521 |
Trace analysis by molecular spectroscopyZeng, Zuotao January 2001 (has links)
This thesis describes new analytical methods for trace or ultra-trace analysis by molecular absorption and emission spectroscopy. The initial part of the thesis is devoted to an introduction to molecular electromagnetic absorption spectroscopy and molecular fluorescence. The principles, advantages and limitations of spectrophotometric and fluorimetric measurement are discussed. The concepts of enzymes and their applications in analytical chemistry are also expounded. Two organic compounds, 5-( 4-arsonophenylazo )-8-(p-toluenesulfonamido)quinoline (APTSQ) and 5-(p-methoxyphenylazo)-8-(p-toluenesulfonamido) quinoline (MPTSQ), have been synthesised and used as new chromogenic anellor f1uorogenic reagents. Five specific, highly sensitive, simple, precise and inexpensive novel analytical methods have been developed: (1) A spectrophotometric method is described for the determination of cobalt. The maximum absorbance is at 582 nm with a molar absorptivity of 1.18 x 1 as I mor' cm-1 . Beer's law is obeyed for cobalt concentrations in the range 0-0.5 J.l.g mr'. (2) A fluorimetric method for the determination of cobalt is proposed. The fluorescence intensity is measured at Aex 287 nm and Aem 376 nm. The response is linear up to 25 ng mr' and the detection limit is 0.002 ng mr'. The mechanism of the fluorescence reaction has been investigated. (3) A flu~ri~etric method is proposed for the d~ter~i~~tion of H202. The response IS linear up to 12.2 ng mr H:t>2. The detection limit IS 0.16 ng mr'. (4) An enzymatic assay for glucose by spectrofluorimetry is described. The fluorescence intensity is proportional to the concentration of glucose up t0180 ng mr'. A detection limit of 5.4 ng mr' was obtained and allowed the determination of glucose in an extremely small amount of serum (O.5J.1.I) and urine (1 J.l.1). (5) A fluorimetric method for the determination of iron is proposed, based on the reaction between iron(III) and MPTSQ in the presence of cetyltrimethylammonium bromide. The fluorescence intenSity (Aex=317 nm, A.em=534 nm) is linear up to 170 ng mr' with a detection limit of 0.12 n9 mr'. An investigation of the mechanism of the fluorescence reaction has been made. The applications of the proposed methods for the determination of the concerned analytes at low levels in biological, environmental, pharmaceutical or beverage samples are also reported.
|
522 |
Raman microscopic and computational studies of artists' pigments and molecular inorganic compoundsBrown, Katherine Louise January 2002 (has links)
This thesis is principally concerned with spectroscopic and computational studies of artists' pigments. Manuscripts, art and archaeological artefacts were examined by Raman microscopy, identifying the pigments and drawing conclusions for historical and conservation purposes. Studies of Anglo Saxon and later manuscripts have shown the Insular palette triumvirate, assumed to be orpiment, red lead and verdigris, to contain red ochre and vergaut, but no verdigris. This remains unchanged until the introduction of lazurite in c. 920 AD and vermilion in the 12th century. Lazurite has been erroneously identified on the Lindisfarne Gospels, by the technique of Roosen-Runge. Raman microscopy shows the blue pigments to be exclusively indigo, casting doubt on analyses performed using Roosen-Runge's technique. The Islamic manuscript palette was found to be remarkably consistent across a substantial geographical area over an extended period. It is also very similar to that of early Western manuscripts. Comparison of these results with existing literary sources has shown the latter to be highly inaccurate. The palette of William Blake was examined and compared to results of analysis by False Colour Infrared Photography (FC-IP). The FC-IP technique was determined to be inappropriate for pigment identification. Two significant artefacts were shown to be modern forgeries: a rare Assyrian fresco contains a modern green pigment, and the world famous Vinland map was found to have significant quantities of anatase in the yellow lines. Density Functional Theory methods were applied to the mechanism of decay isomerisation of As4S4, which was partially clarified, and to the geometries of R2SeX2 (R = CF3, CF2H, CFH2, CH3, CH2CH3, CH(CH3)2, t-Butyl, X=F, Cl, Br, I, At). The most stable geometry was found to be determined by the polarity of the Se-X bonds and the steric and electron-withdrawal effects of the R-group on the C-Se bond strength.
|
523 |
Paper-based potentiometric platforms for decentralised chemical analysisNovell Recasens, Marta 16 September 2015 (has links)
En les darreres dècades, el món ha experimentat profunds canvis socials i tecnològics. Entre aquests, són destacables les tendències emergents d’anàlisis descentralitzats i de xarxes de sensors, que estan tenint un gran impacte en moltes àrees, especialment en el sistema sanitari. El desenvolupament d’eines per a realitzar anàlisis fora del laboratori de forma robusta, simple i econòmica, serà de gran ajuda per generar, per exemple, eines de diagnòstic assequibles. Per complementar aquestes tendències, aquesta tesis presenta el desenvolupament d’una eina analítica nova per anàlisis descentralitzats, usant paper modificat amb nanotubs de carboni com a substrat i la potenciometria com a tècnica de detecció. Els nanotubs de carboni s’han incorporat amb èxit sobre un paper de filtre convencional, convertint-lo així en conductor, i proporciona’t-li habilitat transductora ió-electró. Amb aquesta plataforma s’han desenvolupat elèctrodes selectius de ions per a diferents ions –mantenint el mateix rendiment analític que els elèctrodes convencionals- així com també un elèctrode de referència. La demostració de que aquesta plataforma pot solucionar un problema analític s’ha dut a terme a través del desenvolupament d’una cel·la potenciomètrica complerta de paper per a la detecció de liti en sang. Aquests elèctrodes també han estat combinats amb èxit amb un potenciòmetre d’identificació per radiofreqüència (RFID), cosa que permet el seu ús de forma descentralitzada. Altres aplicacions possibles, juntament amb les limitacions del sistema es discuteixen en detall. En definitiva, aquest treball obre la possibilitat de substituir sensors convencionals per aquesta plataforma més econòmica, obrint així tota una nova gama d’oportunitats. / En las últimas décadas, el mundo ha experimentado profundos cambios sociales y tecnológicos. Entre los cuáles son destacables las tendencias emergentes de análisis descentralizados y de redes de sensores, que tienen