Analytische Chemie
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Remote gas sensors mounted on mobile robots enable the mapping of gas distributions in large or poorly accessible areas. A challenging task however, is the generation of three-dimensional distribution maps from these spatially sparse gas measurements. To obtain high-quality reconstructions, the choice of optimal measuring poses is of great importance. Remote gas sensors, that are commonly used in Robot Assisted Gas Tomography (RAGT), require reflecting surfaces within the sensor’s range, limiting the possible sensing geometries, regardless of whether the robots are ground-based or airborne. By combining ground and aerial robots into a heterogeneous swarm whose agents are equipped with reflectors and remote gas sensors, remote inter-robot gas measurements become available, taking RAGT to the next dimension – releasing those constraints. In this paper, we demonstrate the feasibility of drone-to-drone measurements under realistic conditions and highlight the resulting opportunities.
Sediments and soils can act as sinks of species of inorganic mercury (Hg2+), while they are simultaneously sources of organic species, such as monomethylmercury (MMHg). Although the fraction of MMHg in total Hg of sediments is suggested to be only 0.1–1%, MMHg poses a threat for humans and wildlife due to its toxic properties, high bioaccumulation potential and the ability to pass the blood-brain barrier. One example of a highly Hg contaminated waterbody is the Finow Canal, the oldest artificial waterway still in operation in Germany. Here, Hg mass fractions of up to 100 µg/g were found in the sediment in previous studies. These are suggested to be associated with a chemical plant producing mercury-based seed dressings. Despite this high mass fraction of Hg, no Hg speciation studies have been conducted there up to now.
In this study, Hg speciation in sediments of Finow Canal at locations before and after the known polluted site was conducted using species-specific isotope dilution (SSID) GC-ICP-ToF-MS. Mass fractions of up to 0.41 µg/g MMHg were determined. In addition, waterbodies around the initially polluted site were investigated and elevated concentrations were also determined around 14 km downstream. For MMHg analysis, the performance of ICP-ToF-MS for SSID GC/ICP-MS was compared with ICP-Q-MS and ICP-SF-MS. Here, isotope ratio precision was similar between the tested instruments. However, the (quasi-) simultaneous detection of the whole mass spectrum will probably offer a much higher precision of ICP-ToF-MS, when more than one isotope system is used.
These results are the first evidence of the occurrence of MMHg in this region and show the need for further investigations of the whole regional ecosystem, as well as the consideration of possible measures of remediation. SSID GC-ICP-(ToF)-MS is a suitable tool for investigating species-specific (multi) isotope systems for environmental monitoring.
Wasserstoff als flexibel einsetzbarer und leicht transportierbarer Energieträger bildet eine Schlüsselkomponente auf dem Weg zu einer klimaneutralen Energiewende. Zur Speicherung von gasförmigem Wasserstoff kommen bei stationären und auch mobilen Anwendungen meist Druckbehälter aus Verbundwerkstoffen zum Einsatz. Dabei ist für den Betrieb der Behälter die Gewährleistung der Sicherheit von großer Relevanz. Structural Health Monitoring (SHM) bietet einen innovativen Ansatz, um sowohl die Sicherheit als auch die Zuverlässigkeit der Druckbehälter zu gewährleisten und kritische Versagensfälle zu vermeiden.
Zur kontinuierlichen Überwachung und Bewertung des Zustands eines Wasserstoffdruckbehälters wird in dem vorliegenden Beitrag eine aktive Methode präsentiert, die auf geführten Ultraschallwellen basiert. Dabei kommt das Pitch-Catch Verfahren zwischen Sender und Empfängern zur Überwachung der strukturellen Integrität zum Einsatz. Auf Grundlage des untersuchten Wellenausbreitungsverhaltens im Druckbehälter sowie der Geometrieeigenschaften wird ein Sensornetzwerk aus piezoelektrischen Flächenwandlern (PZT) zur Abdeckung des zu überwachenden Bereichs entworfen. Ziel ist es mit Hilfe eines Optimierungsalgorithmus eine größtmögliche Abdeckung bei gleichzeitiger Minimierung der Anzahl der Sensoren zu erreichen. Zudem soll eine gleichmäßige und platzsparende Verteilung im Vordergrund stehen, so dass zukünftig weitere Messmethoden auf dem Druckbehälter angewendet werden können (z. B. durch akustische oder faseroptische Sensoren).
