The environment is an essential support for human life and ecosystems. Currently, human activities such as agriculture, industry and infrastructure construction, among others, are dangerously affecting the environment, and for this reason continued monitoring may be necessary. To obtain up-to-date information about the state of the environment, the study of different environmental matrices such as water, biota, soils, sediments and air, is essential. In the present Thesis, different methods to determine several contaminants in environmental matrices from different sources have been developed. The methods developed have been addressed by using two approaches: (i) IT-SPME coupled to CapLC and UHPLC with DAD and MS detection, and (ii) in situ analysis devices. The strategy based on the coupling between IT-SPME and CapLC and UHPLC has been utilized to estimate the presence of contaminants (pesticides such as triazines, nitroaniline, phenylureas and organophosphorous, and plasticisers such as degradation products of DEHP and mainly DEHP) in surface water, wastewater from sewage treatment plant, biota and sediments samples. The in situ analyses have allowed the stimation of several contaminants by visual detection or with spectroscopic techniques (FTIR-ATR and UV-Vis spectrophotometry). The pollutants analysed were fat and casein in effluents from dairy industry and the biocide N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine (ADP) in cosmetic wastewaters. Fat has been determined by FTIR-ATR, furthermore casein and ADP have been analysed with a polymeric sensor composed by PDMS, TEOS, NQS and SiO2NPs. On the other hand, the on-site analysis have also been utilized to know damage produced by different pesticides in spinach leaves; for this purpose, a H-point curve isolation method (HPCIM) have been developed to determine Chl a because the content of this pigment is a way to evaluate the health status of plants. The main advantages of the developed procedures in this Thesis are simplicity, sensitivity and also, the sample treatment is reduced to minimum. Furthermore, the methods allow rapid analysis of contaminants in different types of samples. The analysis with coupling IT-SPME-CapLC and IT-SPME-UHPLC can be carried out in less than 30 min. In addition, several samples can be analysed in less than 15 min using the proposed on-site analysis.En la presente Tesis, se han desarrollado diferentes métodos para identificar la presencia de contaminantes procedentes de diferentes fuentes naturales. Los métodos desarrollados han sido abordados utilizando dos metodologías: (i) IT-SPME acoplado a CapLC y UHPLC con detección DAD y MS, y (ii) dispositivos de análisis in situ. La estrategia basada en el acoplamiento entre IT-SPME y CapLC y UHPLC se ha utilizado para la estimación de la presencia de contaminantes (pesticidas como triazinas, nitroanilina, fenilureas y organofosforados, y plastificantes como productos de degradación del DEHP y principalmente DEHP) en muestras de aguas superficiales, de aguas de depuradoras, biota y sedimentos. Los analisis in situ permiten la estimación de varios contaminantes por inspección visual o con técnicas espectroscópicas (FTIR-ATR y UV-Vis). Los contaminantes analizados en efluentes de industrias lácteas fueron grasa y caseína, por otro lado se analizó N-(3-aminopropil)-N-dodecil-1,3-propanediamina (ADP) en aguas residuales procedentes de industrias cosméticas. La grasa se ha determinado con FTIR-ATR, además la caseína y la ADP se han analizado con un sensor polimérico compuesto por PDMS, TEOS, NQS y SiO2NPs. Por otro lado, también se ha utilizado el análisis in situ para conocer el daño producido por diferentes pesticidas a las hojas de espinacas, para ello, se ha desarrollado un método HPCIM para determinar Chl a ya que el contenido de este pigmento es una manera de evaluar el estado de salud de las plantas. Las principales ventajas de los métodos desarrollados en esta Tesis son la simplicidad, sensibilidad y la reducción al mínimo del tratamiento de muestra. Además, los métodos permiten análisis rápidos de contaminantes en diferentes tipos de muestras. El análisis con el acoplamiento IT-SPME-CapLC y IT-SPME-UHPLC se puede llevar a cabo en menos de 30 minutos. Adicionalmente, varias muestras se pueden analizar en menos de 15 minutos utilizando los métodos de análisis in situ propuestos.