un gran impacto en muchas áreas, especialmente en el sistema sanitario. El desarrollo de herramientas para realizar análisis fuera del laboratorio de forma robusta, simple i económica, será de gran ayuda per generar, para generar, herramientas de diagnóstico asequibles. Para complementar estas tendencias, esta tesis presenta el desarrollo de una herramienta analítica nueva para análisis descentralizados, usando papel modificado con nanotubos de carbono como sustrato y la potenciometría como técnica de detección. Los nanotubos de carbono se han incorporado con éxito sobre un papel de filtro convencional, convirtiéndolo así en conductor, y proporcionándole habilidad transductora ion-electrón. Con esta plataforma se han desarrollado electrodos selectivos de iones para distintos iones manteniendo el mismo rendimiento analítico que los electrodos convencionales- así como también un electrodo de referencia. La demostración de que esta plataforma puede solucionar un problema analítico se ha hecho a través del desarrollo de una celda potenciométrica completa de papel para la detección de liti en sangre. Estos electrodos también se han combinado con éxito con un potenciómetro de identificación por radiofrecuencia (RFID), cosa que permite su uso de forma descentralizada. Otras aplicaciones posibles, junto con las limitaciones sistema se discuten en detalle. En definitiva, este trabajo abre la posibilidad de substituir los sensores convencionales por esta plataforma más económica, abriendo así tota una nueva gama de oportunidades. / During the last decades, the world has undergone deep social and technological changes. Remarkably are the emerging trends of decentralised analysis and sensing networks, which are having a deep impact in many areas, especially in the healthcare system. The development of tools for performing measurements out of the lab in a robust, simple and cost-effective way will be of great help to generate, for example, affordable diagnostic tools. To complement this trends, this thesis presents the development of a novel analytical tool for decentralised measurements, by using paper as a substrate modified with carbon nanotubes (CNT), and potentiometry as detection approach. CNTs have been successfully incorporated over a conventional filter paper making it conductive, and giving to it ion-to-electron transduction capability. Over this platform ion-selective electrodes for different ions have been developed –keeping the same analytical performance as conventional electrodes- as well as a reference electrode. The demonstration that this platform can solve an analytical problem has been proved through the development of a complete paper cell for the detection of lithium in blood. This electrodes have been also combined with a radio frequency identification (RFID) potentiometer, which will allows its use in a decentralised way. Other possible application of this platform together with its limitations are also discussed. All in all, this work opens the possibility to substitute conventional sensors for this low-cost paper sensors, thus unlocking a whole new range of possibilities.
|
524 |
Diseño y síntesis de receptores multicanal basados en 1,1´- ferroceno disustituidosSola Robles, Antonia María 29 June 2015 (has links)
Uno de los retos que, desde hace unos años, viene afrontando la Química actual es la relacionada con el desarrollo de métodos que permitan la detección de forma efectiva, sensible, selectiva y en tiempo real de sustancias responsables de la contaminación ambiental o de aquellas que están implicadas en procesos biológicos y clínicos. Por consiguiente, no es de extrañar que a lo largo de las últimas décadas, uno de los campos de investigación más activos lo constituya el dedicado al desarrollo de sensores químicos de este tipo de especies. En este contexto, los principales objetivos de esta Tesis están dirigidos al diseño, síntesis y estudio de moléculas, estructuralmente sencillas, capaces de comportarse como sensores moleculares, tanto para aniones como cationes. Para este fin, los receptores sintetizados deben contener dos partes básicas: una unidad de reconocimiento y una unidad de señalización que permita observar el fenómeno de reconocimiento a través de un cambio en las propiedades del receptor (electroquímicos, colorimétricos o fluorescentes). A pesar del desarrollo de sensores ópticos o electroquímicos para la detección de aniones o cationes, el uso de sensores multicanal para la detección de aniones es poco habitual. Por lo tanto, el trabajo contenido en esta Tesis está centrado en conseguir la síntesis de receptores cuyo comportamiento como sensores moleculares puedan ser evaluados a través de varios canales, como puede ser la detección visual, o a través de técnicas espectroscópicas y electroquímicas. Otra forma de lograr el reconocimiento de analitos implica el uso de reacciones químicas irreversibles, inducidas por un analito específico, sobre la molécula del receptor, dando lugar a una señal medible en tiempo real. Debido a que tales reacciones irreversibles dan lugar a productos químicamente diferentes a la molécula de receptor de partida, este proceso de reconocimiento es conocido como el “método del quimiodosímetro”. Por lo tanto, mientras que la forma de operar de un sensor químico se basa en procesos de coordinación reversibles, la de un quimiodosímetro se basa en una reacción irreversible entre receptor y analito. En consecuencia, otro de los objetivos planteados en esta Tesis consiste en el diseño y estudio de una serie de quimiodosímetros para el reconocimiento de aniones. En primer lugar, hemos preparado un receptor heteroditópico en el que una unidad de ferroceno está unido a un imidazo[4,5-e]-2,1,3-benzotiadiazol. La característica estructural más importante de este sistema es la presencia de un anillo de tiadiazol fusionado de forma angular a una unidad de benzimidazol, de manera que los átomos de nitrógeno que se encuentran en la cavidad generada por este sistema heterocíclico pudiesen cooperar sinérgicamente en el reconocimiento de especies catiónicas, mientras que el grupo NH del anillo de imidazol quedaría disponible para el reconocimiento, por puentes de hidrógeno, de especies aniónicas. De hecho, este receptor se comporta como un sensor electroquímico y cromogénico altamente selectivo para cationes Pb2+. Además, los estudios electroquímicos llevados a cabo sobre el comportamiento de este receptor frente a aniones HP2O73- mostraron un reconocimiento selectivo de este anión. En el segundo capítulo, hemos diseñado y preparado una familia de sensores químicos con estructura del tipo 