Complementary analytical platforms for sample treatment and chromatographic determination of contaminants

Abstract

The main objective of this Doctoral Thesis was the development of a complementary analytical platform using different techniques of sample treatment and preconcentration and analytical determination with different separation techniques to achieve the identification and quantification of organic contaminants in different matrices. All the developed methods are applied to analytes and samples whose nature concerns society and which may be regarded as scientific and technological challenges that can be solved. The microextraction techniques simplify the first stage of the analytical process, the sample treatment, meanwhile increasing the sensitivity of the procedures. The application of miniaturized techniques allows to identify the developed methods as environmentally friendly and comply with the principles of Green Analytical Chemistry. The separation of the compounds was carried out using chromatographic techniques, selecting liquid chromatography (LC) or gas chromatography (GC) depending on physical-chemical characteristics of the analytes. Classic injection systems or thermal desorption (TD) injection were used when GC was selected. The developed platform proposes mass spectrometry (MS) for the detection of pollutants, where the most important parameters are the choice of the most suitable ionization source and analyzer, as well as the optimal work conditions that provide maximum sensitivity and selectivity. Therefore, different complementary ways are presented for the determination of organic compounds at trace levels, allowing correctly identification and quantification at very low concentration levels, in order to comply with the limits established in the current European Legislation. The methodology applied in the development of this Doctoral Thesis includes, on the one hand, the optimization of the sample preparation, chromatographic separation and detection stages; and, on the other hand, each optimized method has been validated according to the international guidelines, obtaining the analytical characteristics of the method such as linearity, precision and accuracy parameters. Finally, the analytical methods are applied to the analysis of real samples. The presented Doctoral Thesis was structured according to miniaturized technique applied in the sample treatment. Thus, the first sections focus on the application of dispersive liquid-liquid microextraction (DLLME), which provided the best results in terms of speed, sensitivity and selectivity, obtaining very high preconcentration factors with a very low consumption of organic and sample solvents. The extraction by stir bar sorptive extraction (SBSE) works in the absence of organic solvents, allowing the quantitative transfer of the preconcentrated analytes into the chromatographic system using a thermal desorption unit. Magnetic solid phase extraction (MSPE) was also used, which allows the adsorption of analytes on functionalized magnetic nanoparticles. One of its advantage is the easy isolation using an external magnetic field. Finally, solid phase dispersive extraction (DSPE) technique was applied in order to simplify the matrix of cleaning products, whose complexity does not allow direct analysis. Thus, analytical procedures have been optimized and validated, following the international guides, for the determination of phthalates, alkylphenols and glycol ethers in household cleaning products, new generation pesticides, insecticides (pyrethroids, nicotinoids) and fungicides (triazols, oxazols and strobilurins) in agricultural samples such as water, soils, fruits and vegetables; bisphenols, parabens and ?-dicarbonilic compounds (glyoxal and methylglyoxal) in urine; polycyclic aromatic hydrocarbons in human tissues from autopsies; alkylphenols as food contaminants (fruit juices and infant formulas) and volatile organic compounds (BTEX) in finger paints.