Analytische Chemie
Filtern
Dokumenttyp
- Buchkapitel (52) (entfernen)
Schlagworte
- Archaeometry (4)
- ICP-MS (4)
- Zerstörungsfreie Prüfung (4)
- Archäometrie (3)
- Concrete (3)
- Dead Sea Scrolls (3)
- Fluorescence (3)
- Imaging (3)
- Non-destructive testing (3)
- Structural health monitoring (3)
Organisationseinheit der BAM
- 4 Material und Umwelt (12)
- 4.5 Kunst- und Kulturgutanalyse (11)
- 8 Zerstörungsfreie Prüfung (11)
- 1 Analytische Chemie; Referenzmaterialien (8)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (5)
- 6 Materialchemie (4)
- 1.4 Prozessanalytik (3)
- 1.1 Anorganische Spurenanalytik (2)
- 6.6 Physik und chemische Analytik der Polymere (2)
- 7 Bauwerkssicherheit (2)
The one-phase methods described in Chapter 2 were shown to be able to predict casting to some extent, but could not depict segregation, sedimentation and blockage occurring during flow. On the other hand, the distinct element methods described in Chapter 3 did not take into account the presence of two phases in the system and describes concrete as distinct elements interacting through more or less complex laws. A reliable numerical model of a multiphase material behaviour shall take into account both phases (solid and liquid). From the numerical point of view, concrete flow shall be seen therefore as the free surface flow of a highly-concentrated suspension of rigid grains.
Biosensors, as defined by Pure and Applied Chemistry, are ‘chemical sensors in which the recognition System utilizes a biochemical mechanism. The biological recognition system translates information from the biochemical domain, usually an analyte concentration, into a chemical or physical output signal with a defined sensitivity’.(1) It is also appointed that chemical or biological sensors contain two basic components connected in series: a chemical or biomolecular recognition System (receptor) and a physicochemical transducer. According to this prerequisite, this overlook is confined to sensor devices that combine a biomolecular recognition element with an optical signal transducer. Homogeneous or intracellular assays using fluorescent molecular probes or nanoparticles are not considered, although they are frequently termed as molecular sensors or nanosensors in the literature.
Fluorescence-based biosensors are generalized as those devices that derive an analytical signal from a photoluminescent (either fluorescence or phosphorescence) emission process. Chemi- or bioluminescent detection systems are only briefly discussed in this review.
Biosensors are used for a wide variety of tasks, including detection of compounds of biomedical, environmental or defense interest; on-line monitoring for process control; quality control of foodstuffs; selective detection of compounds undergoing a chemical separation; and screening of drug compounds. Advantages of such devices include high selectivity, rapid response times, reusability, amenability to remote analysis, and immunity to electrical interferences. The selective nature of complexation between biomolecule and analyte and the small size of sensor devices can be combined with advanced detection techiques such as total internal reflection (TIR) spectroscopy. This results in an ability to measure analytes in complex matrices with unsurpassed sensitivity. Such samples may include highly scattering components such as milk or whole blood,(11) or relatively inaccessible locations such as groundwater wells, or even intracellular environments. The key limitation of such devices mainly centers on the poor stability of biological compounds, which can lead to a substantial drift in instrumental response over time. The so-called Cambridge Definition appoints another characteristic property of sensors. Therein, they are defined as ‘miniaturized devices which can deliver real-time and on-line information on the presence of specific compounds or ions in even complex samples’. Accordingly, a sensor is expected to respond reversibly and continuously. With the exception of some enzymatic sensors, these conditions are not fulfilled in case of most biosensors. Particularly, in devices where immunological reagents or DNA are used as recognition elements, they show a lack of reversibility and operate only as a ‘one-shot’ screen, without the potential for continuous, quantitative analysis. Nevertheless, the designations immunosensors or DNA sensors became accepted for such analytical or diagnostic tools.
The investigation of cultural assets often deals with the question of provenance, dating, or attribution to artists or workshops. The analysis of physical properties and chemical composition generates important data for answering cultural-historical questions that cannot be solved by stylistic and art-historical methods alone. Starting from some wooden painted architectural elements from Kocho and one from Bezeklik (III 8592), this paper aims to give some insights into the multi-instrumental approach to the analysis of cultural artefacts.
In the present chapter, the capabilities of Raman spectroscopy for the advanced characterisation of thin films for solar cells are reviewed. Raman spectroscopy is an optical, nondestructive technique based on the inelastic scattering of photons with elemental vibrational excitations in the material. The line shape and position of the Raman bands are determined by the crystalline structure and chemical composition of the measured samples, being sensitive to the presence of crystalline defects, impurities and strain. Presence of peaks characteristic of different phases also allows for the identification of secondary phases that are strongly related to the growth and process conditions of the films. All these aspects account for a strong interest in the analysis of the Raman spectra, providing a powerful nondestructive analytical tool for the structural and chemical assessment of the films. In addition, the combination of a Raman spectrometer with an optical microscope also allows for achieving a high spatial resolutions (of below 1 µm) when mapping surfaces and analyzing depth-resolved phase distributions in thin films.
