Analytische Chemie
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Eingeladener Vortrag
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The evaluation of measurement uncertainty is essential for testing and calibration laboratories. This paper provides a general process description for the determination of the measurement uncertainty of quantitative data and its application to the conformity assessment with examples, and how to deal with the uncertainty of qualitative (Boolean) results, e. g. when "Alarm" or "No alarm" occours in an instrument display.
Monodisperse iron oxide nanoparticles as reference material candidate for particle size measurements
(2020)
In order to utilize and rationally design materials at the nanoscale the reliable characterization of their physico-chemical properties is highly important, especially with respect to the assessment of their environmental or biological impact. Furthermore, the European Commission’s REACH Regulations require the registration of nanomaterials traded in quantities of at least 1 ton. Powders or dispersions where 50% (number distribution) of the constituent particles have sizes ≤ 100 nm in at least one dimension are defined as nanomaterials. This creates a need for industrial manufacturers and research or analytical service facilities to reliably characterize potential nanomaterials. Currently, BAM is developing reference nanoparticles, which shall expand the scarce list of worldwide available nano reference materials certified for particle size distribution and will also target other key parameters like shape, structure, porosity or functional properties. In this respect, materials like iron oxide or titanium dioxide are considered as candidates to complement the already available silica, Au, Ag, and polystyrene reference nanoparticles.
The thermal decomposition of iron oleate precursors in high boiling organic solvents can provide large quantities of iron oxide nanoparticles that can be varied in size and shape.[1, 2] The presence of oleic acid or other hydrophobic ligands as capping agents ensures stable dispersion in nonpolar solvents. Such monodisperse, spherical particles were synthesized at BAM and pre-characterized by electron microscopy (TEM, SEM including the transmission mode STEM-in-SEM) and dynamic light scattering comparing cumulants analysis and frequency power spectrum.
1. REACH regulations and nanosafety concerns create a strong need for nano reference materials with diverse properties.
2. Iron oxide nanoparticles are under development as new candidate reference material at BAM.
3. Narrow particle size distribution confirmed by light scattering and electron microscopy.
In the face of rising energy demand and the impending climate change the development of a sustainable, fossil-free fuel and chemical production is of global importance. One possible goal is the development of electrochemical conversion processes using catalysts. Porous materials play an important role in such energy applications. The key to the development of improved catalysts is a better understanding of the relations between their performance, stability and physico-chemical properties. However, the complex morphology of such catalysts constitutes a challenge even for modern analytical techniques.
Spectroscopic ellipsometry (SE) is a versatile method for studying material properties by using appropriate models (e.g. film thickness, optical and electronic properties). The fact that the material properties cannot be taken directly from the measured spectra, the developed models have to be validated. In a first step, the model for the ellipsometric fit studies of a calcination series of mesoporous iridium oxide films (300 – 600 °C) was investigated and validated with respect to their material properties. Moreover, the electronic structures of the catalysts reveal a direct correlation with electrochemical activities. The development of an environmental cell offers the possibility of investigations under real conditions. This will allow changes in the optical and electronic properties during the electrocatalytic oxygen evolution reaction.
The progress in activities on Microbeam Analysis under VAMAS/TWA 37 is reviewed. Particularly the liaison with the new projects within the ISO technical committee TC 202 is presented and discussed with respect to the possibility of identifying and launching related VAMAS projects. Need of more promotion for the engagement of more participants from industry and academia at national, European and international level is highlighted. Also, the competition with the other technical working areas (on 'nano' or materials-related) is critically discussed.
Um die Versagensabläufe über die verschiedenen Skalen im Holzwerkstoff verfolgen zu können, werden Zugversuche an Lagenhölzern mittels Schallemissionsmessung überwacht. Synchron erfolgen In-situ-Messungen mit Digitaler Bildkorrelation bzw. Synchrotron-Mikro-Computertomographie. Die Kombination aller Ergebnisse wie auch die Anwendung der frequenzbasierten Mustererkennung und die Simulation ausgewählter Versuche zielen auf die Identifizierung zugrunde liegender Mechanismen hin. Abschließend werden Ansätze für ein Monitoring von Holzstrukturen diskutiert.
Toxic secondary metabolites produced by fungi (aka mycotoxins) are often identified as contaminants in cereals or other food and pose a severe health risk, since they can be carcinogenic, neurotoxic, mutagenic or harmful in other respect. The highly nephrotoxic ochratoxin A (OTA) is one of the most important and widespread mycotoxins found in grains such as rye, wheat or oats. Thus, the fast and cost-effective detection of OTA is of great importance, to ensure that the toxin concentration is below the legal limits. Currently, the mycotoxin detection in mill operations is typically performed by means of the antibody-based ELISA method, which requires extensive laboratory equipment and specialized personnel. It was the aim of this study to develop an ELISA-inspired sensor method enabling the on-site quantification of OTA. Based on a classical competitive ELISA, an electrochemical detection system was developed. Anti-OTA-antibodies were captured on magnetic beads on which the competitive affinity reaction between OTA and an OTA- horseradish peroxidase (HRP) tracer was performed. Here the OTA concentration is inversely proportional to the amount of the bound OTA-HRP tracer, which was electrochemically quantified. For this purpose, oxidized tetramethylbenzidine (TMB), which is enzymatically produced by the reduction of H2O2 by the OTA-HRP tracer, is quantified by amperometry with screen-printed electrodes in a flow system. With this method a detection limit of 250 ng L-1 could be achieved which meets the current requirements for the detection of OTA in food and feed.