2-arilamino-1,3-diaza[3]ferrocenofano, en los que se combina la actividad redox de la unidad de ferroceno y el carácter cromogénico de los grupos azo arilo y p-nitrofenilo con la capacidad de la unidad de guanidina para actuar como centro de reconocimiento. Debido a la naturaleza anfótera de la unidad de guanidina, también se ha evaluado su capacidad en su forma monoprotonada para actuar como unidad de reconocimiento frente a aniones. El primer receptor estudiado, portador de un grupo p-nitrofenilo, permite la detección de aniones AcO-, PhCO2-, F-, Cl- y Br- mediante el uso de técnicas electroquímicas y espectroscópicas (1H-RMN y UV-Vis). Su forma monoprotonada es capaz de detectar selectivamente los aniones menos básicos Cl-, Br- y NO3- a través de los mismos canales ya citados anteriormente. El receptor que contiene un derivado azo unido al resto de guanidina, muestra una alta afinidad por el anión acetato en acetonitrilo a través de un doble canal: electroquímico y cromogénico. En su forma monoprotonada es capaz de detectar selectivamente los aniones menos básicos Cl-, Br-, NO3- y HSO4- a través de medidas electroquímicas y espectroscópicas (1H-RMN y UV-Vis). En el tercer capítulo, se describe la síntesis y estudio como quimiosensores de una serie de compuestos del tipo [m.m] ferrocenofanos portadores de puentes aldimínicos, que pueden actuar como centros de reconocimiento de cationes, y un espaciador aromático o heteroaromático (tiofeno), y también de una familia de ferroceniliminas con estructura acíclica. La incorporación de grupos con propiedades fluorescentes a los receptores de naturaleza acíclica permite el estudio de estos receptores a través de un tercer canal: fluorescencia. Los anillos de quinoleina o pireno y el grupo difenilfosforilo son las unidades que se encuentran directamente unidos a la agrupación imina en los receptores de cadena abierta. Los dos receptores [m.m]ferrocenofánicos actúan como quimiosensores cromogénicos eficientes de cationes Zn2+, Pb2+ y Hg2+ en CH3CN. Los cambios en los espectros de absorción están acompañados por un cambio de color que permite la detección de estos cationes a simple vista. Los cálculos a nivel DFT revelan una inusual coordinación cúbica distorsionada para el catión Pb2+ en el complejo formado con el receptor que contiene las unidades de tiofeno, ubicado en una jaula tipo dador N4S4. El receptor que contiene el anillo de quinoleina se comporta como sensor químico para los cationes Ni2+, Zn2+, Cd2+, Hg2+ y Pb2+ a través de dos canales diferentes: electroquímico y cromogénico. Sin embargo, el receptor que contiene el anillo de pireno, se comporta como sensor químico óptico y electroquímico para los cationes Zn2+, Hg2+ y Pb2+en CHCl3. No obstante, al utilizar la mezcla CHCl3/DMF (9: 1) como disolvente, este receptor se comporta como un quimiodosímetro fluorescente que detecta selectivamente la presencia de Hg2+, incluso en presencia de un gran exceso del resto de cationes metálicos testados. Finalmente, los estudios electroquímicos y espectroscópicos llevados a cabo con el receptor que contiene el resto de óxido de fosfina mostraron la afinidad de este receptor hacia los cationes metálicos Li+, Ca2+, Mg2+, Zn2+ y Pb2+. A través de los datos de valoración por 1H-RMN y cálculos DFT se han propuesto modos de enlace para estos complejos metálicos. Por último, en el capítulo cuatro, hemos diseñado y preparado dos quimiodosímetros para el reconocimiento de aniones. El primero de ellos es una díada ferroceno-pirilio que se comporta como un quimiodosímetro selectivo para los aniones tóxicos cianuro y sulfuro de hidrógeno. Una característica destacada de este receptor, es la presencia de un anillo de pirilio capaz de reaccionar con estas especies aniónicas en agua para dar productos acíclicos, que presentan un cambio fácilmente detectable en el potencial redox de la pareja ferroceno/ferrocinio y una notable perturbación en el espectro de absorción, que puede ser utilizada para la detección a simple vista de estos aniones. El otro receptor, presenta una estructura tipo [11]ferrocenofano y contiene dos unidades de urea. La característica principal de este receptor es que el átomo de hierro del ferroceno se encuentra en estado de oxidación Fe3+. Este receptor se comporta como un quimiodosímetro electroquímico y óptico selectivo para aniones NO2-. Los cambios observados corresponden a una reacción de nitración del grupo urea presente en el receptor y no a la reducción Fe3+ → Fe2+ del átomo de hierro presente en el receptor. / One of the challenges been actually facing by the chemistry is related to the development of methods for the effective, sensitive, selective and real-time detection of substances which are responsible for the environmental pollution or are involved in biological and clinical processes. It is therefore not surprising that over the last decades, the development of chemical sensors for this type of species is one of the most active research fields. In this context, the main objectives of this PhD thesis are aimed to the design, synthesis and study of structurally simple molecules capable of behaving as molecular sensors for analytes such as anions and cations. To this end, the synthesized receptors should contain two basic parts: a recognition unit and a signal transduction unit which allows the detection of the coordination or binding event through the changes taking place in the properties of the receptor (electrochemical, colorimetric or fluorescent) as the recognition process progresses. Despite the development of classical optical or electrochemical chemosensors for cation and anion sensing, there is a paucity of use of multichannel signaling anion chemosensor molecules. Thus, we focused the work contained in this PhD thesis in getting the challenge of synthesizing receptors whose sensing behavior can be evaluated via multichannel ways such as visual detection, electronic and 1H NMR spectral and electrochemical techniques. Another way to achieve analyte recognition involves the use of irreversible reactions induced by a specific analyte on the receptor molecule, yielding measurable signals with a real-time response. Because such irreversible reactions result in products chemically different from the starting receptor molecule, this approach is known as the chemodosimeter approach. Thus, while the chemosensor approach is based on typical reversible coordination events, the chemodosimeter protocol is based on irreversible reactions between the receptor and the analyte. Consequently, another objective of this Thesis is related to the design and study of a series of chemodosimeters for the recognition