Protecting the environment is an essential task in human societies. The main problem is that the pollution in the different environmental matrices has been increasing for centuries due to the anthropogenic activity of the different sectors (e.g. industry, agriculture, construction, among others). In this scenario and as a result of the advances in scientific fields such as analytical chemistry, “new” contaminants have been found in the environment. However, in some cases this contamination is not recent: modern methods now allow one to detect these substances. Therefore it is not a matter of prevention, but rather adopting the proper strategies, to diminish pollution. These “new pollutants” are called emerging contaminants, a concept that involves many substances: new toxic compounds, the ones recently found in a given matrix or others whose toxic effects have been recently discovered despite their widespread use. On the other hand, known contaminants can have related by-products or derivatives, which can be considered as emerging pollutants. Thus, the problem becomes even more complex as time goes by. Developing methods for characterizing or monitoring this kind of pollutants (i.e. methodologies that allow them to be detected or quantified in a specific environmental compartment) can be seen as the main topic of this Thesis. These methods are highly required and, alongside toxicological and occurrence studies, improve the quality and quantity of the information about emerging contaminants enabling the adoption of appropriate regulatory measures. Different families of emerging contaminants as well as priority pollutants have been studied in this Thesis: pharmaceutical products, pesticides, nanomaterials, surfactants and derivatives of priority contaminants (e.g. polycyclic aromatic hydrocarbons). The analyses have been done in water, soils, sediments and air. To accomplish this, most of the methodologies involve an interesting on-line extraction technique: in-tube solid-phase microextraction coupled to liquid chromatography (i.e. conventional, capillary or nanochromatography). This simple technique, which can be improved by using nanomaterials as adsorbents, enables sample extraction, preconcentration and clean-up processes in a unique system (coupled to separation and detection). Therefore, the main characteristics of the resulting procedures are simplicity, sensitivity and minimum sample handling. New system configurations, methods and materials, as well as improving reported methodologies or applying them for the first time in the analysis of a particular compound are the strategies proposed in this Thesis. All of them are a step forward in the study of emerging contaminants. These substances are far from being eradicated, but they can be better controlled in the environment with strategies such as those mentioned above.El problema de la contaminación ambiental es de una elevada complejidad ya que, además de la gran cantidad de sustancias tóxicas que se analizan y monitorizan en el presente, cada día se originan o se detectan otras y por consiguiente, las soluciones correspondientes parecen ser inalcanzables. La actividad humana en todo los sectores genera contaminantes orgánicos (OCs), algunos de ellos emergentes (ECs), que ponen en riesgo a las diferentes formas de vida a corto, medio y largo plazo. Es más, en algunos casos sólo se han descubierto recientemente los efectos tóxicos de determinados compuestos (pudiendo haber existido exposición a ellos). La legislación a nivel europeo, así como su transposición estatal y autonómica, buscan regular los contaminantes en general de manera progresiva, estableciendo una lista de sustancias prioritarias que pueden ser objeto de modificación y en donde los ECs, luego de los estudios pertinentes, puedan ser incluidos. Todo esto se realiza con el fin de lograr un marco común tanto en Europa (siendo la Directiva Marco del Agua, DMA, un claro ejemplo de ello) como en las diferentes divisiones administrativas de cada país. Sumado a este panorama adverso y a la normativa imperante, la Química Analítica se enfrenta con numerosos inconvenientes. Cada matriz medioambiental (agua, aire, biota, suelos y sedimentos) representa una dificultad por sí misma debido a que posee características particulares que suponen la adopción de una determinada estrategia analítica para estudiar uno o varios analitos contenidos en ella. Por otra parte, ciertos contaminantes se encuentran a niveles traza lo que requiere técnicas de elevada sensibilidad y selectividad. Por lo tanto, desarrollar metodologías eficientes, innovadoras y prácticas para caracterizar, identificar, determinar y por lo tanto, monitorizar OCs (incluidos los ECs) es de una necesidad imperiosa. En este marco, la presente Tesis tiene como objetivo principal el desarrollo de nuevas metodologías que permitan el análisis principalmente de ECs.