{"id":114994,"date":"2018-03-11T10:43:16","date_gmt":"2018-03-11T10:43:16","guid":{"rendered":""},"modified":"2018-03-11T10:43:16","modified_gmt":"2018-03-11T10:43:16","slug":"hifenaciones-instrumentales-entre-la-cromatografa%c2%ada-la%c2%adquida-diferentes-sistemas-detectores-y-nuevos-metodos-de-pretratamiento-de-muestra-para-la-determinacion-de-vitaminas-en-alimentos","status":"publish","type":"post","link":"https:\/\/www.deberes.net\/tesis\/quimica-analitica\/hifenaciones-instrumentales-entre-la-cromatografa%c2%ada-la%c2%adquida-diferentes-sistemas-detectores-y-nuevos-metodos-de-pretratamiento-de-muestra-para-la-determinacion-de-vitaminas-en-alimentos\/","title":{"rendered":"Hifenaciones instrumentales entre la cromatograf\u00edal\u00edquida, diferentes sistemas detectores y nuevos m\u00e9todos de pretratamiento de muestra para la determinaci\u00f3n de vitaminas en alimentos"},"content":{"rendered":"<h2>Tesis doctoral de <strong> Mar\u00eda  Angeles Bravo Bravo <\/strong><\/h2>\n<p>El objetivo principal de esta tesis doctoral es desarrollar nuevos m\u00e9todos anal\u00edticos para la determinaci\u00f3n de vitaminas, constituyentes esenciales en la dieta humana. La cromatograf\u00eda l\u00edquida (lc) combinada en l\u00ednea con espectrometr\u00eda de masas (ms) es una de las metodolog\u00edas anal\u00edticas m\u00e1s sensibles y selectivas, y la aplicaci\u00f3n de esta t\u00e9cnica est\u00e1 creciendo r\u00e1pidamente en an\u00e1lisis de alimentos. dependiendo de las estructuras qu\u00edmicas y caracter\u00edsticas anal\u00edticas de los grupos de vitaminas analizados, los m\u00e9todos anal\u00edticos utilizados son hifenaciones de lc con detector de diodos (lc-dad), fluorescencia (lc-fl) y lc-ms.  la metodolog\u00eda utilizada se basa en la aplicaci\u00f3n de nuevos m\u00e9todos de preparaci\u00f3n de la muestra. Los m\u00e9todos cl\u00e1sicos presentan inconvenientes, tales como ser tediosos y largos, y requerir vol\u00famenes grandes de muestra y disolventes t\u00f3xicos. Teniendo como objetivo la qu\u00edmica verde, surgen las t\u00e9cnicas modernas de preparaci\u00f3n de muestra, que ofrecen la posibilidad de automatizaci\u00f3n, son limpias y selectivas, tienen mayor rapidez y eficacia, son baratas, sencillas y sin disolventes t\u00f3xicos. As\u00ed, se ha empleado la extracci\u00f3n l\u00edquida presurizada (ple), que es una tecnolog\u00eda verde emergente. Implica la extracci\u00f3n usando disolventes l\u00edquidos a temperatura y presi\u00f3n elevadas, que aumentan la solubilidad y las propiedades de transferencia de masa. Tambi\u00e9n se ha utilizado la microextracci\u00f3n en fase l\u00edquida (lpme), basada en la extracci\u00f3n de los analitos en una fase l\u00edquida usando cantidades muy peque\u00f1as de disolventes org\u00e1nicos. La microextracci\u00f3n dispersiva l\u00edquido-l\u00edquido (dllme) utiliza un sistema de disolventes ternario. El bajo consumo de tiempo y disolventes org\u00e1nicos son dos de las mayores ventajas de esta t\u00e9cnica. Finalmente, se ha empleado la extracci\u00f3n en fase s\u00f3lida (spe), que implica una partici\u00f3n l\u00edquido-s\u00f3lido, donde la fase extractante es un adsorbente s\u00f3lido, como los nanotubos de carbono. as\u00ed pues, los objetivos de esta tesis doctoral han sido estudiar los acoplamientos instrumentales de lc con detectores dad, fl y ms y procedimientos verdes de tratamiento de la muestra para la determinaci\u00f3n de diferentes vitaminas hidrosolubles y liposolubles en diversos tipos de alimentos. el trabajo se ha dividido en dos partes, en funci\u00f3n del grupo de vitaminas analizado y el tipo de detector empleado. las conclusiones obtenidas