In the wake of digitalization, organizations are increasingly exposed to risks associated with security breaches and must take measures to preserve the confidentiality, integrity, and availability of information, and to ensure business continuity. The international standard ISO/IEC 27001 assists organizations in setting up, maintaining and continuously improving their information security management systems. However, despite high growth rates, its international diffusion rates are quite heterogeneous. This paper explores why the diffusion of the international management system standard ISO/IEC 27001 differs across countries. We classify the adoption of ISO/IEC 27001 as a ‘preventive organizational innovation’ and draw from diffusion studies of other management system standards and information security research to develop a set of hypotheses. These relate to the impact of cultural dimensions and national ICT development. We use a negative binomial regression model with panel data covering 57 countries over a 12-year period from 2006 to 2017 to test our hypotheses. We find that the cultural dimensions future orientation, power distance, and institutional collectivism as well as high ICT development are driving factors for the diffusion of ISO/IEC 27001. We derive policy recommendations and avenues for future research.
In many scientific fields, isotopic analysis can offer valuable information. Up to date, typically bulk analysis is aimed at measuring the isotopic composition of the entire elemental content of the sample. However, the analyte element is usually present under the form of different species. Thus, separating species of interest from one another and from matrix components prior to isotope ratio measurements can provide species-specific isotopic information, which could be used for tracing the origin of environmental pollutants and elucidation of (environmental) speciation. Using on-line hyphenations of separation techniques with multicollector-ICP-MS (MC-ICP-MS) can save time and effort and enables the analysis of different species during a single measurement. Whereas some works hyphenating GC and IC with MC-ICP-MS have already been reported, LC and CE hyphenations are still inadequately represented based on the capabilities of these separation techniques.
In this work, we developed an on-line hyphenation of CE with multicollector-ICP-MS (CE/MC-ICP-MS) for isotopic analysis of sulfur species using a multiple-injection approach for instrumental mass bias correction by standard-sample bracketing. With this method, the isotopic composition of sulfur in sulfate originating from river water could be analyzed without sample preparation. The results were compared to data from off-line analysis of the same samples to ensure accuracy. The precision of the results of the on-line measurements was promising regarding the differentiation of the river systems by the isotopic signature of river water sulfate. The great potential of this method is based on the versatility of the applied separation technique, not only in the environmental field but also for, e.g., biomolecules, as sulfur is the only covalently bound constituent of proteins that can be analyzed by MC-ICP-MS.
Entwicklung eines luftgekoppelten Ultraschall-Echo-Prüfverfahrens mittels fluidischer Anregung
(2020)
In vielen technischen Bereichen werden Ultraschallverfahren zur zerstörungsfreien Werkstoffprüfung (ZfP) eingesetzt um auf Basis der Signalstärke und der Laufzeit Einbauteile und Beschädigungen zu orten. Luftgekoppelter Ultraschall spielt bisher in kommerziellen Anwendungen vor Allem im Bauwesen eine untergeordnete Rolle, da die Differenz der akustischen Impedanzen von Luft und Festkörpern immense Verluste beim Übergang des Schallsignals hervorruft.
Im Rahmen des Promotionsvorhabens soll die Eignung eines neuartigen Anregungsprinzip untersucht werden, mit dem ein Großteil dieser Verluste vermieden werden soll. Anstelle eines Festkörpers soll mit Hilfe einer fluidischen Düse Druckluft zur Signalerzeugung eingesetzt werden. Die Impedanzverluste zwischen Aktuatormembran und Umgebungsluft entfallen daher.
Die gezielte Schallerzeugung durch einen pulsierenden Freistrahl ist weitgehend unerforscht. Es ist daher notwendig, den so erzeugten Schallpuls in der Interaktion mit dem transienten Strömungsfeld zu untersuchen. Das kompressible Medium Luft und die geringen räumlichen Dimensionen einer hochfrequenten Pulsdüse werfen darüber hinaus einige Herausforderungen hinsichtlich der eingesetzten Messtechnik auf. Hier sollen geeignete Verfahren weiterentwickelt und validiert werden, um die Eignung des fluidisch erzeugten Pulses zu überprüfen.
In diesem Vortrag werden erste Messungen an einem fluidischen Schalter mit denen an einem kommerziellen Luftultraschallprüfkopf verglichen.