of anionic analytes. In a first step we have prepared a ferrocene-based heteroditopic receptor in which the ferrocene moiety is attached to an imidazo[4,5-e]-2,1,3-benzothiadiazole. The most significant structural feature of this system is the presence of a thiadiazole ring angularly fused to a benzimidazole unit, so that the nitrogen atoms placed in the cavity created by the heterocyclic system could cooperate synergistically in recognizing cationic species, while the NH group of the imidazole ring would be available for recognition of anionic species thorough hydrogen bonding. In fact, this receptor behaves as a highly selective dual-redox and chromogenic chemosensor molecule for Pb2+ cations. Moreover, electrochemical studies on the behaviour of this receptor towards anions showed a selective recognition of HP2O73- anions. In the second chapter, we have designed and prepared a family of chemosensors with a structure 2-arylamino-1,3-diaza[3]ferrocenophanic, in which we combine the redox activity of the ferrocene unit with the chromogenic behavior of the aryl azo y p-nitrophenyl functionality and the binding ability of the guanidine group. Due to the amphoteric nature of the guanidine unit, has also been studied for binding ability its monoprotonated form. The first receptor we have designed, which contains a p-nitrophenyl group, allows the sensing of AcO-, PhCO2-, F-, Cl- and Br- anions through a electrochemical and spectroscopic (1H-NMR and UV-Vis) measurements. Its monoprotonated form is able to selectively sense the less basic Cl-, Br-, NO3- anions through a electrochemical and spectroscopic (1H-NMR and UV-Vis) measurements. The guanidine derivative receptor, which contains an azo derivative, exhibits high binding affinity and sensitivity for the Y-shaped acetate anion in acetonitrile through a dual channel, electrochemical and chromogenic Its monoprotonated form is able to selectively sense the less basic Cl-, Br-, NO3-, and HSO4- anions through a electrochemical and spectroscopic (1H-NMR and UV-Vis) measurements. In the third chapter, we describe the synthesis and electrochemical, optical, and ion sensing properties of [m.m]ferrocenophanes with bridges decorated with aldimine as cation-binding site and an aromatic or heteroaromatic (thiophene) spacer, and also a family of ferrocenilimines with acyclic structure. The incorporation of fluorescent properties groups some of the receptors acyclic nature allows the study of these receptors via a third channel: fluorescence. Quinoline, pyrene and diphenylphosphoryl units are directly attached to the unit guanidine these receptors. Both receptors [m.m]ferrocenophanes act as efficient redox/chromogenic chemosensor molecules for Zn2+, Pb2+, and Hg2+ cations in CH3CN. The changes in the absorption spectra are accompanied by a color change which allows the potential for “naked eye” detection. DFT calculations reveal an unusual distorted cubic coordination for the Pb2+ cation in the complex formed with the receptor bearing thiophene units in a N4S4 donor cage. The receptor bearing a quinoline ring behaves as chemosensor molecule for Ni2+, Zn2+, Cd2+, Hg2+ and Pb2+. cations acting through two different channels: electrochemical and chromogenic. Whereas, receptor bearing a pyrene ring, behaves as a dual redox and optical chemosensor molecule for Zn2+, Hg2+ and Pb2+ metal cations in CHCl3. However, by using CHCl3/DMF (9:1) as solvent this receptor behaves as a fluorometric chemodosimeter which selectively senses the presence of Hg2+ even in the presence of a large excess of the other metal cations tested. Finally, electrochemical and spectroscopies studies carried out on the receptor bearing phosphine oxide moiety showed the affinity of this receptor to metal cations such as Li+, Ca2+, Mg2+, Zn2+ and Pb2+ metal cations. The 1H-NMR titration data and DFT calculations plausible binding modes receptors-metals have also been proposed. Finally, in the chapter four, we have designed and prepared two chemodosimeters for the recognition of anionic analytes. The first is a ferrocene-pyrylium dyad behaves as a selective chemodosimeter for the toxic cyanide and hydrogensulfide anions. A salient feature of this simple receptor, is the presence of a reactive pyrylium ring able to react with these anionic species in water to give acyclic products, exhibiting an easily detectable signal change in the redox potential of the ferrocene/ferrocinium redox couple and a remarkable perturbation in the absorption spectrum, which can be used for “naked eye” detection of these anions. The other receptor, presents a [11]ferrocenophane structure bearing two urea units. The main feature of this receptor is that the iron atom of ferrocene is in Fe3+ oxidation state. This receptor behaves as a selective dual-redox and chromogenic chemodosimeter for NO2- anions. The observed changes correspond to a nitration reaction of the urea group present in the receptor but not to a reduction of the Fe3+ atom (Fe3+→Fe2+) present within the receptor.
|
525 |
Desarrollo de la estrategia analítica multiconmutación-fotodegradación-luminiscencia para la automatización en el control de pesticidas. Aplicación de la conectividad molecular para la predicción de los procesos estructurales.Albert García, Jose Ramón 31 October 2008 (has links)
A high-priority line research in Analytical Chemistry is the development of methods and techniques that increase the automatization degree and, therefore, reduce the human participation in the analysis procedures. The demand of information makes necessary the development of simple, cheap, fast and clean methodologies. This Doctoral Thesis was devoted to develop new and automated systems for pesticide analysis on samples of environmental interest. To achive this goal we studied an analytical strategy based on Multicommutation, luminescence (chemiluminescence and fluorescence) and photodegradation. To implement the analytical objectives we also applied the Molecular Connectivity to predict the luminescent behaviour of organic molecules. This Doctoral Thesis combines a new, cost-effective and sensitive analytical strategy for the determination of pesticides based on:- Multicommutation, an automatic methodology by using solenoid valves device,- Luminescence as high sensitive detection technique and,- Photodegradation as a simple derivative mean of analytes, And a way to predict the luminescent properties of organic molecules by using the Molecular Connectivity. All together would be useful in the future help in the search and selection of new structures with theoretical luminescent or others interesting properties.
