inspection results and allow the defect sizing. They have been compared to conventional ultrasonic testing with techniques, which are state of the art for components in nuclear power plants. The improvement will be quantified by the comparison of the probability of detection (POD) of each technique.
The aldoximes C11H9NO (I) and C15H11NO (II), synthesized in ca 90%yield, by
treatment of 1-naphthaldehyde or phenanthrene-9-carbaldehyde, respectively,
with hydroxylamine hydrochloride and sodium carbonate, have been characterized
by IR, 1H, 13C and DEPT-135 NMR spectroscopies, and also by singlecrystal
X-ray diffraction analysis. The molecules of (I) and (II) are
conformationally similar, with the aldoxime substituent groups lying outside
the planes of the naphthalene or phenanthrene rings, forming dihedral angles
with them of 23.9 (4) and 27.9 (6)°, respectively. The crystal structures of both
(I) and (II) are similar with a single intermolecular O—H...N hydrogenbonding
interaction, giving rise to the formation of one-dimensional polymeric
chains extending along the 21 (b) screw axes in each.
An artificial digestion of silver nitrate is reported. It is shown that AgSCN nanoparticles emerge from ionic silver in saliva and remain present during the entire digestion process. The particles were characterized by infrared spectroscopy and small- and wide-angle X-ray scattering (SAXS/WAXS) regarding their composition and size distribution.
We found cascade IR generation in Al laser induced plasma. This generation includes doublet transitions 3s25s 2S1∕2→ 3s24p 2P1∕2,3∕2 → 3s24s 2S1∕2; corresponding to strong lines at 2110 and 2117 nm, and much weaker lines at 1312–1315 nm. The 3s25s2S 1∕2 starting IR generation level is directly pumped from the 3s23p 2P3∕2 ground level. The starting level for UV generation at 396.2 nm (transitions 3s24s 2S1∕2 → 4p 2P3∕2) is populated due to the fast collisional processes in the plasma plume. These differences led to different time and special dependences on the lasing in the IR and UV spectral range within the aluminum laser induced plasma.
In this article the question of the certification of calibration samples for the characterisation of advanced thin film materials is addressed within the framework of reliable process control or quality management purposes. Reference measurement techniques can be used in order to address the gap in appropriate certified reference materials (CRMs) for thin film analyses. They allow for qualifying out-of-production samples originating from an operating production line as calibration samples. As a template for this procedure, CIGS [Cu(In,Ga)Se2] layers, that are absorber layers for high efficiency thin-film solar cells, have been used for establishing and validating reference-free X-ray fluorescence (XRF) analysis and Auger-electron spectroscopy (AES) as reference measurement techniques. The focus was on determining the average mole fractions in the CIGS layers obtaining results traceable to the SI unit system. Reference-free XRF is physically traceable and is based upon radiometrically calibrated instrumentation and knowledge of atomic fundamental data. Sputter-assisted AES can be established as a chemically traceable method after careful calibration using a certified reference material (CRM) based on a total number counting method.
For the first time, an international comparison was conducted on the determination of the purity of a high purity element. Participants were free to choose any analytical approach appropriate for their institute’s applications and services. The material tested was a high purity zinc, which had earlier been assessed for homogeneity and previously used in CCQM-K72 for the determination of six defined metallic impurities. Either a direct metal assay of the Zn mass fraction was undertaken by EDTA titrimetry, or an indirect approach was used wherein all impurities, or at least the major ones, were determined and their sum subtracted from ideal purity of 100 %, or 1 kg/kg. Impurity assessment techniques included glow discharge mass spectrometry, inductively coupled plasma mass spectrometry and carrier gas hot extraction/combustion analysis. Up to 91 elemental impurities covering metals, non-metals and semi-metals/metalloids were quantified. Due to the lack of internal experience or experimental capabilities, some participants contracted external laboratories for specific analytical tasks, mainly for the analysis of non-metals. The reported purity, expressed as zinc mass fraction in the high purity zinc material, showed excellent agreement for all participants, with a relative standard deviation of 0.011 %. The calculated reference value, w(Zn) = 0.999 873 kg/kg, was assigned an asymmetric combined uncertainty of + 0.000025 kg/kg and – 0.000028 kg/kg. Comparability amongst participating metrology institutes is thus demonstrated for the purity determination of high purity metals which have no particular difficulties with their decomposition / dissolution process when solution-based analytical methods are used, or which do not have specific difficulties when direct analysis approaches are used. Nevertheless, further development is required in terms of uncertainty assessment, quantification of non-metals and the determination of purity of less pure elements and/or for those elements suffering difficulties with the decomposition process.
