Nuevas propuestas de procedimientos analíticos sencillos para la cuantificación de compuestos fenólicos presentes en la fracción minoritaria del aceite de oliva

Abstract

The present thesis is focused on the development of new analytical methodologies for the determination of the phenolic compounds present in the minor fraction of virgin olive oil (VOO). Currently, these compounds are receiving considerable attention, especially due to their antioxidant activity, strongly related to their benefits for the human health. The main goals of the present work have been to improve the already published methodologies, mainly in relation to the simplicity and speed, as well as to develop faster and simpler extraction procedures which, in addition, are environmentally friendly. First of all the identification and quantification of some of these compounds was carried out by non-aqueous capillary electrophoresis coupled to UV-visible diode array detection and fluorescence detection (NACE-DAD-FLD). However, and despite the good results obtained with this method, it was not possible to obtain a good electrophoretic separation between some phenolic acids. To solve this problem, the NACE proposed methodology was combined with the chemometric algorithm multivariate curve resolution-alternating least-squares (MCR-ALS). Afterwards, one of the most important current trends in the evolution of CE, the miniaturised chemical analysis systems, was also investigated. In this line, a new methodology for the determination of three phenolic compounds by microchips electrophoresis coupled to electrochemical detection was developed. On the other hand, the liquid chromatography (LC) technique was also investigated. In this way, the determination of the phenolic compounds in VOO was also performed by conventional LC coupled to DAD and FLD (LC-DAD-FLD) and, in addition, with a rapid resolution column and DAD and mass spectrometry detection (RRLC-DAD-MS). A new reversed phase dispersive liquid-liquid microextraction procedure (RP-DLLME) was developed. It allowed us to carry out the extraction and determination of phenolic compounds from VOO samples in a simpler and faster way, with reproducible and satisfactory results and without consuming high amount of toxic solvents. Finally, the thesis concludes with a novel research related to the characterization and isolation of the phenolic compounds more abundant in VOO and in its semisolid residue (alperujo) by high-speed countercurrent chromatography (HSCCC) and RRLC-DAD-MS/MS for their characterization and quantification.