son las siguientes: 1. Se han desarrollado m\u00e9todos anal\u00edticos para la determinaci\u00f3n de vitaminas hidrosolubles en alimentos de diferentes tipos, nutrac\u00e9uticos e infantiles. Las vitaminas son cobalaminas, tiamina y sus \u00e9steres y benfotiamina. Son compuestos polares y se analizan por lc en fase reversa con fase estacionaria rp-amida c16 y un encapsulante de trimetilsililo. Las fases m\u00f3viles son mezclas de acetonitrilo y fosfato di\u00e1cido de potasio. Se utiliza dad para cobalaminas o detecci\u00f3n fluorescente para tiamina y sus \u00e9steres y benfotiamina utilizando derivatizaci\u00f3n por oxidaci\u00f3n a tiocromo. 2. Se utilizaron dos procedimientos miniaturizados para el tratamiento de la muestra. Para las cobalaminas se utiliza spe con nanotubos de carbono multipared y un sistema de flujo para la adsorci\u00f3n de los analitos y su eluci\u00f3n con dimetilsulf\u00f3xido. En el caso de la tiamina y benfotiamina se utiliza dllme. 3. La extracci\u00f3n de las vitaminas se lleva a cabo mediante ultrasonidos para cobalaminas o digesti\u00f3n \u00e1cida y extracci\u00f3n enzim\u00e1tica para destruir las formas fosforiladas de las vitaminas b. 4. En la segunda parte de la tesis, se desarrollan m\u00e9todos para determinaci\u00f3n de las cuatro vitaminas liposolubles (a, d, e y k) en alimentos funcionales como zumos de frutas, alimentos vegetales y l\u00e1cteos, y alimentos infantiles. Se analizan por lc en fase reversa o fase normal y diferentes acoplamientos de lc con dad o fluorescencia y ms con interfases esi y apci acoplados a dllme. La extracci\u00f3n se realiza utilizando disolventes org\u00e1nicos, mediante ple o saponificaci\u00f3n alcalina.   palabras clave  cromatograf\u00eda l\u00edquida espectrometr\u00eda de masas detecci\u00f3n por diodos detecci\u00f3n fluorescente pretratamiento de la muestra microextracci\u00f3n dispersiva l\u00edquido-l\u00edquido vitaminas alimentos  the main objective of this thesis, is the development of new analytical methods for the determination of vitamins, essential constituents in the human diet. Liquid chromatography (lc) combined on-line with mass spectrometry (ms) is one of the more sensitive and selective analytical methodologies, and this technique is widely applied in food analysis.  depending on the chemical structures and analytical characteristics of the groups of vitamins analyzed, the analytical methods used are hyphenations of lc with diode array detector (lc-dad), fluorescence (lc-fl) and lc-ms.  the methodology applied is based on the application of new methods for  sample preparation. Classical methods have inconveniences, as being tedious and large, requiring great volumes of sample and toxic organic solvents. With the objective of green chemistry, modern sample preparation techniques appeared, which offer the possibility of automatization, are clean and selective, have higher speed and efficiency, are cheap, simple and without toxic solvents. Thus, pressurized liquid extraction (ple) has been used, being an emergent green technology, based on the extraction using liquid solvents at high temperature and pressure, which increase the solubility and the properties of mass transfer. Liquid-phase microextraction (lpme) was also used and is based on the extraction of the analytes in a liquid phase using very small amounts of organic solvents. Dispersive liquid-liquid microextraction (dllme) uses a ternary solvent system. The low time and organic solvents consume are the two main advantages of this technique. Finally, solid phase extraction (spe) implies a liquid-solid partition, where the extractant phase is a solid sorbent, as multiwalled carbon