The paper addresses “WHITE LIGHT INTERFERENCE MICROSCOPY, ELLIPSOMETRY, AND INSTRUMENTED INDENTATION TESTING AS REFERENCE PROCEDURES“ and is subdivided in the following sections: 1. Measurement vs. testing vs. reference procedures, 2. White light interference microscopy (WLIM) for determination of step height h, 3. Spectroscopic ellipsometry (SE) for determination of layer thickness d and 4. Instrumented indentation testing (IIT) for determination of indentation hardness HIT. The following points are discussed in more detail: methodology of measurement and testing, uncertainty budgets for direct (WLIM), model-based (SE) and formula-based (IIT) reference procedures by means of specific examples. It is shown that standardization efforts are connected to reference procedures.
The overall interest in nanotoxicity, triggered by the increasing use of nanomaterials in the material and life sciences, and the synthesis of an ever increasing number of new functional nanoparticles calls for standardized test procedures1,2 and for efficient approaches to screen the potential genotoxicity of these materials. Aiming at the development of fast and easy to use, automated microscopic methods for the determination of the genotoxicity of different types of nanoparticles, we assess the potential of the fluorometric γH2AX assay for this purpose. This assay, which can be run on an automated microscopic detection system, relies on the detection of DNA double strand breaks as a sign for genotoxicity3. Here, we provide first results obtained with broadly used nanomaterials like CdSe/CdS and InP/ZnS quantum dots as well as iron oxide, gold, and polymer particles of different surface chemistry with previously tested colloidal stability and different cell lines like Hep-2 and 8E11 cells, which reveal a dependence of the genotoxicity on the chemical composition as well as the surface chemistry of these nanomaterials. These studies will be also used to establish nanomaterials as positive and negative genotoxicity controls or standards for assay performance validation for users of this fluorometric genotoxicity assay. In the future, after proper validation, this microscopic platform technology will be expanded to other typical toxicity assays.
A frequently studied environmental contaminant is the active substance diclofenac, which is removed insufficiently in sewage treatment plants. Since its inclusion in the watch list of the EU Water Framework Directive, the concentrations in surface waters will be determined throughout Europe. For this, still, more precise analytical methods are needed. As a reference, HPLC-MS is frequently employed. One of the major metabolites is 4’-hydroxydiclofenac (4’-OH-DCF). Also, diclofenac lactam is important for assessing degradation and transformation. Aceclofenac (ACF), the glycolic acid ester of diclofenac is used as a drug, too, and could potentially be cleaved to yield diclofenac again. In various sewage treatment plant influent samples, diclofenac, 4’-OH-DCF, DCF lactam and ACF could be determined with detection limits of 3 µg/L, 0.2 µg/L, 0.17 µg/L and 10 ng/L, respectively.
From simple molar mass disperse homopolymers over copolymers to functionalized, 3-dimensional structures containing various distributions, the complexity of polymeric materials has become more and more sophisticated in recent years. With applications in medicine, pharmacy, smart materials or for the semiconductor industry the requirements for the characterization have risen with the complexity of the used polymers. For each additional distribution, an additional dimension in analysis is needed. Small, often isobaric heterogeneities in topology or microstructure can usually not be simply separated chromatographically or distinguished by any common detector. Instead of a complicated, time consuming and/or expensive 2d-chromatography or ion mobility spectrometry (IMS) method, that also has its limitations, here a simple approach using size exclusion chromatography (SEC) coupled with electrospray ionization mass spectrometry (ESI) is proposed. We used SEC for the separation because unlike other separation modes the separation in this mode solely should occur due to the hydrodynamic volume with no interference of other interactions. This simplifies the interpretation and the above mentioned heterogeneities should show a slight difference in hydrodynamic volume. ESI mass spectrometry can offer more than an access to mass dependent information like MMD, end group masses or CCD in polymer analysis. The online coupling to SEC allows the analysis of reconstructed ion chromatograms (RIC) of each degree of polymerization. While a complete separation often cannot be achieved, the derived retention times and peak widths lead to information on the existence and dispersity of heterogeneities in microstructure or topology, that are otherwise inaccessible or accessible only by time consuming or expensive methods. Because these heterogeneities might vary with the molar mass, analysis of the whole MMD-Peak (here the total ion current (TIC)) would not lead to the desired information. The broadening of the chromatographic peaks in this case does not origin from the already well known band broadening factors in chromatography from diffusion. This band broadening is attributed to the nature and composition of the analyte itself. Surprisingly there is very little investigation into the peak width or peak shape due to analyte structure itself found in literature. It is also shown, that with proper calibration even quantitative information could be obtained. This method is suitable to detect small differences in e. g. branching, topology, monomer sequence or tacticity and could potentially be used in production control of oligomeric products or other routinely done analyses to quickly indicate deviations from set parameters. Based on a variety of examples we demonstrate the possibilities and limitations of this approach.