|
526 |
Diferents estratègies per augmentar la sensibilitat en eleccroforesi capil·lar. Aplicació a la determinació de fàrmacs antiinflamatorisMacià i Puig, Ma Alba 21 December 2006 (has links)
La Tesi Doctoral que porta per títol, "Diferents estratègies per augmentar la sensibilitat en electroforesi capil·lar. Aplicació a la determinació de fàrmacs antiinflamatoris", s'ha basat en el desenvolupament de diferents estratègies per a disminuir els límits de detecció (LODs) de l'electroforesi capil·lar (CE) a la determinació de fàrmacs antiinflamatoris. Les estratègies desenvolupades s'han basat en la injecció d'un gran volum de mostra en el capil·lar mitjançant l'aplicació de tècniques de preconcentració tant electroforètiques com cromatogràfiques, i en l'ús de l'espectrometria de masses (MS) com a sistema de detecció per augmentar la capacitat de detecció dels analits. La present Tesi Doctoral s'ha centrat en la determinació de fàrmacs antiinflamatoris no esteroïdals (NSAIDs) en el medi ambient aquàtic a baixos nivells de concentració. L'interès a la determinació d'aquests ha augmentat molt darrerament degut al seu elevat consum tant en espècies humanes com en animals. Aquests fàrmacs arriben a les estacions de tractament d'aigües residuals (EDAR) a través de diferents procedències, i posteriorment aquests poden entrar en el medi ambient aquàtic degut a la seva gran estabilitat. Diferents estudis han demostrat la determinació d'aquests fàrmacs a nivells de baixos ng·L-1 en les aigües superficials. Aquests estudis s'han realitzat principalment tant per cromatografia de gasos (GC) com per cromatografia de líquids (HPLC) emprant l'MS com a sistema de detecció. L'CE també ha estat emprada per la determinació d'aquests fàrmacs, però la seva aplicació principal ha estat en l'anàlisi de mostres biològiques. Tot i els grans avantatges que proporciona la tècnica d'CE, aquesta presenta una baixa sensibilitat que limita la determinació d'analits a baixos nivells de concentració. Aquest fet és degut com a conseqüència del petit volum de mostra que es pot injectar en el capil·lar i del petit camí òptic que tenen els capil·lars que sutilitzen. Amb l'objectiu de millorar la sensibilitat de la tècnica i d'ampliar la seva aplicabilitat en altres camps, com el mediambiental, el desenvolupament de diferents estratègies per a disminuir els LODs són molt importants i són objecte d'estudi de diferents grups d'investigació. En la present Tesi Doctoral s'han aplicat i comparat diferents tècniques de preconcentració electroforètiques per la determinació d'aquests fàrmacs en els diferents modes electroforètics, com l'electroforesi capil·lar per zones (CZE), la cromatografia capil·lar de microemulsió electrocinètica (MEEKC) i la cromatografia capil·lar micel·lar electrocinètica (MEKC). La majoria d'aquestes tècniques s'han basat en la supressió del flux electroosmòtic (EOF) per eliminar la matriu de la mostra del capil·lar desprès d'haver injectat un gran volum de mostra. L'avantatge d'addicionar un supressor de l'EOF al medi electrolític és que aplicant un sol voltatge negatiu es duu consecutivament la preconcentració i la separació electroforètica. L'aplicació d'una tècnica de preconcentració cromatogràfica, basada en l'acoblament in-line entre l'extracció en fase sòlida (SPE) i l'CE, també s'ha aplicat a la determinació de NSAIDs en una mostra d'aigua. El gran potencial de les tècniques de preconcentració tant electroforètiques com cromatogràfiques és que ha permès la determinació d'aquests fàrmacs a nivells de ng·L-1. Aquests resultats s'han obtingut emprant prèviament la tècnica d'SPE off-line per preconcentrar els analits i netejar la matriu de la mostra. Una altra estratègia emprada per la determinació de NSAIDs en el medi ambient aquàtic ha estat l'ús de l'MS com a sistema de detecció. Aquest acoblament permet la confirmació i la identificació dels diferents analits que puguin estar presents en una mostra. D'aquesta manera, ha estat possible la determinació dels fàrmacs en estudi en aigües superficials i la identificació d'aquests en les aigües procedents de diferents estacions EDAR. En aquest cas s'han emprat com a tècniques de pretractament la tècnica d'SPE off-line, i la combinació de l'extracció líquid-líquid (LLE) i l'SPE off-line, respectivament. / The entitled Doctoral Thesis, "Diferents estratègies per augmentar la sensibilitat en electroforesi capil·lar. Aplicació a la determinació de fàrmacs antiinflamatoris", has been based on the development of different strategies to decrease the limits of detection (LODs) in capillary electrophoresis (CE) to determine anti-inflammatory drugs. The developed strategies have been based on injecting a large volume of sample into the capillary by application electrophoretic and chromatographic preconcentration techniques, and using the mass spectrometry (MS) as the detection system to increase the detection capacity of the analytes. This Doctoral Thesis has been centred on the determination of nonsteroidal anti-inflammatory drugs (NSAIDs) in the aquatic environment at low concentration levels. In the last years, the interest to determine them has considerably grown due to the high consume in humans and in animals. These drugs arrive in the sewage treatment plants (STPs) by different source, and subsequently these can entry into the aquatic environment due to its high stability. Different studies have demonstrated the determination of these drugs at low ng·L-1 levels in surface waters. These studies have principally carried out by gas chromatography (GC) and liquid chromatography (HPLC) by using mass spectrometry as the detection system. CE has also been used to determine these drugs, but its principal application has been for the analysis of biological samples. Although the high advantages that presents the technique, this shows a low sensitivity that overcomes the determination of analytes at low concentration levels. This is a consequence of the low amount of sample that can be injected into the capillary and the small path length. With the aim of improving the sensitivity and extending the CE applicability in others fields, such as the environmental, then the development of different strategies to decrease the LODs are very important and these are object of studying of different research groups. In this Doctoral Thesis have been applied and compared different electrophoretic preconcentration techniques to determine these drugs in the different electrophoretic modes, such as capillary zones electrophoresis (CZE), microemulsion electrokinetic capillary chromatography (MEEKC) and micellar electrokinetic capillary chromatography (MEKC). Frequently, in these preconcentration techniques the sample matrix has been removed from the capillary by suppressing the electroosmotic flow (EOF). The advantage of adding an EOF suppressor in the electrophoretic medium is that the preconcentration and the electrophoretic separation can consecutively be performed by applying an only negative voltage. The application of a chromatographic preconcentration technique, based on the in-line coupling between solid phase extraction (SPE) and CE, has also been applied to determine NSAIDs in water samples. The high potential of the electrophoretic and the chromatographic preconcentracion techniques, is that allow to determine these drugs at ng·L-1 levels. These results have been obtained by using the technique off-line SPE to preconcentrate the analytes and to clean-up the sample matrix before the application of the preconcentration technique. Other strategy used to determine NSAIDs in the aquatic environment at low levels has been the use of MS as the detection system. This coupling allows confirming and identifying the presence of the analytes in the sample. So, it has been possible the determination of the studied drugs in surface waters and their identification in the STPs. In this study, the technique off-line SPE and the combination of liquid-liquid extraction (LLE) and off-line SPE off-line, respectively, have been used as the sample pretreatment technique.
