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[EN] This Thesis develops new analytical methods based on the coupling of mass spectrometry ( MS) separation techniques of high efficiency, such as capillary electrophoresis and liquid chromatography applicable to solving problems related to environmental health and occupational , as is the assessment of exogenous and endogenous biomarkers in biological samples , and food quality and safety , through the evaluation and determination of toxic residues in food . Detection was by mass spectrometry applied in various forms (single quadrupole , triple quadrupole , ion trap ) to optimize the detection and identification of analytes , studying the fragmentation processes and transitions that might provide unambiguous identification. From the methodological point of view , the thesis is unified in its approach, because l as methodological innovations that were addressed were focused establishing faster, sensitive and selective analytical methods that can meet the criteria established by the European legislation for validation and quantitative confirmatory methods in the analysis of the analytes of interest. Specifically , this thesis develops new methodologies that span the sample treatment processes (extraction - preconcentration - cleaning) prior to analysis itself in this sense is restricted materials used in on- line settings that facilitate or reduce stages sample treatment . ; [ES] La Tesis presentada está dirigida al desarrollo de nuevos métodos analíticos, basados en el acoplamiento de espectrometría de masas (MS) a técnicas separativas de alta eficacia, como la electroforesis capilar y la cromatografía liquida, aplicables a la resolución de problemas relacionados con la sanidad ambiental y ocupacional, como es la evaluación de biomarcadores exógenos y endógenos en muestras biológicas, y con la calidad y seguridad alimentaria, mediante la evaluación y determinación de residuos tóxicos en alimentos. Se aplicó la detección por espectrometría de masas en sus distintas modalidades (cuadrupolo sencillo, triple cuadrupolo, trampa iónica) para optimizar la detección e identificación de los analitos, estudiando los procesos de fragmentación y las transiciones que pudieron proporcionar una identificación inequívoca. Desde el punto de vista metodológico, la Tesis es unitaria en su planteamiento, ya que l as innovaciones metodológicas que se abordaron estuvieron enfocadas al establecimiento de métodos analíticos más rápidos, sensibles y selectivos, que puedan cumplir los criterios establecidos por la Legislación Europea para su validación como métodos cuantitativos de confirmación en el análisis de los analitos de interés. Concretamente, esta Tesis desarrolla nuevas metodologías que abarcan los procesos de tratamiento de muestra (extracción-preconcentración-limpieza) previos al análisis propiamente dicho; en este sentido se emplearán materiales de acceso restringido, en configuraciones on-line, que faciliten o reduzcan las etapas de tratamiento de muestra. Un segundo enfoque de esta Tesis es el estudio de nuevos mecanismos cromatográficos de separación que permita ampliar el número de compuestos analizables simultáneamente. Este aspecto está dirigido al estudio de la cromatografía de interacciones hidrofílicas (HILIC) y sus posibilidades en la separación de compuestos de elevada polaridad. Un aspecto de gran interés son las posibilidades mostradas de acoplamiento de la cromatografía HILIC a sistemas de cromatografía en fase inversa (RPLC) para posibilitar el estudio simultáneo de metabolitos endógenos (habitualmente compuestos de elevada polaridad) junto a compuestos exógenos utilizados como biomarcadores de exposición a compuestos xenobióticos (de polaridad intermedia y baja) en matrices biológicas.

In recent years, the use of biodegradable fluids as liquid insulation for distribution and power transformers is spreading. The main biodegradable fluids used are natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in leaks, which makes them a suitable solution for applications such as offshore transformers or railway transformers. Additionally, these fluids have a higher flash point than conventional mineral oils, which dramatically reduces the risk of fire and collateral damage derived from explosion and fire. Despite these advantageous factors, there are still some aspects that hinder the broadening of their use, such as the difference in thermal properties or the lack of accepted maintenance procedures for transformers that use them as liquid insulation. This paper presents the current status of biodegradable insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated in order to make them a real alternative to petroleum-based fluids. ; Part of the work was performed during secondments and short visits between University of Valle, University Carlos III of Madrid and University of Cantabria executed in the framework of the BIOTRAFO project "Raising knowledge and developing technology for the design and deployment of high-performance power transformers immersed in biodegradable fluids", H2020-MSCA-RISE-2018- 823969, 2019-21. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 823969. Also, we acknowledge the support of the Spanish Ministry of Science and Innovation by means of the National Research Project Asset management of biodegradable-fluid-based transformers (PID2019-107126RB-C21/AEI/10.13039/501100011033 and PID2019-107126RB-C22/AEI/ 10.13039/501100011033).

In recent years, the use of biodegradable fluids as liquid insulation for distribution and power transformers is spreading. The main biodegradable fluids used are natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in leaks, which makes them a suitable solution for applications such as offshore transformers or railway transformers. Additionally, these fluids have a higher flash point than conventional mineral oils, which dramatically reduces the risk of fire and collateral damage derived from explosion and fire. Despite these advantageous factors, there are still some aspects that hinder the broadening of their use, such as the difference in thermal properties or the lack of accepted maintenance procedures for transformers that use them as liquid insulation. This paper presents the current status of biodegrad able insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated in order to make them a real alternative to petroleum-based fluids. ; Part of the work was performed during secondments and short visits between University of Valle, University Carlos III of Madrid and University of Cantabria executed in the framework of the BIOTRAFO project "Raising knowledge and developing technology for the design and deployment of high-performance power transformers immersed in biodegradable fluids", H2020-MSCA-RISE-2018- 823969, 2019-21. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 823969. Also, we acknowledge the support of the Spanish Ministry of Science and Innovation by means of the National Research Project Asset management of biodegradable-fluid-based transformers (PID2019-107126RB C21/AEI/10.13039/501100011033 and PID2019-107126RB-C22/AEI/ 10.13039/501100011033).

In the last years the use of biodegradable fluids as liquid insulation for distribution and power transformers is becoming more common. The main biodegradable fluids are the natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed as well. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in case of leaks what makes them a suitable solution for some applications, as off-shore transformers or railway transformers. Additionally, these fluids have higher flash point than conventional mineral oils what reduces dramatically the risk of fire and collateral damage derived from explosion and fire. Despite of these advantageous factors, there are still some aspects that hinders the spread of their use, such as the difference on thermal properties, the lack of accepted maintenance procedures and the price. This paper presents the current situation of biodegradable insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated to make them a real alternative to petroleum-based fluids. ; This work was supported in part by the European Union's Horizon 2020 Research and Innovation Programme through the Marie Sklodowska-Curie under Grant 823969, in part by the Ministry of Universities and Innovation Economy through Grants DPI2015-71219-C2 and PID2019-107126RB-C21.

In the last years the use of biodegradable fluids as liquid insulation for distribution and power transformers is becoming more common. The main biodegradable fluids are the natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed as well. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in case of leaks what makes them a suitable solution for some applications, as off-shore transformers or railway transformers. Additionally, these fluids have higher flash point than conventional mineral oils what reduces dramatically the risk of fire and collateral damage derived from explosion and fire. Despite of these advantageous factors, there are still some aspects that hinders the spread of their use, such as the difference on thermal properties, the lack of accepted maintenance procedures and the price. This paper presents the current situation of biodegradable insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated to make them a real alternative to petroleum-based fluids ; This work was supported in part by the European Union's Horizon 2020 Research and Innovation Programme through the Marie Sklodowska-Curie under Grant 823969, in part by the Ministry of Universities and Innovation Economy through Grants DPI2015-71219-C2 and PID2019-107126RB-C21.