Single-cell analysis by ICP-MS/MS as a fast tool for cellular bioavailability studies of arsenite
(2018)
Single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS) has become a powerful and fast tool to evaluate the elemental composition at a single-cell level. In this study, the cellular bioavailability of arsenite (incubation of 25 and 50 μM for 0-48 h) has been successfully assessed by SC-ICP-MS/MS for the first time directly after re-suspending the cells in water. This procedure avoids the normally arising cell membrane permeabilization caused by cell fixation methods (e.g. methanol fixation). The reliability and feasibility of this SC-ICP-MS/MS approach with a limit of detection of 0.35 fg per cell was validated by conventional bulk ICP-MS/MS analysis after cell digestion and parallel measurement of sulfur and phosphorus.
Development and market introduction of new nanomaterials trigger the need for an adequate risk assessment of such products alongside suitable risk communication measures. Current application of classical and new nanomaterials is analyzed in context of regulatory requirements and standardization for chemicals, food and consumer products. The challenges of nanomaterial characterization as the main bottleneck of risk assessment and regulation are presented. In some areas, e.g., quantification of nanomaterials within complex matrices, the establishment and adaptation of analytical techniques such as laser ablation inductively coupled plasma mass spectrometry and others are potentially suited to meet the requirements. As an example, we here provide an approach for the reliable characterization of human exposure to nanomaterials resulting from food packaging. Furthermore, results of nanomaterial toxicity and ecotoxicity testing are discussed, with concluding key criteria such as solubility and fiber rigidity as important parameters to be considered in material development and regulation. Although an analysis of the public opinion has revealed a distinguished rating depending on the particular field of application, a rather positive perception of nanotechnology could be ascertained for the German public in general. An improvement of material characterization in both toxicological testing as well as end-product control was concluded as being the main obstacle to ensure not only safe use of materials, but also wide acceptance of this and any novel technology in the general public.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining importance for bioimaging cytometry to answer analytical, biological and biomedical questions. High sensitivity and spatial resolution make it an excellent tool for imaging of metal and heteroelement distribution in single cells. Comparable to CyTOF imaging mass cytometry, metal coded antibodies can be used for multiparametric analysis as well as quantification.
In this project, nanocrystals are investigated as new highly sensitive metal tags for identification and quantification of biomarkers, like Alzheimer’s or breast cancer, in clinical cell assays and tissue samples. Of high significance is the simultaneous analysis of several biomarkers at once, which is possible by special coding of lanthanide tags on the biomarker associated antibody. Nanocrystals show potential for sensitive measurement in MS due to high stability and signal amplification compared to tags with fewer metal atoms. For proof of principle, synthesis and characterization of lanthanide doped nanocrystals was performed by a nanoPET pharma GmbH with great reproducibility and homogenous size. In A549 cell cultures, the uptake and distribution of these nanocrystals within the monolayered cells was investigated by LA-ICP-MS measurements using subcellular resolution. The nanocrystals showed high sensitivity and the possibility of multiparametric analysis by doting different lanthanides. Additionally, stability of the bioconjugation of the nanocrystals and target antibodies was investigated using Dot Blot experiments and LA-ICP-MS.