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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Quantitative NMR-Spektroskopie als Referenzverfahren in der analytischen Chemie

Malz, Frank 10 July 2003 (has links)
Die Globalisierung von Handel und Wirtschaft macht es nötig, nationale Analysenergebnisse international gegenseitig anzuerkennen. Dabei kann die Richtigkeit der Analysenwerte durch Ruckführung auf Einheitsnormale mittels Primärmethoden, Zertifizierte Referenzmaterialien (ZRM) und Referenzverfahren gewährleistet werden. Die quantitative hochauflösende 1H-SP-NMR bietet sich aufgrund ihrer ausgezeichneten Selektivität und ihrem Potenzial als relative Primärmethode geradezu als Referenzverfahren an. Für vier wichtige Anwendungsbereiche (Bestimmung von Stoffmengenverhältnissen und -anteilen in mol/mol bzw. mol/mol %, der Reinheitsbestimmung über die Hauptkomponentenanalyse in g/g % und der Gehaltsbestimmung in mg/g) wurden anhand idealer Modellsysteme in Lösung (5-Komponenten: Ethyl-4-toluolsulfonat, [2,2]-Paracyclophan, Durol, Cyclododekan, Oktamethylcyclotetrasiloxan; Maleinsäure; 3-Trimethyl-2,2,3,3-tetradeuteropropionsäure-Natriumsalz (TSP)) die Messgleichungen und vollständigen Unsicherheitsbudgets aufgestellt sowie Arbeitsanweisungen zur quantitativen Aufnahme und Auswertung von 1H-NMR-Messungen erarbeitet. Dazu war für die Reinheits- und Gehaltsbestimmung ein System interner NMR-Standards aufzubauen (ZRM Benzoesäure, Maleinsäure, TSP-Lösung, Durol), das den Forderungen nach metrologischer Rückführung genügte. Zur Minimierung der Messunsicherheit wurden systematisch die Einflüsse gerätespezifischer Parameter und der Auswertung umfangreich untersucht und quantifiziert. Mittels mitorganisierter nationaler und internationaler CCQM-Ringversuche konnten allgemeingültige (unabhängig von der Gerätekonfiguration) Aussagen über die Messunsicherheit der Methoden bzw. Verfahren getroffen werden. Für realitätsbezogene Fragestellungen der Reinheitsbestimmung möglicher Referenzmaterialien für den pharmazeutischen Bereich (Spiraeosid, Thymol, Loganin) sowie von Xylol-Isomeren-Gemischen und der Gehaltsbestimmung 0,1%-iger wässriger Ethanollösungen mussten teilweise die quantitative 1H-entkoppelte 13C-NMR validiert und der quantitative Einsatz der 1H-Wasserunterdrückung (Presaturation) erstmalig entwickelt werden. Um die Güte der quantitativen NMR-Verfahren als Referenzverfahren bewertet zu können, wurde durch Beteiligung an internationalen Ringversuchen auf höchstem metrologischen Niveau (CCQM) deren Messunsicherheiten mit denen anderer analytischer Verfahren verglichen. Es konnten somit vier Referenzverfahren durch Dokumentation der Prüfbereiche, Messunsicherheiten und Einsatzgebiete der quantitativen hochauflösenden 1H- und 13C-NMR formuliert werden. / The globalisation of trade and economics makes requires mutual international recognition of analytical measurement results. The trueness of analytical results can be secured by establishing traceability to measurement standards for SI units using primary methods, certified reference materials (CRM) and reference methods. The quantitative high resolution 1H-SP-NMR offers itself as reference method due to its excellent selectivity and its potential as relative primary method. For four important areas of application (determination of amount-of-substance ratios and fractions in mol/mol and mol/mol %, respectively, purity determination by main component analysis in g/g %, and determination of minor component mass fractions in mg/g) the measuring equations and complete uncertainty budgets were set up, and work instructions for the acquisition and evaluation of quantitative 1H-NMR measurements were compiled, on the basis of ideal model systems in solution (5 components: Ethyl-4-toluenesulfonate, [2,2]-Paracyclophane, Durene, Cyclododecane, Octamethylcyclotetrasiloxane; Maleic acid; 3-Trimethyl-2,2,3,3-tetradeuteropropionic acid sodium salt (TSP)). In addition, a system of internal NMR standards had to be built up (CRM benzoic acid, maleic acid, TSP solution, Durene) for the determination of composition and purity, which meets the demands for metrological traceability. For the minimization of measurement uncertainty, the influences of instrument-specific parameters and data evaluation techniques were extensively examined and quantified. By means of national and jointly organized international CCQM intercomparisons generally applicable statements (independent of the measuring system configuration) about the measurement uncertainty for the different methods could be specified. For addressing real-life problems in purity determination of prospective reference substances for the pharmaceutical field (spiraeoside, thymol, loganin) as well as of xylene isomer mixtures and the analysis of 0,1 % aqueous ethanol solutions, the quantitative 1H-decoupled 13C-NMR had to be validated in part and the quantitative application of the 1H water suppression (presaturation) was developed for the first time. In order to estimate the power of quantitative NMR as a reference method, measurement uncertainties were compared with those of other analytical methods by participation in international intercomparisons on the highest metrological level (CCQM). Thus, four reference methods of the quantitative high resolution 1H- and 13C-NMR could be specified in terms of measuring ranges, measurement uncertainties and application fields.
2

