Desarrollo de métodos rápidos y miniaturizados para la determinación de contaminantes orgánicos en muestras ambientales

Resumen

The present PhD work focuses in the development of new, fast, miniaturised sample preparation methods for the determination of trace organic pollutants, i.e., selected persistent organic pollutants (POPs) and pesticides, in environmental and biological samples; and in the evaluation of new chromatographic techniques, such as comprehensive two-dimensional gas chromatography (GC × GC), for the accurate determination of the test compounds in the complex extracts obtained with the previously mentioned generic methods of sample treatment. The first section of this PhD book is an Introduction chapter. The first part of this chapter summarises the physico-chemical properties, origin, main applications, toxicity and, when applicable, current legislative situation of the analytes investigated. Then, an overview of both conventional and miniaturised sample preparation methods in use for the determination of the test analytes in complex (solid and semi-solid) biotic and abiotic matrices is presented. The main practical advantages and limitations of both types of analytical approaches as well as their relative merits for routine analysis are deeply discussed. Finally, after a brief discussion of the main instrumental requirements demanded for this type of determination, a revision of the most representative studies published since the introduction of GC × GC in the environmental field is presented. The objectives of the present work were set on the base of the previous discussion on the current state-of-the-art of both sample preparation methods and GC × GC for the analysis of POPs and pesticides in (semi-)solid environmental and food samples, and are summarised in the second section of this book. The most relevant results concerning the development of fast and miniaturised sample preparation methods for the determination of the selected toxic analytes are presented in the third part of the book. Section 3.1 reports the development and validation of a miniaturized matrix solid phase dispersion (MSPD)-based method for polychlorinated biphenyls (PCBs) determination in fat- containing biotic samples. This method was latter combined with pressurised liquid extraction (PLE) for the analysis of the same analytes in foodstuffs (Section 3.2). A similar approach was used for the analysis of sediments (Section 3.3). In these studies, home-made miniaturized PLE systems were used. One of these PLEs is patent protected (Annex). As regards pesticides, two approaches were assayed. The feasibility of MSPD for miniaturized extraction-plus-purification of selected organophosphorous pesticides, triazines and pyrethroids from fruits was investigated and the most relevant results of this study are summarised in Section 4.2. In an attempt to circumvent one of the most pressing limitations on this method, i.e. the somehow limited repeatability observed for some of the analytes, this method was further combined with ultrasonic extraction. The approach solved the quoted above demand and resulted in an innovative and even faster technique allowing further reduction in solvent consumption. The results of this study are presented in Section 3.4. The fourth section of the book focuses on the evaluation of the relative merits of GC × GC¿¿ECD for the screening of the trace organic pollutants investigated in the complex extracts obtained by applying the generic sample preparation methods developed in the previous parts of this work. Section 4.1 reports the main results obtained when using GC × GC ¿¿ECD for the simultaneous analysis of eight families of POPs (PCBs, PBDEs, PCDDs, PCDFs, PCNs, PCTs, OCPs y toxaphene). Nine column combinations were assayed and critically compared by the analysis of both standard solutions and real-life samples. Using a similar approach, the feasibility of GC × GC ¿¿ECD for simultaneous screening of pesticides (i.e., triazines, pirethroids and organophosphorous pesticides) was also evaluated. Section 4.2 summarises the main conclusions of this study, which includes a critical comparison of this novel method with a more conventional approach based on monodimensional GC couple to mass spectrometry for fruit analysis.