Novel monolithic materials for miniaturized separation techniques

In this PhD Thesis novel porous polymer materials and their potential application in miniaturized separation techniques are mainly described. The first section (Chapters 1-3), contains a general introduction, where the impact of monolithic materials (Chapter 2) on chromatography is widely discussed. In Chapter 3, an introduction to the characterization of some polymers and essential oils is presented. Chapters 1-3 were written in compliance with the aforementioned regulation of the University of Valencia, thus constituting the required general introduction. The second part of this PhD Thesis focuses on the preparation, characterization of application of novel monolithic materials to be used in capillary/nano liquid chromatography (c/nano-LC) and in capillary electrochromatography (CEC) as separation media. In these miniaturized LC systems, low flow rates (μL min–1) are used, which implies accurate control of the dead time and delay volumes (which is particularly critical for gradient elution). With this aim, a practical procedure to implement synchronized gradient elution in commercial cLC systems was developed (Chapter 4). The benefits of synchronization on efficiency and time saving were demonstrated. Taking into account this synchronization approach, a method for the determination of parabens in biological fluids was developed. In this method, methacrylate monoliths and nano-LC coupled to mass spectrometry (MS) were used (Chapter 5). The wide variety of easily available chemistries is one of the advantages of polymeric monolithic columns. To obtain monoliths with the desired chromatographic properties, the chemical modification of reactive monoliths is one of the strategies most commonly adopted. Consequently, it is important to know both the number of reactive sites available for functionalization and the functionalization yield. In Chapter 6, a simple gas chromatography – flame ionization detector (GC-FID) method capable of providing this information is described. In the following chapters, different monolithic materials were prepared by chemical modification of its pore surface, in order to achieve stationary phases with enlarged areas and enhanced properties. For this purpose, several ligands as epinephrine (Chapter 7), phosphatidylcholine (Chapter 8), polythiol (Chapter 9), a codeine derivative (Chapter 10), and silver nanoparticles (Chapter 11), among others, have been attached onto the pore surface. In some cases, the enhancement of pore surface coverage with these ligands has provided the highest values published until now. These materials have been successfully applied in the separation of different types of target analytes (alkyl benzenes, aromatic hydrocarbonds, chiral compounds, proteins, etc.). Also, in this second part, the synthesis and applications of hybrid porous polymeric materials using magnetic nanoparticles (Chapter 12) have been described. An enhancement of the surface area of these monoliths with respect to the parent monolith, giving rise to excellent separations of organophosphorous pesticides, has been demonstrated. Finally, in the third part of this PhD Thesis, the characterization of different raw materials by electromigration and chromatographic techniques is described. Within these materials, water soluble polymers such as polyvinyl alcohol (Chapter 13) (used as additive in laundry products) and a rigid polymeric foam (Rohacell®, Chapter 14) which is used in aeronautical and space applications were studied. Also, a method for the analysis of the alcoholic constituents present in essential oils (Chapter 15), of importance in cosmetic and personal care products, was developed.