|
527 |
La cromatografía líquida micelar: una técnica competitiva frente a la cromatografía líquida en fase inversa clásicaRuiz Ángel, Maria Jose 04 July 2003 (has links)
Se presenta una serie de estudios en los que se compara el uso de sistemas cromatográficos de fase inversa micelares y acuo-orgánicos clásicos, para el análisis de varias familias de compuestos de interés en la industria farmacéutica (antidepresivos tricíclicos, ?-bloqueantes, diuréticos, esteroides y sulfonamidas), cuya elución cuando se emplean fases móviles acuo-orgánicas y fases estacionarias alquil-enlazadas convencionales, puede originar serios inconvenientes. Se muestran también tres aplicaciones de la cromatografía líquida micelar (CLM) al control de fármacos en preparados farmacéuticos y muestras de orina. Las investigaciones realizadas se agrupan de la siguiente manera: (i) comparación de las capacidades separativas de los sistemas cromatográficos micelares y acuo orgánicos clásicos y(ii) desarrollo de nuevos procedimientos para la determinación de fármacos. Las investigaciones de tipo fundamental abordan aspectos relacionados con las eficacias y simetrías de los picos cromatográficos, la fuerza eluyente, la resolución, la capacidad de "screening" de la CLM y la optimización de las condiciones de separación, considerando tanto la composición de la fase móvil como el pH. Se establecen unos principios básicos de selección del disolvente orgánico en las fases micelares, basados en la correlación existente entre la retención y la polaridad de los compuestos separados. Se utilizan las mismas herramientas quimiométricas para realizar las comparaciones entre los dos sistemas de fase inversa, micelar y acuo-orgánico. En la bibliografía, no existe antecedente sobre estudios similares. El examen detallado del comportamiento cromatográfico de los compuestos de prueba que poseen una gran diversidad de estructuras, polaridades y comportamiento ácido-base, demuestra que la CLM es una técnica muy competitiva frente a la cromatografía de fase inversa clásica. Como aspectos relevantes presenta su menor toxicidad debido a la importante reducción de disolvente orgánico, sus características de retención que evitan la elución en gradiente, su particular selectividad, distinta de la cromatografía clásica, su versatilidad, la posibilidad de eluir compuestos muy apolares con ayuda de disolventes que se solubilizan gracias a la presencia de las micelas y la mejora espectacular de la forma de los picos de los compuestos básicos. Estas características permiten el uso de columnas convencionales de bajo precio y la posibilidad de inyectar directamente muestras con un elevado contenido en proteínas, como son las muestras fisiológicas. Finalmente, los estudios aplicados se refieren al desarrollo de procedimientos para la determinación de antidepresivos tricíclicos en preparados farmacéuticos empleando fases móviles micelares y acuo orgánicas, que incluye una comparación de varias fases estacionarias, y la determinación del ? bloqueante propranolol a través del control de sus metabolitos y del diurético furosemida junto con sus productos de degradación, en muestras de orina y empleando la CLM. / In this work, micellar and classical aqueous-organic chromatographic systems are compared in order to analyse several groups of interest in the pharmaceutical industry (tricyclic antidepressants, ?-blockers, diuretics, steroids and sulfonamides), which give rise to serious problems when eluting with aqueous-organic mobile phases and using conventional alkyl-bonded stationary phases. Micellar liquid chromatography (MLC) is also applied to the control of therapeutic active principles contained in pharmaceuticals and urine samples.The research work is divided as follows:(i) comparison of the chromatographic separation obtained with micellar and aqueous-organic systems and(ii) developing of new procedures to the control of pharmaceutical products. Fundamental studies consider aspects related to efficiencies and assymetries of the chromatographic peaks, elution strength, resolution, screening capability using MLC and optimisation of the separation conditions considering mobile phase composition and pH. Some basic principles to select the organic solvent in micellar mobile phases are established. These are based on the correlation existing between retention and polarity of the compounds to separate.The same chemometric tools are used to perform the comparison between the two reversed-phase systems, micellar and aqueous-organic modes. In the literature, it is not possible to find similar studies. A detailed examination of the chromatographic behaviour of the test compounds, showing a great diversity of structures, polarities and acid-base behaviour, revealed that MLC is a very competitive technique versus classical reversed-phase liquid chromatography. Some relevant aspects of micellar systems are: their low toxicity, due to the low amount of organic solvent used, the characteristics of retention, which avoid the use of a gradient mode, their particular selectivity, versatility, the possibility of eluting very low polar compounds, and a great improvement of the shape of the chromatographic peaks showed by basic compounds. This permits the use of low price conventional columns and the possibility of direct injection of samples with a high content of proteins. Finally, the applied studies show three procedures to determine tricyclic antidepressants in pharmaceuticals using micellar and hydro-organic mobile phases, including the comparison of several stationary phases, and the control of the ?-blocker propranolol through its metabolites and the diuretic furosemide joint to its degradation products, in urine samples using MLC.
|
528 |
New Instrumental and Chemometric Developments form the on-line hyphenation of Liquid Chromatography and Infrared SpectroscopyKuligowski, Julia 14 December 2011 (has links)
The coupling of liquid chromatography (LC) to infrared (IR) spectrometry is an interesting analytical tool, because high resolution provided by LC is combined with the non-destructive and molecular specific information of IR spectrometry. However, the potential of on-line LC-IR employing a flow cell interface, characterized by its technical simplicity, cannot yet be fully exploited due to the limited sensitivity of IR detection and difficulties in on-line measurements arising from the dominating absorption of most of the commonly used mobile phase components. Accordingly, the objective of this Thesis was to promote the use of the on-line hyphenation of LC and IR spectroscopy through the development of instrumental and chemometric tools to overcome existing limitations, thus increasing the applicability of this technique.
Chapter 2 describes innovations in the field of isocratic separation. A method for the determination of lecithin and soybean oil in dietary supplements using on-line Gel Permeation Chromatography – Attenuated Total Reflectance – Infrared (GPC-ATR-IR) was developed including a simple procedure to select the optimum wavenumber used for the extraction of characteristic elution profiles. For the monitoring of polymerized triglycerides in deep-frying oil, an approach employing on-line GPC-IR spectrometry and the Science Based Calibration (SBC) multivariate approach for chromatogram-extraction were reported. An on-line LC-IR procedure for the determination of glycolic acid in cosmetics employing the rapid scan data acquisition mode was proposed.