nanotubes. thus, the objectives of this thesis were to study the instrumental coupling of lc with dad, fl and ms detection and green sample treatment procedures for the determination of several hydrosoluble and liposoluble vitamins in different type of foods. the study is divided in two parts, depending on the group of vitamins analyzed and the type of detector used. the following conclusions have been obtained: 1. Analytical methods are developed for the determination of hydrosoluble vitamins in different type of foods, nutraceuticals and baby foods. The vitamins are cobalamins, thiamine and its esters and benfothiamine. They are polar compounds and are analyzed by lc in reversed phase with a stationary phase rp-amide c16 and an endcapping of trimethylsilyl. The mobile phases are mixtures of acetonitrile and potassium phosphate (ph 7). Dad detection is used for cobalamins or fluorescence for thiamine and its esters and benfothiamine using derivatization by oxidation to thiochrome. 2. Two miniaturized procedures have been developed for the sample treatment. For cobalamins, spe was used with multiwalled carbon nanotubes and a flow system for the adsorption of the analytes and its elution with dimethylsulphoxide. Dllme was used for thiamine and benfothiamine. 3. The extraction of the vitamins was carried out using ultrasounds for cobalamins or acid digestion and enzymatic extraction for destroying the phosphorilated forms of the vitamins b. 4. In the second part of the thesis, new methods are developed for the determination of the four liposoluble vitamins (a, d, e and k) in functional foods as fruit juices, vegetables, milk foods and baby foods. They are analyzed by lc in reversed phase or normal phase and different couplings of lc with dad or fluorescence and ms with interfaces of electrospray ionization (esi) and atmospheric pressure chemical ionization (apci) coupled to dllme. The extraction was carried out using organic solvents, by ple or alkaline saponification.    key words:  liquid chromatography mass spectrometry diode array detection fluorescence detection sample pretreatment dispersive liquid-liquid microextraction vitamins foods<\/p>\n<p>&nbsp;<\/p>\n<h3>Datos acad\u00e9micos de la tesis doctoral \u00ab<strong>Hifenaciones instrumentales entre la cromatograf\u00edal\u00edquida, diferentes sistemas detectores y nuevos m\u00e9todos de pretratamiento de muestra para la determinaci\u00f3n de vitaminas en alimentos<\/strong>\u00ab<\/h3>\n<ul>\n<li><strong>T\u00edtulo de la tesis:<\/strong>\u00a0 Hifenaciones instrumentales entre la cromatograf\u00edal\u00edquida, diferentes sistemas detectores y nuevos m\u00e9todos de pretratamiento de muestra para la determinaci\u00f3n de vitaminas en alimentos <\/li>\n<li><strong>Autor:<\/strong>\u00a0 Mar\u00eda  Angeles Bravo Bravo <\/li>\n<li><strong>Universidad:<\/strong>\u00a0 Murcia<\/li>\n<li><strong>Fecha de lectura de la tesis:<\/strong>\u00a0 13\/12\/2013<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3>Direcci\u00f3n y tribunal<\/h3>\n<ul>\n<li><strong>Director de la tesis<\/strong>\n<ul>\n<li>pelegrin Vi\u00f1as Lopez<\/li>\n<\/ul>\n<\/li>\n<li><strong>Tribunal<\/strong>\n<ul>\n<li>Presidente del tribunal: manuel Hern\u00e1ndez c\u00f3rdoba <\/li>\n<li>Mar\u00eda  soledad Cardenas aranzana (vocal)<\/li>\n<li>Mar\u00eda  del coral Barbas arribas (vocal)<\/li>\n<li>amadeo Rodr\u00edguez fern\u00e1ndez-alba (vocal)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tesis doctoral de Mar\u00eda Angeles Bravo Bravo El objetivo principal de esta tesis doctoral es desarrollar nuevos m\u00e9todos anal\u00edticos para 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