The present chapter is divided into four main sections: The two first ones are devoted to a revision of the Fundamentals of Raman spectroscopy (Section 17.2) and Vibrational modes in crystalline materials (Section 17.3). Section 17.4 deals with the main experimental considerations involved in the design and implementation of a Raman scattering setup. This is followed by a detailed description of the application of Raman scattering for the structural and chemico-physical analysis of thin film photovoltaic materials (Section 17.5), with the identification of crystalline structure and secondary phases, evaluation of film crystallinity, analysis of chemical composition of semiconductor alloys, characterisation of nanocrystalline and amorphous layers, stress effects and crystal orientations. This includes the description of corresponding state of the art and recent case examples that illustrate the capabilities of the Raman technique for the advanced characterisation of layers and process monitoring in thin-film photovoltaic technologies.
The chapter describes the application of electronic noses (multigas sensors) for the quality control of spices and spice mixtures. Electronic noses were successfully applied for headspace analysis of spices. It was demonstrated in many investigations that electronic noses can contribute to the characterization of spices and spice mixtures in order to distinguish spices and spice mixtures, differentiate by origin, growth seasons,and processing,indicate adulteration from original, detect mold infestation. Electronic noses can be used as a fast screening method to provide information about the product quality. However, it needs samples and methods for reference, careful training, and complex calibration to consider influencing and disturbing effects as well as the possible limitations of the instrumentation. The correlation to classical chemical analysis methods is always advisable. Machined olfaction methods are capable to support the sensory analysis; however, they cannot yet substitute them.
An ideal sensor system is a combination of a selective receptor, an effective transducer, and a sensitive detector. To utilize molecularly imprinted polymers (MIPs) as responsive recognition phases in sensors, the employment of fluorescent molecules or nanoparticles (NPs) that show prominent changes in their spectroscopic properties after binding of the target molecule in the MIP’s cavity is particularly attractive. Such fluorescent MIPs (fMIPs) act through target-induced quenching, enhancement, or spectral shifts of the fluorescence. This contribution introduces different strategies of incorporation of fluorescent dyes, probes, and NPs into fMIPs. In addition, various sensing mechanisms are reviewed, and depending on the application of the sensor, the different deployable formats, their advantages, drawbacks, and impact will be presented and discussed.
The investigation of physical properties and chemical composition generates data important for answering art-historical questions. Due to technological developments, technical diagnostics in art and culture are in ever-greater demand in such fields of transdisciplinary research. Based on one example, a collar drawing from the Berlin Diez albums, the present paper aims to give some insights into the multi-instrumental approach in the material analysis of cultural artefacts. The same methods were also applied to other drawings from the Diez Albums.
Seit 2009 entsteht die historisch-kritische Hybridediton von Goethes „Faust“. Im Januar 2013 ist im Rahmen dieses editorischen Unternehmens die Röntgenfluoreszenzanalyse (RFA) zum Einsatz gekommen, um auf der Grundlage der Zusammensetzung der verwendeten Eisengallustinten entstehungsgeschichtliche Erkenntnisse über das handschriftliche Material zu gewinnen. Im Mittelpunkt stand neben der zeitlichen Einordnung von Handschriften vor allem die Identifikation von unterscheidbaren Bearbeitungsschichten innerhalb der jeweiligen Handschrift. Besonderes Interesse kommt dabei denjenigen Handschriften zu, von denen sicher ist oder angenommen wird, dass Goethe sie über längere Zeit hinweg oder sogar in sehr großen Abständen bearbeitet hat.
Die von der traditionellen Philologie in Anschlag gebrachten äußeren und inneren Gründe und die darauf gestützten Hypothesen haben nicht ausgedient. Hypothesen zur Datierung von Handschriften Goethes lassen sich in der Regel gut anhand bestehender materieller Zusammenhänge (wie der Zuordnung des Papiers in Kombination mit der Bestimmung der Schreiberhand) verifizieren. Dagegen ermöglicht materialwissenschaftliche Charakterisierung der Eisengallustinten alleine zunächst noch keine vergleichbar genauen Datierungen. Eine Kombination der beiden Zugänge und Verfahren kann jedoch dort Erkenntnisse zutage fördern, wo die traditionellen philologischen Mittel ausgeschöpft sind. Dies wird exemplarisch innerhalb der Publikation gezeigt werden.