Estudio químico y estructural en sustancias húmicas

Abstract

Estudio químico y estructural en sustancias húmicas The thesis describes the investigation of the structural and chemical characterisitcs of humic substances in solution. In this way, the complementary use of several analytical techniques show that the macromolecular and the supramolecular (associations of molecules with low molecular wight and size) character are both involved in the humic substances in solution. Furthermore, it is possible to associate the macromolecular or supramolecular patterns with the different fractions of humic substances in solution. Thus, the gray fraction is associated with a clear macromolecular pattern, the brown fraction with both the macromolecular and supramolecular patterns, and the fulvic fraction with the supramlecular pattern. On the other hand, the chemical study of the different fractions of humic substances in solution using different analytical techniques reveals that the gray fraction shows the highest size and a aliphatic character, the brown fraction a medium size and a greater aromatic character and, finally the fulvic fraction the lowest size and an underfined but simple character. In addition, diffusion ordered spectroscopy (DOSY) and Mass spectroscopy (MS) provide low molecular wights to humic substances and therefore it can be deduced that humic substances only show a supramolecular character. But this study indicates that the molecular wight obtained using DOSY is dependent not only on the diffusion coefficient but also on the molecule conformation in solution as well as with the sample concentration. The study using Mass spectroscopy indicates that macromolecular polymers and humic substances show fragmentation and multi charge. Consequently, it is not possible to deduce real molecular wight from the Mass Spectometry