Chapter 3 deals with different methods for background correction in on-line LC-IR using reference spectra matrices (RSM). The determination of the critical eluent composition for polyethylene glycols using methanol as organic modifier was discussed employing the absorbance ratio as identification parameter for background correction. For the determination of fructose, glucose, sucrose and maltose in beverages employing acetonitrile as organic modifier, again the absorbance ratio was used as identification parameter. A Partial Least Squares (PLS) procedure as well as the application of point-to-point matching algorithms for automated background correction were discussed for background correction in acetonitrile:water gradients using different examples of applications.
Chapter 4 deals with the compensation of the background contribution employing column-wise techniques. Polynomial regressions modelling the background absorbance at each wavenumber throughout the gradient run were applied for acetonitrile:water mobile phase
gradients. The use of cubic smoothing splines could be demonstrated for background correction under reversed phase gradient conditions employing different alcohols as organic modifiers.
In Chapter 5, background correction based on factor analysis and reference spectra matrices was discussed. The contribution of the background absorption to overall LC-IR signals could be compensated using two approaches based on Principal Component Analysis (PCA) and simple-to-use interactive self modeling analysis (SIMPLISMA), obtaining good results in acetonitrile:water systems. Subsequently, multivariate curve resolution-alternating least squares (MCR-ALS) was applied improving peak and spectral resolution and eliminating remaining signal variation due to background absorption and detector drift.
The chemometric extraction of ‘analyte-specific’ chromatograms in on-line LC-IR was discussed in Chapter 6. Obtained results confirm that the SBC method is particularly well suited for recovering ‘analyte-specific’ signals from on-line LC-IR chromatograms.
The last chapter describes instrumental developments in on-line LC-IR. On-line IR detection in gradient capillary LC using micromachined nanoliter-flow cells was discussed. Four model compounds were separated and identified using an acetonitrile:H2O gradient with limits of detection in the concentration range of 35-94 ng μL-1, representing an increase in mass sensitivity by a factor of approximately 30 as compared to standard LC systems. The last chapter also focuses on the development of LC with on-line dual Quantum Cascade Laser (QC-laser) detection. Compared to state-of-the-art FTIR spectrometers, the use of the developed QC-laser based system provided a significant improvement in both, sensitivity and data acquisition frequency. / The coupling of liquid chromatography (LC) to infrared (IR) spectrometry is an interesting analytical tool, because high resolution provided by LC is combined with the non-destructive and molecular specific information of IR spectrometry. However, the potential of on-line LC-IR employing a flow cell interface, characterized by its technical simplicity, cannot yet be fully exploited due to the limited sensitivity of IR detection and difficulties in on-line measurements arising from the dominating absorption of most of the commonly used mobile phase components. Accordingly, the objective of this Thesis was to promote the use of the on-line hyphenation of LC and IR spectroscopy through the development of instrumental and chemometric tools to overcome existing limitations, thus increasing the applicability of this technique.
Chapter 2 describes innovations in the field of isocratic separation. A method for the determination of lecithin and soybean oil in dietary supplements using on-line Gel Permeation Chromatography – Attenuated Total Reflectance – Infrared (GPC-ATR-IR) was developed including a simple procedure to select the optimum wavenumber used for the extraction of characteristic elution profiles. For the monitoring of polymerized triglycerides in deep-frying oil, an approach employing on-line GPC-IR spectrometry and the Science Based Calibration (SBC) multivariate approach for chromatogram-extraction were reported. An on-line LC-IR procedure for the determination of glycolic acid in cosmetics employing the rapid scan data acquisition mode was proposed.
Chapter 3 deals with different methods for background correction in on-line LC-IR using reference spectra matrices (RSM). The determination of the critical eluent composition for polyethylene glycols using methanol as organic modifier was discussed employing the absorbance ratio as identification parameter for background correction. For the determination of fructose, glucose, sucrose and maltose in beverages employing acetonitrile as organic modifier, again the absorbance ratio was used as identification parameter. A Partial Least Squares (PLS) procedure as well as the application of point-to-point matching algorithms for automated background correction were discussed for background correction in acetonitrile:water gradients using different examples of applications.
Chapter 4 deals with the compensation of the background contribution employing column-wise techniques. Polynomial regressions modelling the background absorbance at each wavenumber throughout the gradient run were applied for acetonitrile:water mobile phase
J. Kuligowski | NEW INSTRUMENTAL AND CHEMOMETRIC DEVELOPMENTS FOR THE ON-LINE HYPHENATION OF
LIQUID CHROMATOGRAPHY AND INFRARED SPECTROSCOPY
II
gradients. The use of cubic smoothing splines could be demonstrated for background correction under reversed phase gradient conditions employing different alcohols as organic modifiers.
In Chapter 5, background correction based on factor analysis and reference spectra matrices was discussed. The contribution of the background absorption to overall LC-IR signals could be compensated using two approaches based on Principal Component Analysis (PCA) and simple-to-use interactive self modeling analysis (SIMPLISMA), obtaining good results in acetonitrile:water systems. Subsequently, multivariate curve resolution-alternating least squares (MCR-ALS) was applied improving peak and spectral resolution and eliminating remaining signal variation due to background absorption and detector drift.
The chemometric extraction of ‘analyte-specific’ chromatograms in on-line LC-IR was discussed in Chapter 6. Obtained results confirm that the SBC method is particularly well suited for recovering ‘analyte-specific’ signals from on-line LC-IR chromatograms.
The last chapter describes instrumental developments in on-line LC-IR. On-line IR detection in gradient capillary LC using micromachined nanoliter-flow cells was discussed. Four model compounds were separated and identified using an acetonitrile:H2O gradient with limits of detection in the concentration range of 35-94 ng μL-1, representing an increase in mass sensitivity by a factor of approximately 30 as compared to standard LC systems. The last chapter also focuses on the development of LC with on-line dual Quantum Cascade Laser (QC-laser) detection. Compared to state-of-the-art FTIR spectrometers, the use of the developed QC-laser based system provided a significant improvement in both, sensitivity and data acquisition frequency.