Das für die Anwendung optimierte Sensornetzwerk wird anschließend hinsichtlich der Robustheit bei der Schadenserkennung und -lokalisierung durch Aufbringen von künstlichen Schäden evaluiert. Die Ergebnisse zeigen, dass die künstlichen Schäden am Wasserstoffdruckbehälter nachgewiesen werden können.
Rapid tests and assays to be used outside of a laboratory for non-trained personal and also at a point of need are becoming increasingly important in areas such as health, food, security, or the environment. Specially on that regard, paper-based sensors are emerging as a new class of devices because they fulfil the requisites of the "World Health Organization" to be ASSURED: affordable, sensitive, specific, user-friendly, rapid and robust, equipment free and deliverable to end-users. The physical, chemical and mechanical properties of cellulose or glass fiber paper in combination with the facility of preparation are making these materials of great interest while looking for cost-efficient and green alternatives for device production technologies. To improve the sensitivity of these systems, a particularly promising approach is the employment of gated indicator delivery systems using preorganized nanoscopic solid structures incorporated on paper strips to produce an exponential amplification of the detectable signal. Having in mind these concepts, several examples of (bio)gated materials incorporated into sensing membranes will be presented for the detection of small organic molecules, having fluorescence or electrochemiluminescence signal as output signal. Compared with fluorescence, it has been demonstrated that the non-optical excitation has significantly reduced the background signal, and with the help of a portable potentiostat in combination with a home-made 3D-printed case fitted onto a smartphone, the sensitivity of the sensing system has been improved tremendously, from the lower ppb range (fluorescence) to the lower ppt range. With this study, the applicability of ECL detection on paper strips in combination with gated indicator-releasing materials has been demonstrated for the first time, presenting a novel synergistic match. Considering the modularity of the system developed, the platform technology potential is obvious, promising expansion of the general concept to many other analytes, applications and scenarios.
Since several years, magnetic sensor elements are available in fully flexible architectures that often reveal identical sensing properties, compared to their rigid counterparts, while being bent severely and repeatedly. Nowadays, a variety of magnetic senor principles, including well known Hall, AMR and GMR but also more exotic PHE and AHE sensors were demonstrated on such flexible platforms. The novel properties of being thin, lightweight, shapeable, and wearable enable magnetic sensory systems to be utilized in vicinities and conditions that are inaccessible for rigid and microchip-based sensors.
Ultrasonic coda wave interferometry can detect small changes in scattering materials like concrete. We embedded ultrasonic transducers in the Gänstorbrücke Ulm, a monitored road bridge in Germany, to test the methodology. Since fall 2020, we've been monitoring parts of the bridge and comparing the results to commercial monitoring systems. We calculate signal and volumetric velocity changes using coda waves, and long-term measurements show that the influence of temperature on strains and ultrasound velocity changes can be monitored. Velocity change maps indicate that different parts of the bridge react differently to environmental temperature changes, revealing local material property differences. A load experiment with trucks allows calibration to improve detectability of possibly damaging events. Our work focuses on measurement reliability, potential use of and distinction from temperature effects, combination with complementary sensing systems, and converting measured values to information for damage and life cycle assessment.
Die PKI zum digitalen Akkreditierungssymbol der DAkkS sowie dessen Funktionsweise und daraus resultierende Mehrwerte für Kalibrierlaboratorien und Endanwender werden vorgestellt. Im Anschluss wird der aktuelle Stand bei der Einführung des digitalen Kalibrierscheins (DCC) im akkreditierten Kalibrierlabor der BAM wiedergegeben. Eine Roadmap für die Digitalisierung des Kalibrierlabors sowie die Vorstellung des Quality-X Konzeptes geben einen Ausblick in die nähere Zukunft.
The reference method for obtaining absolute isotope ratios still is the isotope mixture approach. Due the huge efforts required the full isotope mixture approach is applied only by a few institutes worldwide. To enable an IRWG key comparison with a sufficiently large number of participants a proposal for absolute cu isotope ratios is presented where participants will be provided with the enriched isotopes, the isotope mixtures and the samples. In parallel a pilot study will be organized where alternative approaches for obtaining absolute Cu isotope ratios can be applied.