Multivariate spectroscopic methods for the analysis of solutions

Wiberg, Kent January 2004 (has links)
<p>In this thesis some multivariate spectroscopic methods for the analysis of solutions are proposed. Spectroscopy and multivariate data analysis form a powerful combination for obtaining both quantitative and qualitative information and it is shown how spectroscopic techniques in combination with chemometric data evaluation can be used to obtain rapid, simple and efficient analytical methods. These spectroscopic methods consisting of spectroscopic analysis, a high level of automation and chemometric data evaluation can lead to analytical methods with a high analytical capacity, and for these methods, the term high-capacity analysis (HCA) is suggested. It is further shown how chemometric evaluation of the multivariate data in chromatographic analyses decreases the need for baseline separation. </p><p>The thesis is based on six papers and the chemometric tools used are experimental design, principal component analysis (PCA), soft independent modelling of class analogy (SIMCA), partial least squares regression (PLS) and parallel factor analysis (PARAFAC). The analytical techniques utilised are scanning ultraviolet-visible (UV-Vis) spectroscopy, diode array detection (DAD) used in non-column chromatographic diode array UV spectroscopy, high-performance liquid chromatography with diode array detection (HPLC-DAD) and fluorescence spectroscopy. The methods proposed are exemplified in the analysis of pharmaceutical solutions and serum proteins.</p><p>In Paper I a method is proposed for the determination of the content and identity of the active compound in pharmaceutical solutions by means of UV-Vis spectroscopy, orthogonal signal correction and multivariate calibration with PLS and SIMCA classification. Paper II proposes a new method for the rapid determination of pharmaceutical solutions by the use of non-column chromatographic diode array UV spectroscopy, i.e. a conventional HPLC-DAD system without any chromatographic column connected. In Paper III an investigation is made of the ability of a control sample, of known content and identity to diagnose and correct errors in multivariate predictions something that together with use of multivariate residuals can make it possible to use the same calibration model over time. In Paper IV a method is proposed for simultaneous determination of serum proteins with fluorescence spectroscopy and multivariate calibration. Paper V proposes a method for the determination of chromatographic peak purity by means of PCA of HPLC-DAD data. In Paper VI PARAFAC is applied for the decomposition of DAD data of some partially separated peaks into the pure chromatographic, spectral and concentration profiles. </p>
3

Multivariate spectroscopic methods for the analysis of solutions

Wiberg, Kent January 2004 (has links)
In this thesis some multivariate spectroscopic methods for the analysis of solutions are proposed. Spectroscopy and multivariate data analysis form a powerful combination for obtaining both quantitative and qualitative information and it is shown how spectroscopic techniques in combination with chemometric data evaluation can be used to obtain rapid, simple and efficient analytical methods. These spectroscopic methods consisting of spectroscopic analysis, a high level of automation and chemometric data evaluation can lead to analytical methods with a high analytical capacity, and for these methods, the term high-capacity analysis (HCA) is suggested. It is further shown how chemometric evaluation of the multivariate data in chromatographic analyses decreases the need for baseline separation. The thesis is based on six papers and the chemometric tools used are experimental design, principal component analysis (PCA), soft independent modelling of class analogy (SIMCA), partial least squares regression (PLS) and parallel factor analysis (PARAFAC). The analytical techniques utilised are scanning ultraviolet-visible (UV-Vis) spectroscopy, diode array detection (DAD) used in non-column chromatographic diode array UV spectroscopy, high-performance liquid chromatography with diode array detection (HPLC-DAD) and fluorescence spectroscopy. The methods proposed are exemplified in the analysis of pharmaceutical solutions and serum proteins. In Paper I a method is proposed for the determination of the content and identity of the active compound in pharmaceutical solutions by means of UV-Vis spectroscopy, orthogonal signal correction and multivariate calibration with PLS and SIMCA classification. Paper II proposes a new method for the rapid determination of pharmaceutical solutions by the use of non-column chromatographic diode array UV spectroscopy, i.e. a conventional HPLC-DAD system without any chromatographic column connected. In Paper III an investigation is made of the ability of a control sample, of known content and identity to diagnose and correct errors in multivariate predictions something that together with use of multivariate residuals can make it possible to use the same calibration model over time. In Paper IV a method is proposed for simultaneous determination of serum proteins with fluorescence spectroscopy and multivariate calibration. Paper V proposes a method for the determination of chromatographic peak purity by means of PCA of HPLC-DAD data. In Paper VI PARAFAC is applied for the decomposition of DAD data of some partially separated peaks into the pure chromatographic, spectral and concentration profiles.

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