|
529 |
Tandem time-of-flight mass spectrometry incorporating quadratic-field technologyThomas, Benjamin January 2000 (has links)
The study involved the desig~ constructio~ optimisation and utilisation of a novel tandem time-of-flight (TOF-TOF) instrument. The instrument was designed to use a laser ion source capable of laser desorption or matrix-assisted laser desorption/ionisation. The instrument used a twin ion mirror geometry in which the first ion mirror was a single-stage ion mirror, while the second ion mirror was a quadratic-field ion mirror. The instrument was designed for highenergy (>10keV) collision-induced dissociation (CID). The initial design criteria of a tandem time-of-flight spectrometer are discussed. The design and construction of the vacuum chamber and pumping system are discussed. The design and construction of the laser ion source are covered in detail. Computer simulations of typical ion trajectories were calculated using the SIMION program. The design and construction of the steering optics, single-stage ion mirror and pulsed mass gate are discussed. Computer simulations of ion trajectories were used to characterise the ion optical properties of the system. Experiments to characterise the energy focusing properties and transmission of the single-stage ion mirror were conducted. The mass resolving power of the single-stage ion mirror were characterised. The single-stage ion mirror achieved a resolution of2000 full-width half-maximum (FWHM). The design and construction of the differentially pumped collision-cell and the quadratic-field ion mirror are outlined. Experiments to demonstrate the transmission of the collision-cell and quadratic-field ion mirror are discussed. Experiments to characterise the energy focusing properties of the quadratic-field ion mirror were conducted. The full instrument achieved precursor mass resolving powers of approximately 7000 (FWHM) for laser desorbed species and 3500 (FWHM) for MALDI generated peptide species. Initial CID results are presented. The study thoroughly discusses the problems with the current instrument configuration and goes on to propose solutions to the problems encountered.
|
530 |
Diseño de test de cualificación OQ y PQ en HPLC y desarrollo de modelos de cálculo de la incertidumbre a partir de la validación de procedimientos de análisisQuintela Bermejo, Juan Manuel 16 July 2015 (has links)
A la present tesi s'han desenvolupat i aplicat metodologies per reforçar les bases de la qualitat en els laboratoris d'anàlisi, és a dir, orientades a proporcionar dades fiables i vàlides per a l'ús previst. Aquestes activitats s'han dut a terme considerant els requeriments dels sistemes de qualitat ISO 9001, ISO 17025, BPL i GMP.
En el primer bloc, s'han desenvolupat eines útils en la qualificació d'equips:
- El test OQ (Qualificació Operacional) permet assegurar des d'un punt de vista modular el bon funcionament d'un cromatògraf de líquids. S'han utilitzat els resultats històrics de confirmació metrològica de l'equip per establir els criteris d'acceptació corresponents.
- El test PQ (Qualificació d'Execució de Procés) es basa en l'anàlisi d'una barreja de quatre substàncies. L'avaluació dels paràmetres establerts permet comprovar el correcte funcionament del cromatògraf de líquids des d'un punt de vista global o de "caixa negra" i, fins i tot, identificar quin mòdul de l'equip no està funcionant correctament.
En el segon bloc, s'ha estudiat la validació de procediments d'anàlisi i la seva aplicació en el càlcul de la incertesa associada a les mesures.
- S'ha optimitzat i revalidat el procediment d'anàlisi de nitrogen Kjeldahl en mostres de taurina. Les condicions de treball s'han modificat, tenint en compte els resultats disponibles de la confirmació metrològica de l'equip.
- S'ha desenvolupat una metodologia per al càlcul de la incertesa aprofitant els resultats que s'obtenen durant la validació dels procediments d'anàlisi. Aquesta metodologia s'ha aplicat en la determinació de clorurs en lixiviats per HPLC i en la determinació de la distribució d'àcids grassos en mostres de estearat de magnesi per GC. / En la presente tesis se han desarrollado y aplicado metodologías para reforzar las bases de la calidad en los laboratorios de análisis, es decir, orientadas a proporcionar datos fiables y válidos para el uso previsto. Estas actividades se han llevado a cabo considerando los requerimientos de los sistemas de calidad ISO 9001, ISO17025, BPL y GMP.
En el primer bloque, se han desarrollado herramientas útiles en la cualificación de equipos:
- El test OQ (Cualificación Operacional) permite asegurar desde un punto de vista modular el buen funcionamiento de un cromatógrafo de líquidos. Se han utilizado los resultados históricos de confirmación metrológica del equipo para establecer los criterios de aceptación correspondientes.
- El test PQ (Cualificación de Ejecución de Proceso) se basa en el análisis de una mezcla de cuatro sustancias. La evaluación de los parámetros establecidos permite comprobar el correcto funcionamiento del cromatógrafo de líquidos desde un punto de vista global o de “caja negra” e, incluso, identificar qué módulo del equipo no está funcionando correctamente.
En el segundo bloque, se ha estudiado la validación de procedimientos de análisis y su aplicación en el cálculo de la incertidumbre asociada a las medidas.
- Se ha optimizado y revalidado el procedimiento de análisis de nitrógeno Kjeldahl en muestras de taurina. Las condiciones de trabajo se han modificado, teniendo en cuenta los resultados disponibles de la confirmación metrológica del equipo.
- Se ha desarrollado una metodología para el cálculo de la incertidumbre aprovechando los resultados que se obtienen durante la validación de los procedimientos de análisis. Esta metodología se ha aplicado en la determinación de cloruros en lixiviados por HPLC y en la determinación de la distribución de ácidos grasos en muestras de estearato de magnesio por GC. / In this thesis, there have developed and applied methodologies to strengthen the foundations of quality in laboratories, that is, aimed at providing reliable and valid for the intended use. These activities have been carried out considering the requirements of the following quality systems: ISO 9001, ISO 17025, GLP and GMP.
In the first block, there have developed useful tools in the qualification of equipment:
- OQ test (Operational Qualification) ensures from a modular point of view the proper functioning of a liquid chromatograph. There have used historical results of metrological confirmation of the equipment to set appropriate acceptance criteria.
- PQ test (Qualification Process Execution) is based on the analysis of a mixture of four substances. Evaluation of established parameters allows to check proper operation of the liquid chromatograph from a global or "black box" perspective, and even, identify which equipment module is not working properly.
In the second block, there have studied the validation of analytical procedures and their application in the calculation of the uncertainty associated with the measures.
- It was optimized and revalidated the procedure for Kjeldahl nitrogen analysis in taurine samples. Working conditions have changed, taking into account the available results of the metrological confirmation of equipment.
- It has developed a methodology to calculate the uncertainty using the results obtained during validation of analytical procedures. This methodology has been applied in the determination of chloride in the leaching by HPLC and in the determination of fatty acids in samples of magnesium stearate by GC.
|
Page generated in 0.032 seconds